Diamond films were prepared by hot filament chemical vapor deposition (HFCVD) in a gas mixtures system of methane, argon and hydrogen. The composition and morphology in different deposition pressures and filament structures were investigated, as well as the friction and wear-resistant properties. The sp³-bonded content was measured and nano-mechanics properties were also tested. Results of atomic force microscopy and X-ray photoelectron spectroscopy show that the diamond films whose surface roughness is less than 10 nm and sp³-bonded content is greater than 70% can be prepared by bistratal filament structure with optimized proportion of Ar. It is also shown that the friction coefficient of diamond films is 0.13 and its wear-resistant property is excellent. Nano-mechanics of films shows that its elastic modulus is up to 650 MPa and hardness can reach higher than 60 GPa. The diamond films with excellent performance have a broad application prospect in microelectromechanical systems (MEMS).

The meso-macroporous Fe-doped CuO was prepared by a simple hydrothermal method combined with post-annealing. The samples were characterized by X-ray powder diffraction(XRD), scanning electron microscopy(SEM), Brunauer-Emmett-Teller N₂ adsorption-desorption analyses and UV-vis diffuses reflectance spectroscopy. The Fe-doped CuO sample shows higher adsorption capacity and photocatalytic activity for xanthate degradation than pure CuO under visible light irradiation. In addition, the adsorption process is found to fit Langmuir isotherms and pseudo-second-order kinetics. The the first order kinetic Langmuir Hinshelwood model was used to study the reaction kinetics of photocatalytic degradation, and the apparent rate constant ( k ) was calculated. The value of k for Fe-doped CuO is 1.5 times that of pure CuO. The higher photocatalytic activity of Fe-doped CuO is attributed to higher specific surface area together with stronger visible light absorption.

The tensile creep resistance of Mg-5.5%Zn-(0.7%, 1.5%, 3.5%, 7.5%)Y (mass fraction, %) gravity-casting alloys was investigated systematically. The corresponding physical models were established for analyzing the microstructure evolution and creep mechanism. The results show that four second phases are found in Mg-5.5%Zn-(0.7%, 1.5%, 3.5%, 7.5%)Y alloys, including Mg₃ZnY, Mg₃Zn₆Y, Mg₃Zn₃Y₂ and Mg₇Zn₃, where the rare earth rich phase (Mg₃ZnY, Mg₃Zn₆Y, Mg₃Zn₃Y₂) with high melting point can more effectively improve the creep resistance properties of alloys than Mg₇Zn₃. With the increasing of Y content, the creep resistance of alloys is improved correspondingly. The alloys with (1.5%, 3.5%)Y addition exhibit high creep resistance at temperatures from 175 °C to 200 °C and load from 55 MPa to 70 MPa. The 7.5%Y added alloy presents excellent creep resistance even at 275 °C and 55 MPa. The second phase which shows discontinuous distribution at the grain boundary of (0.7%, 1.5%, 3.5%)Y added alloys has preferred orientation and clogs in triple junctions of grain boundary. Simultaneously, the arrangement of second phase particles along tensile direction and the formation of denuded zones are observed during the creep process. Moreover, the crack initiates in these areas and propagates along grain boundary. Compared with discontinuous second phase, the continuous skeleton-like second phase of 7.5%Y added alloy at grain boundary has a better effect on improving the creep resistance properties of alloys.

The microstructure and properties of a quarternary Mg-8Er-5Zn-0.5Zr (mass fraction, %) alloy with the low Er/Zn mass ratio of 1.60 were investigated. It is found that despite of the low Er/Zn mass ratio, the microstructure of the as-prepared alloy is composed of α-Mg, W phase with face-centered cubic structure and long packed stacking ordered (LPSO) phase. As expected, the extruded and annealed alloy possesses high yield stress (310 MPa) and good elongation (14%) at room temperature. The superior mechanical properties can be interpreted in terms of the promising microstructure characteristic of fine a-Mg recrystallized grains embedded with high-density fine lamellar-shaped LPSO phase and block W phase structure.

Hydrogen trapping behavior has been investigated by means of thermal desorption spectroscopy (TDS) for a high strength steel after it was tempered at the temperatures of 430 °C, 500 °C and 520 °C, respectively. The loss of ductility was characterized by slow strain rate test (SSRT) and microscopic observation. It shows that with hydrogen charging the fracture feature transfers from ductile to brittle, resulting in the loss of ductility. Undeformed microstructure immediately beneath the fracture surface in charged specimen corresponds to badly ductility compared to the obviously streamline plastic deformation in uncharged specimen. The activation energies for the peaks present in the TDS analysis are calculated for all tested steel and the activation energies for all temperature peaks are similar, corresponding to the similar types of hydrogen traps.

