The effectiveness of optimizing electrical conductivity of carbon fiber/carbon nanotube (CNT)/epoxy hybrid composites via Taguchi method was demonstrated. CNTs were induced on carbon fabric by electrophoretic deposition (EPD) technique. The essential deposition parameters were identified as 1) the deposition time, 2) the deposition voltage, 3) the mass fraction of CNTs in suspension, and 4) the distance between the electrodes. An experimental design was then performed to establish the appropriate levels for each factor. An orthogonal array of L₉ (3⁴) was designed to conduct the experiments. Electrical conductivity results were collected as the response. The relative influences of design parameters on the response were discussed. Using the model, signal to noise (S/N) ratio and response characteristics for the optimized deposition parameter combination were predicted. The results show clearly that the optimum condition of electrophoretic deposition (EPD) process improves the electrical conductivity of carbon/epoxy hybrid composites.

An effective approach was conducted for estimating fracture toughness using the crack opening displacement (COD) method for plasma enhanced chemical vapor deposition (PECVD) coating materials. For this evaluation, an elastoplastic analysis was used to estimate critical COD values for single edge notched bending (SENB) specimens. The relationship between fracture toughness (K_IC) and critical COD for SENB specimens was obtained. Microstructure of the interface between Al₂O₃-TiO₂ composite ceramic coatings and AISI 1045 steel substrates was studied by using scanning electron microscope (SEM). Chemical compositions were clarified by energy-dispersive X-ray spectroscopy (EDS). The results show that the interface between of Al₂O₃-TiO₂ and substrate has mechanical combining. The nanohardness of the coatings can reach 1 200 GPa examined by nanoindentation. The K_IC was calculated according to this relationship from critical COD. The bending process produces a significant relationship of COD independent of the axial force applied. Fractographic analysis was conducted to determine the crack length. From the physical analysis of nanoindentation curves, the elastic modulus of 1045/Al₂O₃-TiO₂ is 180 GPa for the 50 μm film. The highest value of fracture toughness for 1045/Al₂O₃-TiO₂-250 μm is 348 MPa·m^l/2.

An Al coating on Mg substrate was achieved by droplet spraying treatment. The microstructure was studied by electron probe microanalysis (EPMA) and X-ray diffraction (XRD). The coating layer is composed of Al phase and exhibits superior corrosion resistance. The formation of the coating is mainly attributed to the obstruction of expansion of the transition zone by primarily solidified Mg₁₇Al₁₂ during rapid cooling, and the diffusion is restricted in a thin layer. These results show that droplet spraying is a promising way to protect magnesium by using corrosion-resistant materials available now.

Using the latest reported homologous Chemokine receptors (PDB ID: 3ODU, 3OE0 and 3OE6) as templates, twenty models of angiotensin II (Ang II) type 1 (AT1) receptor (known as p30556) were generated by multiple templates homology modeling. According to the results of the initial validation of these twenty models, the model 0020 was finally chosen as the best one for further studies. Then, a 2 ns molecular dynamic (MD) simulation for model 0020 was conducted in normal saline (0.9%, w/V) under periodical boundary conditions, which was followed by docking studies of model 0020 with several existing AT1 receptor blockers (ARBs). The docking results reveal that model 0020 possesses good affinities with these docked ARBs which are in accordance with both the IC50 inhibitor values and their curative effects. The results also show more potent interactions between the model 0020 and its ARBs than those of ever reported results, such as hydrogen bonds, hydrophobic interactions, and especially cation-π interactions and π-π interactions which have never been reported before. This may reveal that the structure of the model 0020 is quite close to its real crystal structure and the model 0020 may have the potential to be used for structure based drug design.

A rapid and sensitive fluorometric method for the enzymatic detection of ethanol using CdSe/ZnS quantum dots (QDs) is proposed. The photoluminescence of QDs is sensitive to H₂O₂. This finding leads to a novel approach for the determination of ethanol using alcohol oxidase (AO_x) which, on oxidation of ethanol, produces H₂O₂. The method has higher sensitivity, wider analytical range (0.1–8 mmol/L), and a lower detection limit (0.05 mmol/L). The relationship between quenching of the photoluminescence of the QDs and the concentration of ethanol is linear.

A simple optimized microplate-based method to assay endo-1,4-β-mannosidase activity was described as an improved high-throughput screening method. A series of experimental conditions were optimized. It is revealed that the optimum measurement procedure is as follows: adding 50 μL of diluted enzyme sample and 50 μL substrate, incubating at 45 °C for exactly 5 min in micro-plate, mixing with 100 μL 3,5-dinitrosalicylic acid (DNS) reagent, maintaining at boiling point for 15 min, cooling down to room temperature before determining the ABS value at 540 nm using an ELISA micro-plate reader. The reaction volume of the optimized microplate-assay is reduced to 200 μL from 2 500 μL used in the standard β-mannanase macro-assay. The optimized micro-assay is significantly more sensitive in all of the 643 candidates during endo-1,4-β-mannosidase screening. Statistical analyses show that the sensitivity of the optimized micro-method is significantly greater than that of the macro-assay. The optimized method is convenient, fast, and cheap for high throughput enzyme screening.

Our previously described environmental DNA extraction method has been widely used in environmental microbial community analysis. However, residual humic substances may remain with obtained environmental DNA, which interferes downstream molecular analyses. To remedy this situation, two DNA extraction buffers (PIPES and Tris-HCl) and four purification strategies including our new modified low melting point gel purification method and three commercial kits from QIAEX, Omega and Promega were evaluated with diverse soil samples. The PIPES buffer (pH 6.5) is found to be more effective for removing the humic substances, but it leads to lower DNA yield and causes more severe DNA shearing than using the Tris-HCl buffer (pH 8.0). Gel purification and the Promega purification kit achieve much higher DNA recoveries than QIAEX or Omega kit, and higher purity of DNA is obtained by gel purification than by the Promega kit with both DNA extraction buffers mentioned above. Considering all results together, two alternative methods for DNA extraction and purification are proposed: one uses Tris-HCl buffer extraction and gel purification as the primary approach when the amount of soil or biomass is not a major concern, and the other uses PIPES buffer extraction and the Promega kit purification when severe DNA shearing and/or limited biomass occurs. Purified DNA samples by both methods are amenable for use as templates for whole community genome amplifications and PCR amplifications of bacterial 16S rRNA genes. It is demonstrated that these two alternative methods could be applied to a wide variety of environmental samples.

Laser assisted turning (LAT) is one of the advanced machining technologies, which uses laser power to heat the surface of a workpiece before the material is removed. It has several advantages of low manufacturing costs, high productivity and high qualities to machine difficult-to-cut materials such as silicon nitride, mullite, zirconia and Ni. A large part of studies on LAT have been focused on a round bar. With increasing demands for high quality products and high performance engineering system, the researches on LAT for clover and square section members are necessary. But, these workpieces are impossible to be machined on conventional CNC lathe and to generate NC code with current CAM softwares. As a basic research for combining LAT with a tilting index table type 5-axis machining center, i.e. laser assisted turn-mill, a new method is suggested to generate NC code that can process various types of clover and square section members through development of C++ program.

A multi-objective optimization model for draft scheduling of hot strip mill was presented, rolling power minimizing, rolling force ratio distribution and good strip shape as the objective functions. A multi-objective differential evolution algorithm based on decomposition (MODE/D). The two-objective and three-objective optimization experiments were performed respectively to demonstrate the optimal solutions of trade-off. The simulation results show that MODE/D can obtain a good Pareto-optimal front, which suggests a series of alternative solutions to draft scheduling. The extreme Pareto solutions are found feasible and the centres of the Pareto fronts give a good compromise. The conflict exists between each two ones of three objectives. The final optimal solution is selected from the Pareto-optimal front by the importance of objectives, and it can achieve a better performance in all objective dimensions than the empirical solutions. Finally, the practical application cases confirm the feasibility of the multi-objective approach, and the optimal solutions can gain a better rolling stability than the empirical solutions, and strip flatness decreases from (0±163) IU to (0±45) IU in industrial production.