In order to overcome the nonlinearity of Mises criterion, a new linear yield criterion with a dodecagon shape of the same perimeter as Mises criterion was derived by means of geometrical analysis. Its specific plastic work rate expressed as a linear function of the yield stress, the maximum and minimum strains was also deduced and compared with that of Mises criterion. The physical meaning of the proposed yield criterion is that yielding of materials begins when the shear yield stress τ_s reaches the magnitude of 0.594σ_s. By introducing the Lode parameter, validation of evolution expressions of the proposed yield criterion with those based on Tresca, Mises and TSS criteria as well as available classical yield experimental results of various metals shows that the present results intersect with Mises results and coincide well with experimental data. Moreover, further application to the limit analysis of circle plate as an example is performed to demonstrate the effectiveness of the proposed yield criterion, and the subsequent comparison of limit loads with the Tresca analytical solutions and Mises numerical results shows that the present results are higher than the Tresca analytical results, and are in good agreement with the Mises numerical results.

During the grinding of optical glass, the abrasion directly affects the morphology and depth of subsurface cracks (SSC). The effect of dynamic impact of grinding abrasives on optical glass is an important issue in the field of optics manufacturing. In this work, a single diamond scratch was used to grind optical glass, and grinding parameters were collaboratively controlled to ensure that the cutting layer remained constant. A dynamometer was used to record the duration of the impact process, and the cross-section of the test piece was polished for scanning electron microscopy (SEM) to determine the depth of the SSCs. The experimental results show that as wheel speed increases, SSC depth tends to decrease. When the wheel speed gradually increases from 500 r/min to 2500 r/min, the probability distribution curve for the maximum SSC depth shifts downward by around 80 μm. The effect of the dynamic impact of single diamond scratch is found to be an important cause of SSC formation in optical glass during grinding, i.e., the faster the grinding, the shallower the SSCs.

The role of CaCl₂ during the high temperature chloridizing-reduction roasting process was investigated, aiming at acquiring high strength blast furnace burden with high iron grade and low nonferrous metals content. The effects of CaCl₂ dosage on pelletizing, preheating and reduction were investigated. The results show that CaCl₂ can improve the wet drop strength but reduces the thermostability of pyrite cinder green balls. When the dosage of CaCl₂ exceeds 1%, the compressive strength of preheated pellets decreases while the growth of iron oxide particles is improved. Furthermore, the compressive strength of pre-reduced pellets increases but the metallization degree of pre-reduced pellets decreases with CaCl₂ additive. The removal tests indicate that Zn can be removed completely without CaCl₂ additive, Cu is removed only under the condition with CaCl₂ additive and part of Pb must be removed by CaCl₂ additive.

The yeast Pichia pastoris (P. pastoris) has been used for the expression of heterologous proteins with the significant success. However, it is time-consuming to screen the high expression level of the recombinant P. pastoris directly. Thus, for β-mannanase production, developing the accurate, rapid and inexpensive screening method to substitute random screening is certainly required. A simple method based on the size of hydrolysis hole was described here, but this method was not very accurate that could only be used in preliminary screening. To further improve the accuracy, a micro-plate screening method is established, which appears to be more accurate and effective. The efficiency of this screening method is about 10 times higher than that of the general screening strategy of cultivation in shaking flasks. Two methods presented here can also be used for screening of recombinant Pichia strains with high-level expression of other heterologous protein after modification.

A novel clay mineral biocomposite, chitosan-modified sepiolite (CMSEP), was prepared and used as adsorbent to remove atrazine from water. The adsorption behaviors including thermodynamic and kinetic parameters, effect factors and mechanisms of atrazine adsorption on CMSEP were studied. The results show that the adsorption capacity of atrazine on CMSEP increases with increasing temperature. Protonation of chitosan in biocomposite can improve adsorption ability of the composite to a certain extent. The parameters ΔG^Θ, ΔH^Θ and ΔS^Θ are −1.48—2.69 kJ/mol, 7.54 kJ/mol and 30.28 J/mol, respectively. Langmuir isotherm is proved to describe the adsorption data better than other isotherms with a maximum adsorption capacity of 17.92 mg/g, suggesting that the adsorption process is homogeneous. Pseudo-second-order kinetic model can fit the adsorption kinetic processes well although intraparticle diffusion can not be discarded. Briefly, CMSEP has potential value in the removal of atrazine from water and wastewater.

The white-rot fungus, Phanerochaete chrysosporium (P. chrysosporium), was inoculated during different phases of agricultural waste composting and its effect on the spectroscopic characterization of humic acid (HA) was studied. Three runs were used in this study: Run A was the control without inoculating, and Runs B and C were inoculated P. chrysosporium during the first and the second fermentation phase, respectively. The elemental analysis, ultra-violet spectroscopy (UV), fluorescence spectra, Fourier transform infra-red (FTIR) and ¹³C nuclear magnetic resonance (¹³C-NMR) of HA all lead to the same conclusion, that is, the degree of aromatization and polymerization of HA increases after 42 days composting. However, the inoculation during different phases presents different effects. P. chrysosporium increases the degree of aromatization and polymerization of HA when it is inoculated during the second fermentation phase, while it does not produce an obvious change on the humification degree of HA when it is inoculated during the first fermentation phase.

Nickel is a toxic heavy metal among trace elements which has a detrimental impact on living organisms. There is growing need of finding an economic and effective solution for Ni(II) immobilization in environments. Chinese loess was selected as adsorbent to remove Ni(II) from aqueous solution. Adsorbent dosage, reaction time, solute concentration, temperature, and solution pH also have influences on efficiency of Ni(II) removal. The monolayer adsorption capacity of loess towards Ni(II) is determined to be about 15.61 mg/g. High temperature and pH favor the removal of Ni(II) using Chinese loess soil and the optimal dosage of loess is determined to be 10 g/L. The kinetics and adsorption isotherms of the adsorption process can be best-fitted with the pseudo second order kinetics and Langmuir isothermal model, respectively. The thermodynamic analysis reveals that the adsorption process is spontaneous, endothermic and the system disorder increases with duration. Nickel ions can be removed with the removal efficiency of 98.5% at pH greater than or equal to 9.7. Further studies on loess and Ni(II) laden loess (using X-Ray diffraction, Fourier transform infrared spectroscopy) and Ni(II) species distribution at various pH have been conducted to discuss the adsorption mechanism. Loess soils in China have proven to be a potential adsorbent for Ni(II) removal from aqueous solutions.

The bottom-following problem of an underactuated unmanned undersea vehicle (UUV) is addressed. A robust nonlinear controller is developed by using integral-terminal sliding mode control (ITSMC), which can exponentially drive an UUV onto a predefined path at a constant forward speed. The kinematic error equations are first derived in the Serret-Frenet frame. Using the line of sight (LOS) method, Lyapunov’s direct technique and tracking differentiator, the guidance law is established. Then, the kinematic controller, the guidance law, is expanded to cope with vehicle dynamics by resorting to introduce two integral-terminal sliding surfaces. Robustness to parameter perturbation is addressed by incorporating the reaching laws associated with the upper bound of the parameter perturbation. The proposed control law can guarantee that all error signals globally exponentially converge to the origin. Finally, a series of numerical simulation results are presented and discussed. In these simulations, wave, constant unknown ocean currents (for the purposes of the controller) and the parameter perturbation are added to illustrate the robustness and effectiveness of the bottom-following control scheme.

To increase the efficiency and reliability of the thermodynamics analysis of the spool valve, the precise function expression of the flow area for the sloping U-shape notch orifice versus the spool stroke and thermal-hydraulic bond graph based on the conservation of mass and energy were introduced. Subsequently, the connection rule for the bond graph elements and the method to construct the complete thermal-hydraulic system model were proposed. On the basis of heat transfer analysis of a typical hydraulic circuit containing the spool valve, the lumped parameter for mathematical model of the system was given. At last, the reliability of the mathematical model of the flow area and the thermal-hydraulic system for the sloping U-shape notch orifice on the spool were demonstrated by the test. The good agreement between the simulation results and experimental data demonstrates the validity of the modeling method.

In order to enhance the atomization efficiency of atomizer, a new type of wind-spray dust controller combining the rotary-atomization and colliding broken of droplets was designed by the method of opening the water circulation within the blades. The experiment test for dust controller was conducted by adjusting the following parameters: rotating speed, diversion hole-exit diameter, and colliding tooth angle. Results show that the atomization efficiency increases firstly then decreases with them. And the optimal parameters are obtained with rotating speed 1500-2200 r/min, diversion hole-exit diameter 2-2.5 mm and colliding tooth angle 30°-40°, and under these conditions the corresponding atomization efficiency tops to 95%. Then, the atomization situation under the optimal parameters is held from the aspect of simulation internal flow field and the results of droplet size (30-80 µm) are got, which indicates that the conclusion on the optimized parameters of dust controller is reasonable. The collecting efficiencies of different dust concentrations are determined, ranging from 85% to 98.4%, which shows that the designed dust controller can obtain a good atomizing effect and achieve well dustfall efficiency for the wetting dust control of coal mine.

For the static analysis of the sinking stage curved beam, a finite difference model was presented based on the proposed revised Vlasov equations. First, revised Vlasov equations for thin-walled curved beams with closed sections were deduced considering the shear strain on the mid-surface of the cross-section. Then, the finite difference formulation of revised Vlasov equations was implemented with the parabolic interpolation based on Taylor series. At last, the finite difference model was built by substituting geometry and boundary conditions of the sinking stage curved beam into the finite difference formulation. The validity of present work is confirmed by the published literature and ANSYS simulation results. It can be concluded that revised Vlasov equations are more accurate than the original one in the analysis of thin-walled beams with closed sections, and that present finite difference model is applicable in the evaluation of the sinking stage curved beam.

The contact strength calculation of two curved rough surfaces is a forefront issue of Hertz contact theory and method. Associated rules between rough surface characterization parameters (correlation length, and root mean square deviation) and contact characteristic parameters (contact area, maximum contact pressure, contact number, and contact width) of two rough cylinders are mainly studied. The contact model of rough cylinders is deduced based on GW model. As there is no analytical solution for the pressure distribution equation, an approximate iterative solution method for the pressure distribution is adopted. Furthermore, the quantitative relationships among the correlation length, the root mean square deviation, the asperity radius of curvature and the asperity density are also obtained based on a numerical simulation method. The maximum contact pressure and the contact number decrease with the increase of correlation length, while the contact width and the contact area are on the contrary. The contact width increases with the increase of root mean square deviation while the maximum contact pressure, the contact area and the contact number decrease.