For laser assisted machining, shape of preheating laser heat source is changed irregularly because of complexity of material shape. So, the preheating temperature should be controlled by adjusting the feed rate or the laser power. Thermal analyses of the laser assisted machining process for inclination planes were performed. By analyzing the obtained temperature profile, a proper feed rate control method was proposed according to the inclination angles. In addition, the temperature distribution of the cross section after feed rate control was predicted. The correlation equation between inclination angles and adjusted proper feed rate was proposed. The results of this analysis can be used to predict the preheating effect on workpiece and can be applied as a preheating temperature control method in laser assisted machining processes.

Autonomous underwater vehicles (AUVs) navigating on the sea surface are usually required to complete the communication tasks in complex sea conditions. The movement forms and flow field characteristics of a multi-moving state AUV navigating in head sea at high speed were studied. The mathematical model on longitudinal motion of the high-speed AUV in head sea was established with considering the hydrodynamic lift based on strip theory, which was solved to get the heave and pitch of the AUV by Gaussian elimination method. Based on this, computational fluid dynamics (CFD) method was used to establish the mathematical model of the unsteady viscous flow around the AUV with considering free surface effort by using the Reynolds-averaged Navier-Stokes (RANS) equations, shear-stress transport (SST) k-w model and volume of fluid (VOF) model. The three-dimensional numerical wave in the computational field was realized through defining the unsteady inlet boundary condition. The motion forms of the AUV navigating in head sea at high speed were carried out by the program source code of user-defined function (UDF) based on dynamic mesh. The hydrodynamic parameters of the AUV such as drag, lift, pitch torque, velocity, pressure, and wave profile were got, which reflect well the real ambient flow field of the AUV navigating in head sea at high speed. The computational wave profile agrees well with the experimental phenomenon of a wave-piercing surface vehicle. The force law of the AUV under the impacts of waves was analyzed qualitatively and quantitatively, which provides an effective theoretical guidance and technical support for the dynamics research and shape design of the AUV in real complex environment.

A lower-part humanoid robot CHP-1 with 12 degree-of-freedom of motion has been developed for cooperative motion, such as pushing or lifting an object. The capability of the robot is mainly dependent on the performance of the motors, thus the motors need to be properly selected. For the purpose, the kinematics of the robot was analyzed, and a number of simulations for two kinds of cooperative motions were carried out. The torques required at each motor of the robot under external forces were obtained. Here, the external forces were also estimated through simulation and literature survey. On the basis of the torques found, the selection of motors was finally suggested, and the motors are to be installed to the humanoid robot.

Many kinds of high temperature superconductor (HTS) power machines such as HTS cable, HTS fault current limiter and HTS magnet are cooled by liquid nitrogen. The level of liquid nitrogen should be monitored and controlled to ensure the thermal stability and the dielectric strength as well. To measure the level, capacitance method and differential pressure method are usually used. However, each method has installation difficulties and measurement errors for unsteady state operation with varying system pressure. A new liquid level meter using a 2G HTS conductor is described, which has similar structure with the liquid helium level meter with NbTi filament. The level meter is fabricated with a parallel connected heater, which helps the separation of the superconducting region and normal region, considering the critical temperature, large heat capacity of conductor and cooling characteristics. The level of liquid nitrogen can be obtained from the measured voltage signal along the 2G HTS conductor. Design, fabrication and test results of the new liquid nitrogen level meter are presented.