Nondominated sorting genetic algorithm II (NSGA-II) is well known for engine optimization problem. Artificial neural networks (ANNs) followed by multi-objective optimization including a NSGA-II and strength pareto evolutionary algorithm (SPEA2) were used to optimize the operating parameters of a compression ignition (CI) heavy-duty diesel engine. First, a multi-layer perception (MLP) network was used for the ANN modeling and the back propagation algorithm was utilized as training algorithm. Then, two different multi-objective evolutionary algorithms were implemented to determine the optimal engine parameters. The objective of the present study is to decide which algorithm is preferable in terms of performance in engine emission and fuel consumption optimization problem.

Aggregate nearest neighbor (ANN) search retrieves for two spatial datasets T and Q, segment(s) of one or more trajectories from the set T having minimum aggregate distance to points in Q. When interacting with large amounts of trajectories, this process would be very time-consuming due to consecutive page loads. An approximate method for finding segments with minimum aggregate distance is proposed which can improve the response time. In order to index large volumes of trajectories, scalable and efficient trajectory index (SETI) structure is used. But some refinements are provided to temporal index of SETI to improve the performance of proposed method. The experiments were performed with different number of query points and percentages of dataset. It is shown that proposed method besides having an acceptable precision, can reduce the computation time significantly. It is also shown that the main fraction of search time among load time, ANN and computing convex and centroid, is related to ANN.

The problem of fault estimation is investigated for a class of uncertain switched systems with time-varying delay. A robust observer-based fault estimator is designed such that the augment error system is exponentially stable and the H_∞ performance index meets the predefined requirements. Based on the multiple Lyapunov-Krasovskii functions and the average dwell-time method, the delay dependent sufficient conditions on the existence of desired fault estimator are established. However, since these conditions are not linear matrix inequalities (LMIS), they can not be solved by MATLAB. By using a novel method, these conditions are presented in terms of LMIS. Finally, a numerical example is carried out. The designed fault estimator could tract the fault signal timely. Besides, the error between estimation and fault is very small. Therefore, the validity of the obtained results is illustrated.

As unmanned aerial vehicles (UAVs) are used more and more in military operations, increasing their level of autonomous decision making becomes necessary. In uncertain battlefield environments, when making sovereign decisions, UAVs must choose low-risk options. An integrated framework is proposed for UAV robust decision making in air-to-ground attack missions under severe uncertainty. In the offline part of the framework, the battlefield scenarios are analyzed and an influence diagram is built to represent the decision situation. In the online part, the UAV evaluates the alternative actions for every scenario, and then the optimal robust action is chosen, using the robust decision model. Results of simulation show that the proposed approach is feasible and effective. The framework can support UAVs in making independent robust decisions under circumstances which require immediate responses under severe uncertainty, and it can also be extended to applications in more complex situations.

Parkam (Sarah) porphyry system is located on the metallogenic belt of Kerman, Iran. Due to existence of some copper-rich resources in this region, finding out the exact statistical characteristics such as distribution of data population, mean, variance and data population behavior of elements like Cu, Mo, Pb and Zn is necessary for interpreting their geological behavior. For this reason, precise calculation of statistical characteristics of Pb and Zn grade datasets was performed and results were interpreted geologically. The natures of Pb and Zn distributions were initially identified and their distributions were normalized through statistical treatment. Subsequently, the variograms were calculated for each exploration borehole and show that both Pb and Zn geochemical variates are spatially correlated. According to the similarity of the behavior of Pb and Zn in these calculations, it is decided to measure their exact behavior applying K-means clustering method. K-means clustering results show that the Zn grade varies linearly relative to that of Pb values and their behavior is similar. Based on the geochemical behavior similarity of Pb and Zn, throughout the pervasive secondary hydrothermal activity, they are remobilized in the similar manner, from the deep to the shallow levels of the mineralization zones. However, statistical analysis suggests that hydrothermal activity associated with secondary waters in Parkam is effective in remobilizing and enriching both Pb and Zn since they have similar geochemical characteristics. However, the process does not result in generation of economic concentrations.

Tunnels are one of the major transportation routes to pass mountains and difficult geological conditions. The behavior of these structures is significantly influenced by rock mass and discontinuities. Orientation of discontinuities is one of the most important geometrical parameters affecting discontinuities behavior. The effect of large discontinuities (faults) behavior on a jointed medium around rectangular tunnels is studied. A hybridized indirect boundary element code named TFSDDM (fictitious stress displacement discontinuity method) is used to study the stress distribution around the tunnels excavated in jointed rock masses. The code uses advantages of both fictitious stress and displacement discontinuity methods to analyze discontinuity effects more accurately. Results show that the dip angle of discontinuities has significant effect on stress distribution around the tunnel. It is also shown that increase in the discontinuities dip angle located in the roof will result in decrease in tensile stress of the roof. Stresses reaches to 8 MPa in the roof while due to dilation effect they reach up to 13 MPa.

Tunnelling-induced long-term consolidation settlement attracts a great interest of engineering practice. The distribution and magnitude of tunnelling-induced initial excess pore water pressure have significant effects on the long-term consolidation settlement. A simple and reliable method for predicting the tunnel-induced initial excess pore water pressure calculation in soft clay is proposed. This method is based on the theory of elasticity and SKEMPTON’s excess pore water pressure theory. Compared with the previously published field measurements and the finite-element modelling results, it is found that the suggested initial excess pore water pressure theory is in a good agreement with the measurements and the FE results. A series of parametric analyses are also carried out to investigate the influences of different factors on the distribution and magnitude of the initial excess pore water pressure in soft ground.