As dimensions of the metal-oxide-semiconductor field-effect transistor (MOSFET) are scaling down and the thickness of gate oxide is decreased, the gate leakage becomes more and more prominent and has been one of the most important limiting factors to MOSFET and circuits lifetime. Based on reliability theory and experiments, the direct tunneling current in lightly-doped drain (LDD) NMOSFET with 1.4 nm gate oxide fabricated by 90 nm complementary metal oxide semiconductor (CMOS) process was studied in depth. High-precision semiconductor parameter analyzer was used to conduct the tests. Law of variation of the direct tunneling (DT) current with channel length, channel width, measuring voltage, drain bias and reverse substrate bias was revealed. The results show that the change of the DT current obeys index law; there is a linear relationship between gate current and channel dimension; drain bias and substrate bias can reduce the gate current.

The natural frequency of the electrohydraulic system in mobile machinery is always very low, which brings difficulties to the controller design. To improve the tracking performance of the hydraulic system, mathematical modeling of the electrohydraulic lifting system and the rubber hose was accomplished according to an electrohydraulic lifting test rig built in the laboratory. Then, valve compensation strategy, including spool opening compensation (SOC) and dead zone compensation (DZC), was designed based on the flow-pressure characteristic of a closed-centered proportional valve. Comparative experiments on point-to-point trajectory tracking between a proportional controller with the proposed compensations and a traditional PI controller were conducted. Experiment results show that the maximal absolute values of the tracking error are reduced from 0.039 m to 0.019 m for the slow point-to-point motion trajectory and from 0.085 m to 0.054 m for the fast point-to-point motion trajectory with the proposed compensations. Moreover, tracking error of the proposed controller was analyzed and corresponding suggestions to reduce the tracking error were put forward.

A new efficient adapting virtual intermediate instruction set, V-IIS, is designed and implemented towards the optimized dynamic binary translator (DBT) system. With the help of this powerful but previously little-studied component, DBTs can not only get rid of the dependence of machine(s), but also get better performance. From our systematical study and evaluation, experimental results demonstrate that if V-IIS is well designed, without affecting the other optimizing measures, this could make DBT’s performance close to those who do not have intermediate instructions. This study is an important step towards the grand goal of high performance “multi-source” and “multi-target” dynamic binary translation.

Integrated with an improved architectural vulnerability factor (AVF) computing model, a new architectural level soft error reliability analysis framework, SS-SERA (soft error reliability analysis based on SimpleScalar), was developed. SS-SERA was used to estimate the AVFs for various on-chip structures accurately. Experimental results show that the AVFs of issue queue (IQ), register update units (RUU), load store queue (LSQ) and functional unit (FU) are 38.11%, 22.17%, 23.05% and 24.43%, respectively. For address-based structures, i.e., level1 data cache (L1D), DTLB, level2 unified cache (L2U), level1 instruction cache (L1I) and ITLB, AVFs of their data arrays are 22.86%, 27.57%, 14.80%, 8.25% and 12.58%, lower than their tag arrays’ AVFs which are 30.01%, 28.89%, 17.69%, 10.26% and 13.84%, respectively. Furthermore, using the AVF values obtained with SS-SERA, a qualitative and quantitative analysis of the AVF variation and predictability was performed for the structures studied. Experimental results show that the AVF exhibits significant variations across different structures and workloads, and is influenced by multiple microarchitectural metrics and their interactions. Besides, AVFs of SPEC2K floating point programs exhibit better predictability than SPEC2K integer programs.

In sensor networks, the adversaries can inject false data reports from compromised nodes. Previous approaches to filter false reports, e.g., SEF, only verify the correctness of the message authentication code (MACs) carried in each data report on intermediate nodes, thus cannot filter out fake reports that are forged in a collaborative manner by a group of compromised nodes, even if these compromised nodes distribute in different geographical areas. Furthermore, if the adversary obtains keys from enough (e.g., more than t in SEF) distinct key partitions, it then can successfully forge a data report without being detected en-route. A neighbor information based false report filtering scheme (NFFS) in wireless sensor networks was presented. In NFFS, each node distributes its neighbor information to some other nodes after deployment. When a report is generated for an observed event, it must carry the IDs and the MACs from t detecting nodes. Each forwarding node checks not only the correctness of the MACs carried in the report, but also the legitimacy of the relative position of these detecting nodes. Analysis and simulation results demonstrate that NFFS can resist collaborative false data injection attacks efficiently, and thus can tolerate much more compromised nodes than existing schemes.