A joined failure mechanism of translation and rotation was proposed for the stability analysis of deep tunnel face, and the upper bound solution of supporting force of deep tunnel was calculated under pore water pressure. The calculations were based on limit analysis method of upper bound theory, with the employment of non-associated Mohr-Coulomb flow rule. Nonlinear failure criterion was adopted. Optimized analysis was conducted for the effects of the tunnel depth, pore water pressure coefficient, the initial cohesive force and nonlinear coefficient on supporting force. The upper bound solutions are obtained by optimum method. Results are listed and compared with the previously published solutions for the verification of correctness and effectiveness. The failure shapes are presented, and results are discussed for different pore water pressure coefficients and nonlinear coefficients of tunnel face.

Based on three different kinds of conductive paths in microstructure of soil and theory of electrochemical impedance spectroscopy (EIS), an integrated equivalent circuit model and impedance formula for soils were proposed, which contain 6 meaningful resistance and reactance parameters. Considering the conductive properties of soils and dispersion effects, mathematical equations for impedance under various circuit models were deduced and studied. The mathematical expression presents two semicircles for theoretical EIS Nyquist spectrum, in which the center of one semicircle is degraded to simply the equivalent model. Based on the measured parameters of EIS Nyquist spectrum, meaningful soil parameters can easily be determined. Additionally, EIS was used to investigate the soil properties with different water contents along with the mathematical relationships and mechanism between the physical parameters and water content. Magnitude of the impedance decreases with the increase of testing frequency and water content for Bode graphs. The proposed model would help us to better understand the soil microstructure and properties and offer more reasonable explanations for EIS spectra.

A small-scale physical modelling method was developed to investigate the pile bearing capacity and the soil displacement around the pile using transparent soil and particle image velocimetry (PIV) technique. Transparent sand was made of baked quartz and a pore fluid with a matching refractive index. The physical modelling system consists of a loading system, a laser light, a CCD camera, an optical platform and a computer for image analyzing. A distinctive laser speckle was generated by the interaction between the laser light and transparent soil. Two laser speckle images before and after deformation were used to calculate the soil displacement field using PIV. Two pipe piles with different diameters under oblique pullout loads at angles of 0°, 30°, 45°, 60° and 90° were used in tests. The load-displacement response, oblique pullout ultimate resistances and soil displacement fields were then studied. The test results show that the developed physical modelling method and transparent soil are suitable for pile-soil interaction problems. The soil displacements around the pipe piles will improve the understanding on the capacity of pipe piles under oblique pullout loads.

The extended finite element method (XFEM) is a numerical method for modeling discontinuities within the classical finite element framework. The computation mesh in XFEM is independent of the discontinuities, such that remeshing for moving discontinuities can be overcome. The extended finite element method is presented for hydro-mechanical modeling of impermeable discontinuities in rock. The governing equation of XFEM for hydraulic fracture modeling is derived by the virtual work principle of the fracture problem considering the water pressure on crack surface. The coupling relationship between water pressure gradient on crack surface and fracture opening width is obtained by semi-analytical and semi-numerical method. This method simplifies coupling analysis iteration and improves computational precision. Finally, the efficiency of the proposed method for modeling hydraulic fracture problems is verified by two examples and the advantages of the XFEM for hydraulic fracturing analysis are displayed.

It is widely believed that hydraulic fracturing will occur in the clay core of an earth-rockfill dam if the water pressure in the core increases to levels that are high enough to allow a fracture to form. An elastic-plastic solution to critical water pressure inducing hydraulic fracturing (fracture initiation pressure) in soil is derived based on Mohr-Coulomb shear failure criterion and the theory of cavity expansion. In order to verify the applicability of the criteria presented and study the relations among fracture initiation pressure, tensile strength and stress state of soil, laboratory tests are performed on compacted cuboid specimens by true triaxial apparatus. According to the test results, the cracks of hydraulic fracturing existed perpendicular to the minor principal stress plane. The hydraulic fracturing pressure p_f increases with the increase of dry density of specimen, p_f shows good linear relationship with σ₂ and σ₃. The prediction from presented equation is compared with test results and other three predictions, of which two are tensile failure (TS) criterion, and the other is Mohr-Coulomb (M-C) criterion. The presented solution is verified, and the other three approaches for p_f are evaluated. The comparison indicates that the predicted values from the presented equations agree well with the test values for specimens of low dry density, and the error of the prediction is larger for those of high dry density, especially in lower minor stress states. The predicted average relative error of absolute value R_a from TS1 criterion is 13.3% for all specimens of different dry densities, and each prediction is lower than the test data. On the contrary, most of the predicted values from M-C criterion are greater than the test data, but the average relative error from the presented equation is the minimum. Considering the safety of soil works, an equation from TS1 criterion is suggested to evaluate the occurrence of hydraulic fracturing in earth-rockfill dam designing.