A novel immune-swarm intelligence (ISI) based algorithm for solving the deterministic coverage problems of wireless sensor networks was presented. It makes full use of information sharing and retains diversity from the principle of particle swarm optimization (PSO) and artificial immune system (AIS). The algorithm was analyzed in detail and proper swarm size, evolving generations, gene-exchange individual order, and gene-exchange proportion in molecule were obtained for better algorithm performances. According to the test results, the appropriate parameters are about 50 swarm individuals, over 3 000 evolving generations, 20%–25% gene-exchange proportion in molecule with gene-exchange taking place between better fitness affinity individuals. The algorithm is practical and effective in maximizing the coverage probability with given number of sensors and minimizing sensor numbers with required coverage probability in sensor placement. It can reach a better result quickly, especially with the proper calculation parameters.

A method was proposed to evaluate the real-time reliability for a single product based on damaged measurement degradation data. Most researches on degradation analysis often assumed that the measurement process did not have any impact on the product’s performance. However, in some cases, the measurement process may exert extra stress on products being measured. To obtain trustful results in such a situation, a new degradation model was derived. Then, by fusing the prior information of product and its own on-line degradation data, the real-time reliability was evaluated on the basis of Bayesian formula. To make the proposed method more practical, a procedure based on expectation maximization (EM) algorithm was presented to estimate the unknown parameters. Finally, the performance of the proposed method was illustrated by a simulation study. The results show that ignoring the influence of the damaged measurement process can lead to biased evaluation results, if the damaged measurement process is involved.

Mission planning was thoroughly studied in the areas of multiple intelligent agent systems, such as multiple unmanned air vehicles, and multiple processor systems. However, it still faces challenges due to the system complexity, the execution order constraints, and the dynamic environment uncertainty. To address it, a coordinated dynamic mission planning scheme is proposed utilizing the method of the weighted AND/OR tree and the AOE-Network. In the scheme, the mission is decomposed into a time-constraint weighted AND/OR tree, which is converted into an AOE-Network for mission planning. Then, a dynamic planning algorithm is designed which uses task subcontracting and dynamic re-decomposition to coordinate conflicts. The scheme can reduce the task complexity and its execution time by implementing real-time dynamic re-planning. The simulation proves the effectiveness of this approach.

Energy-efficient data gathering in multi-hop wireless sensor networks was studied, considering that different node produces different amounts of data in realistic environments. A novel dominating set based clustering protocol (DSCP) was proposed to solve the data gathering problem in this scenario. In DSCP, a node evaluates the potential lifetime of the network (from its local point of view) assuming that it acts as the cluster head, and claims to be a tentative cluster head if it maximizes the potential lifetime. When evaluating the potential lifetime of the network, a node considers not only its remaining energy, but also other factors including its traffic load, the number of its neighbors, and the traffic loads of its neighbors. A tentative cluster head becomes a final cluster head with a probability inversely proportional to the number of tentative cluster heads that cover its neighbors. The protocol can terminate in O(n/lg n) steps, and its total message complexity is O(n²/lg n). Simulation results show that DSCP can effectively prolong the lifetime of the network in multi-hop networks with unbalanced traffic load. Compared with EECT, the network lifetime is prolonged by 56.6% in average.