When an expanded-base pile is installed into ground, the cavity expansion associated with penetration of the enlarged pile base is followed by cavity contraction along the smaller-diameter pile shaft. In order to account for the influence of cavity contraction on the change of bearing capacity of expanded-base pile, a theoretical calculation methodology, predicting the setup of expanded-base pile, was established by employing the cavity contraction theory to estimate the shaft resistance of expanded-base pile, and horizontal consolidation theory to predict the dissipation of excess pore pressure. Finally, the numerical solutions for the setup of expanded-base pile were obtained. The parametric study about the influence of cavity contraction on setup of expanded-base pile was carried out, while a field test was introduced. The parametric study shows that the decrements in radial pressure and the maximum pore water pressure after considering cavity contraction are increased as the expanded ratio (base diameter/shaft diameter) and rigidity index of soil are raised. The comparison between calculated and measured values shows that the calculated results of ultimate bearing capacity for expanded-base pile considering cavity contraction agree well with the measured values; however, the computations ignoring cavity contraction are 2.5-3.0 times the measured values.

The current temperature field model of mine gob does not take the boundary conditions of the atmospheric pressure into account, while the actual atmospheric pressure is influenced by weather, so as to produce differences between ventilation negative pressure of the working face and the negative pressure of gas drainage in gob, thus interfering the calculated results of gob temperature field. According to the characteristics of the actual air flow and temperature change in gob, a two-dimensional temperature field model of the gob was built, and the relational model between the air pressure of intake and outlet of the gob and the atmospheric pressure was established, which was introduced into the boundary conditions of temperature field to conduct calculation. By means of analysis on the simulation example, and comparison with the traditional model, the results indicate that atmospheric pressure change had notable impact on the distribution of gob temperature field. The laboratory test system of gob temperature field was constructed, and the relative error between simulated and measured value was no greater than 9.6%, which verified the effectiveness of the proposed model. This work offers theoretical basis for accurate calculation of temperature and prediction of ignition source in mine gob, and has important implications on preventing spontaneous combustion of coal.

Numerical investigation was performed to examine the effect of rear barrier pillar on stress distribution around a longwall face. Salamon theoretical formula was used to calculate the parameters of the caving zone, which was later assigned to double yield constitutive model in FLAC^3D. Numerical results demonstrate that high stress concentration zone exists above the region where the second open-off cut intersects with the rear barrier pillar due to stress transfer and plastic zone expansion. It is also found that the maximum vertical stresses with varied distance to the seam floor are all within the projective plane of the rear barrier pillar and their positions concentrate on the barrier pillar adjacent to the connection corner of the second open-off cut. In addition, position of the maximum vertical stresses abruptly transfer from the connection corner adjacent to former panel to that adjacent to current panel along the panel direction.

A roadway within ultra-close multiple-seams (RUCMSs) is one of the most difficult supported coal roadways to deal with in underground coal mines. This is usually due to the unknown stress distributions, improper roadway layout, and unreasonable support parameters. In order to solve this support problem and effectively save RUCMSs from frequent and abrupt disasters (such as serious deformation of the surrounding rock, roof cave ins, and coal side collapse), a comprehensive method is adopted here which includes theoretical analysis, numerical simulation, and field monitoring. A mechanical model was constructed to determine the stress distribution in the coal pillar after two sides of a longwall panel had been mined. Based on this model, the horizontal, vertical, and tangential stress equations for the plane below the floor of the upper-left coal pillar were deduced. In addition, a typical coal mine (the Jinggonger colliery, located in Shuozhou city, Shanxi province, China) with an average distance between its 9# and 11# coal seams of less than 8.0 was chosen to conduct research on the proper layout and reasonable support required for a typical coal roadway located within coal seam 11#. Using FLAC^3D (Fast Lagrangian Analysis of Continua in 3-Dimensions) numerical software, eight schemes were designed with different horizontal distances (d) between the center lines of the coal pillar and the roadway in the lower coal seam (RLCS). The simulations and detailed analysis indicate that the proper distances required are between 22.5 and 27.5 m. A total of 20 simulation schemes were used to investigate the factors influencing the support provided by the key bolts (bolt length, spacing, distance between two rows, installation angle, and pre-tightening force). The results were analyzed and used to determine reasonable values for the support parameters. Field results show that the stability and strength of the RLCS can be effectively safeguarded using a combination of researched stress distribution characteristics, proper layout of the RLCS, and correct support parameters.

Steel-concrete composite frames are seeing increased use in earthquake region because of their excellent structural characteristics, including high strength, stiffness, and good ductility. However, there exist gaps in the knowledge of seismic behavior and the design provisions for these structures. In order to better understand the seismic behaviors of composite frame systems, eight steel-concrete composite frames were designed. These composite frames were composed of steel-concrete composite beams and concrete filled steel tube columns. The axial compression ratio of column, slenderness ratio and linear stiffness ratio of beam to column were selected as main design parameters. The low reversed cyclic loading tests of composite frame system were carried out. Based on test results, the seismic behaviors of composite frames such as failure mode, hysteresis curve, strength degradation, rigidity degradation, ductility and energy dissipation were studied. Known from the test phenomenon, the main cause of damage is the out-of-plane deformation of steel beam and the yielding destruction of column heel. The hysteretic loops of composite frame appear a spindle shape and no obvious pinch phenomenon. The results demonstrate that this type of composite frame has favorable seismic behaviors. Furthermore, the effects of design parameters on seismic behaviors were also discussed. The results of the experiment show that the different design parameter has different influence rule on seismic behaviors of composite frame.