The resistance loss of transportation was studied and the influences of buoyancy layout, mineral content and elastic modulus of flexible hose were investigated based on three-dimensional finite element model of fluid-solid interaction by MSC.MARC/MENTAT software. The numerical results show that the resistance losses increase with the increase of mineral content C_v and velocity of internal fluid v and decrease with the increase of elastic modulus E of flexible hose. The buoyancy layout and the velocity of internal fluid have greater impacts on the resistance losses than the elastic modulus of flexible hose. In order to reduce the resistance losses and improve the efficiency of the deep-ocean mining, C_v and v must be restricted in a suitable range (e.g. 10%–25% and 2.5–4 m/s). Effective buoyancy layout (such as Scheme C and D) should be adopted and the suitable material of moderate E should be used for the flexible hose in deep-ocean mining.

In order to explain the oscillation heat transfer dynamics of closed loop oscillation heat pipe (CLOHP) with two liquid slugs, analysis on the forces and heat transfer process of the partial gas-liquid phase system involving multiple parameters was carried out, and a new type oscillation heat transfer dynamic model of the CLOHP was set up based on conservation laws of mass, momentum and energy. Application results indicate that its oscillation heat transfer dynamics features depend largely on the filling rate, pipe diameter and difference in temperature. Besides, oscillation intensity and transfer performance can be improved to a large extent by increasing the temperature difference properly and enlarging the pipe diameter within a certain range under a certain filling rate.

Thermal performance is the most important factor in the development of a borehole heat exchanger utilizing geothermal energy. The thermal performance is affected by many different design parameters and different operating conditions such as bleeding. This eventually determines the operation and cost efficiency of the borehole heat exchanger system. The thermal performance of an open standing column well (SCW) type geothermal heat exchanger was assessed under the influence of bleeding. For this, a thermal response test rig was established with line-source theory. The test rig also had a bleeding function by releasing fluid while taking additional underground water through the heat exchanger. The thermal response test was performed with an additional constant input heat source. Effective thermal conductivity and thermal resistance were obtained from the measured data. From the measurement, the effective thermal conductivity is found to have 1.47 times higher value when bleeding is applied. The thermal resistance also increases by 1.58 times compared to a non-bleeding case. This trend indicates enhanced heat transfer in the SCW type heat exchanger with a bleeding function. Bleeding, therefore, could be an effective method of achieving a high heat transfer rate in the SCW type heat exchanger with sufficient underground water supply.

Flow distribution in branch piping system is affected by flow characteristics and different geometric variations. Most of the flow distribution studies are performed with one-dimensional analysis to yield overall information only. However, detailed analysis is required to find effects of design parameters on the flow distribution. For this aspect, three-dimensional turbulent flow analysis was performed to assess turbulence model performance and effects of upstream pressure and branch pipe geometry. Three different turbulence models of standard k-ɛ model, realizable k-ɛ model and standard k-ω yield similar results, indicating small effects of turbulence models on flow characteristics analysis. Geometric variations include area ratio of main and branch pipes, branch pipe diameter, and connection shape of main and branch pipes. Among these parameters, area ratio and branch diameter and shape show strong effect on flow distribution due to high friction and minor loss. Uniform flow distribution is one of common requirements in the branch piping system and this can be achieved with rather high total loss design.

A knowledge-based network for Section Yidong Bridge, Dongyang River, one tributary of Qiantang River, Zhejiang Province, China, is established in order to model water quality in areas under small data. Then, based on normal transformation of variables with routine monitoring data and normal assumption of variables without routine monitoring data, a conditional linear Gaussian Bayesian network is constructed. A “two-constraint selection” procedure is proposed to estimate potential parameter values under small data. Among all potential parameter values, the ones that are most probable are selected as the “representatives”. Finally, the risks of pollutant concentration exceeding national water quality standards are calculated and pollution reduction decisions for decision-making reference are proposed. The final results show that conditional linear Gaussian Bayesian network and “two-constraint selection” procedure are very useful in evaluating risks when there is limited data and can help managers to make sound decisions under small data.