A novel hybrid FRP-aluminum space truss was employed in a two-rut modular bridge superstructure, which is composed of standard structural units. The main objective of this work was to obtain a simple analytical solution that can conveniently predict the deflection of the proposed hybrid space truss bridge. The analytical formulae are expected to possess a straightforward format and simple calculation process. A simple description of the proposed bridge was introduced. The design formulae of the deflection were derived based on a simplified analytical plane truss model, which possessed hinge nodes and was subsequently simplified as two solid web beams during the theoretical derivation process. To validate the analytical model and formulae, numerical and experimental works were conducted and compared with the theoretical solutions. The results indicate that the analytical formulae provide higher deflection magnitudes with a difference of <1.5% compared with the experiments performed and <4.5% compared with the FE model used; the simplified plane truss is thus shown to be an effective analytical model for the derivation of deflection design formulae, which can conveniently calculate the deflection of the hybrid space truss bridge with satisfactory accuracy.

The hollow centre cracked disc (HCCD) specimen is one of the suggested alternative methods for determining the fracture toughness of rock. This work aims to investigate the fracture mechanism in HCCD in macro- and micro-scales using numerical methods, extended finite element method (X-FEM) and particle flow code (PFC) modeling, respectively. In the X-FEM, heaviside and near-tip enrichment functions are employed to consider the presence of the crack in the model. In PFC modeling the movement and interaction of stressed assemblies of rigid spherical particles are modeled using the distinct element method (DEM). A numerical code called MEX-FEM based on XFEM has been developed to simulate the problems involving crack. The models of pure modes I and II in macro-scale are simulated in micro-scale. The results show that dimensionless stress intensity factors (Y_I, Y_II) for pure modes I and II increase by increasing the crack length ratio. The angle at which the pure mode II occurs decreases by increasing the crack length ratio. In mixed mode I-II, The value of Y_I decreases by increasing the crack angle, while the value of Y_II increases to a given crack angle and then it decreases. Moreover, the fracture in micro-scale, unlike the macro-scale, includes a combination of different modes of fracturing.

A three-dimensional dynamic finite element model of track-ballast-embankment and piled raft foundation system is established. Dynamic response of a railway embankment to a high-speed train is simulated for two cases: soft ground improved by piled raft foundation, and untreated soft ground. The obtained results are compared both in time domain and frequency domain to evaluate the effectiveness of the ground improvement in mitigating the embankment vibrations induced by high-speed trains. The results show that ground improving methods can significantly reduce the embankment vibrations at all considered train speeds (36- 432 km/h). The ground response to a moving load is dictated largely by the relationship between load speed and characteristic value of wave velocities of the ground medium. At low speeds, the ground response from a moving load is essentially quasi-static. That is, the displacements fields are essential the static fields under the load simply moving with it. For the soft ground, the displacement on the ballast surface is large at all observed train speeds. For the model case where the ground is improved by piled raft foundation, the peak displacement is reduced at all considered train speeds compared with the case without ground improvement. Based on the effect of energy-dissipating of ballast-embankment-ground system with damping, the train-induced vibration waves moving in ballast and embankment are trapped and dissipated, and thus the vibration amplitudes of dynamic displacement outside the embankment are significantly reduced. But for the vibration amplitude of dynamic velocity, the vibration waves in embankment are absorbed or reflected back, and the velocity amplitudes at the ballast and embankment surface are enhanced. For the change of the vibration character of embankment and ballast, the bearing capacity and dynamic character are improved. Therefore, both of the static and dynamic displacements are reduced by ground improvement; the dynamic velocity of ballast and embankment increases with the increase of train speed and its vibration noise is another issue of concern that should be carefully evaluated because it is associated with the running safety and comfort of high-speed trains.

In order to explore the pressure relief and structure stability mechanism of lateral cantilever structure in the stope under the direct coverage of thick hard roof and its impact on the gob-side entry retaining, a lateral cantilever fractured structural mechanical model was established on the basis of clarification for the stress environment of gob-side entry retaining, and the equation of roof given deformation and the balance judgment for fracture block were obtained. The optimal cantilever length was proposed based on the comparison of roof structural characteristics and the stress, deformation law of surrounding rocks under six different cantilever lengths by numerical simulation method. Double stress peaks exist on the sides of gob-side entry retaining and the entry located in the low stress area. The pressure of gob-side entry retaining can be relieved by reducing the cantilever length. However, due to the impact of arch structure of rock beam, unduly short cantilever would result in insufficient pressure relief and unduly long cantilever would bring larger roof stress which results in intense deformation. Therefore, there is optimal cantilever length, which was 7-8 m in this project that enables to achieve the minimum deformation and the most stabilized rock structure of entry retaining. An engineering case of gob-side entry retaining with the direct coverage of 10 m thick hard limestone roof was put forward, and the measured data verified the reasonability of conclusion.

Taking wall-flow diesel particulate filter (DPF) as the research objective and separately assuming its filtering wall to be composed of numerous spherical or cylindrical elements, two different mathematical models of steady filtration for wall-flow diesel particulate filter were developed and verified by experiments as well as numerically solved. Furthermore, the effects of the macroand micro-structural parameters of filtering wall and exhaust-flow characteristic parameters on trapping efficiency were also analyzed and researched. The results show that: 1) The two developed mathematical models are consistent with the prediction of variation of particulate size; the influence of various factors on the steady trapping efficiency is exactly the same. Compared to model 2, model 1 is more suitable for describing the steady filtration process of wall-flow diesel particulate filter; 2)The major influencing factors on steady trapping efficiency of wall-flow diesel particulate filter are the macro-and micro-structural parameters of filtering wall; and the secondary influencing factors are the exhaust-flow characteristic parameters and macro-structural parameters of filter; 3)The steady trapping efficiency will be improved by increasing filter body volume, pore density as well as wall thickness and by decreasing exhaust-flow, but effects will be weakened when particulate size exceeds a certain critical value; 4) The steady trapping efficiency will be significantly improved by increasing exhaust-flow temperature and filtering wall thickness, but effects will be also weakened when particulate size exceeds a certain critical value; 5) The steady trapping efficiency will approximately linearly increase with reducing porosity, micropore aperture and pore width.

Peristalsis of Carreau-Yasuda fluid is investigated. Analysis is carried out in the presence of velocity slip and convective boundary conditions. Thermal conductivity of the fluid is taken to be temperature dependent. Lubrication analysis is used in the formulation of the problem. Resulting nonlinear system of equations is solved numerically. Impact of embedded parameters on the quantities of interest is examined through graphs and tables. Comparison of the behavior of the Carreau-Yasuda, Carreau and Newtonian fluid models is presented. Results show that the heat transfer rate at the wall for the Carreau fluid model is large when compared with the Newtonian or the Carreau-Yasuda fluid model. Also the heat transfer rate at the wall decreases with increase in the velocity slip and variable thermal conductivity parameters. Further, an increase in the Biot number reduces the fluid temperature by a considerable amount.

The relationships among compression ratio and stress, compression ratio and residual oil of cake in pressing process of castor beans were studied using the test equipment under different states of oilseeds and ways of pressing manners. The results show that variation of stress increases nonlinearly and residual oil rate decreases with the increase of compression ratio. Lower residual oil of cake was obtained by pressing gently and frequently. Curve fitting on both relationships had been built and parameters for the model were obtained by least square procedure and deepening research on pressing process of the castor beans for castor oil. By assuming that the value of oil production is equivalent to the value of energy consumption, the critical compression ratio of intact seeds is 6.2 while that of crushed seeds is 3.6.

Open-graded friction course (OGFC) is applied to pavement surfaces to increase driving safety under wet conditions, and recently, to reduce tire/pavement noise. The durability of OGFC, however, has been a concern since conventional OGFC mixes last typically less than ten years before major maintenance or rehabilitation is needed. This work investigates a new open-graded asphalt mixture that uses epoxy asphalt as binder to improve mix durability. One type of epoxy asphalt that has been successfully applied to dense-graded asphalt concrete for bridge deck paving was selected. A procedure of compacting the mix into slab specimens was developed and a series of laboratory tests were conducted to evaluate the performance of the new mix, including Cantabro loss, permeability, friction, shear strength, and wheel rutting tests. Results show superior overall performance of the open-graded epoxy asphalt mix compared to conventional open-graded asphalt mix. There are also preliminary indications that the OGFC mix with 4.75-mm NMAS gradation can improve the resistance performance to raveling, while the OGFC mix with 9.5-mm NMAS gradation can improve the performance of surface friction at a high slip speed.

An improved social force model based on exit selection is proposed to simulate pedestrians’ microscopic behaviors in subway station. The modification lies in considering three factors of spatial distance, occupant density and exit width. In addition, the problem of pedestrians selecting exit frequently is solved as follows: not changing to other exits in the affected area of one exit, using the probability of remaining preceding exit and invoking function of exit selection after several simulation steps. Pedestrians in subway station have some special characteristics, such as explicit destinations, different familiarities with subway station. Finally, Beijing Zoo Subway Station is taken as an example and the feasibility of the model results is verified through the comparison of the actual data and simulation data. The simulation results show that the improved model can depict the microscopic behaviors of pedestrians in subway station.

The major objective of this work was to establish a structural state-space model to estimate the dynamic origin-destination (O-D) matrices for urban rail transit network, using in- and out-flows at each station from automatic fare collection (AFC) system as the real time observed passenger flow counts. For lacking of measurable passenger flow information, the proposed model employs priori O-D matrices and travel time distribution from historical travel records in AFC system to establish the dynamic system equations. An arriving rate based on travel time distribution is defined to identify the dynamic interrelations between time-varying O-D flows and observed flows, which greatly decreases the computational complexity and improve the model’s applicability for large-scale network. This methodology is tested in a real transit network from Beijing subway network in China through comparing the predicted matrices with the true matrices. Case study results indicate that the proposed model is effective and applicative for estimating dynamic O-D matrices for large-scale rail transit network.