Analyses of the effects of some parameters were performed to determine the admittance functions in a common two-compartment building with background porosity by the imposed excitation method. Variations of the magnification factors of fluctuating internal pressures were analyzed using 96 model cases under random fluctuating external pressure, and then corresponding design equations were fitted. The results show that the Helmholtz resonance peaks of the admittance functions in both compartments increase with increasing the area of windward or partition wall opening. With increasing the volume of the compartment with an external opening, the resonance peak in this compartment at the higher Helmholtz frequency significantly decreases, at the same time, the resonance peak in the other compartment at the lower Helmholtz frequency also decreases. With increasing the volume of the compartment with background porosity, both resonance peaks in this compartment at the lower and higher Helmholtz frequencies decrease, meanwhile, the resonance peak at the lower Helmholtz frequency for the other compartment also decreases, whereas the resonance peak at the higher Helmholtz frequency increases. Both resonance peaks of the admittance functions in the two compartments decrease with increasing the amplitude of fluctuating external pressure coefficients or reference wind speed.

A new double-yield-surface (DYS) model was developed to characterize the strength and deformation behaviors of coarse granular materials (CGMs). Two kinds of deformation mechanisms, including the shear and compressive plastic deformation, were taken into account in this model. These two deformation mechanisms were described by the shear and compressive yield functions, respectively. The Lode angle dependent formulations of proposed model were deduced by incorporating a 3D nonlinear unified failure criterion. Some comparisons were presented between the numerical predictions of proposed model and test data of true triaxial tests on the modeled rockfills. The model predictions are in good agreement with the test data and capture the strain hardening and plastic volumetric dilation of CGMs. These findings verify the reasonability of current DYS model, and indicate that this model is well suited to reproduce the stress-strain-volume change behavior of CGMs in general.

Risk quantification in grade is critical for mine design and planning. Grade uncertainty is assessed using multiple grade realizations, from geostatistical conditional simulations, which are effective to evaluate local or global uncertainty by honouring spatial correlation structures. The sequential Gaussian conditional simulation was used to assess uncertainty of grade estimates and illustrate simulated models in Sivas gold deposit, Turkey. In situ variability and risk quantification of the gold grade were assessed by probabilistic approach based on the sequential Gaussian simulations to yield a series of conditional maps characterized by equally probable spatial distribution of the gold grade for the study area. The simulation results were validated by a number of tests such as descriptive statistics, histogram, variogram and contour map reproductions. The case study demonstrates the efficiency of the method in assessing risk associated with geological and engineering variable such as the gold grade variability and distribution. The simulated models can be incorporated into exploration, exploitation and scheduling of the gold deposit.

Based on the height of back-filled materials, thickness of ore body, height of boundary pillar and dipping angle of ore body and water pressure, the safety factors of all the pillars are calculated with the limit equilibrium method. The calculation results present that the safety factors of pillars in Sections 19, 20, 24, 28 are less than 1.3, and those of unstable sections are identified preliminarily. Further, a numerical investigation in Sections 18, 20, 22, 24, 25 and 28 implemented with numerical code RFPA2D is employed to further validate the pillar performance and the stability of stopes. The numerical results show the pillars in Sections 18, 22 and 24 are stable and the designed pillar size is suitable. The width of the ore body near Section 28 averages 20 m, failure occurs in the left stope, but the boundary pillars near Section 28 maintain good performance. The pillars in Sections 20 and 25 are unstable which are mainly affected by the Faults F8 and F18. The existence of faults alters the stress distribution, failure mode and water inrush pathway. This work provides a meaningful standard for boundary pillar and stope design in a mine as it transitions from an open pit to underground.

A fast explicit finite difference method (FEFDM), derived from the differential equations of one-dimensional steady pipe flow, was presented for calculation of wellhead injection pressure. Recalculation with a traditional numerical method of the same equations corroborates well the reliability and rate of FEFDM. Moreover, a flow rate estimate method was developed for the project whose injection rate has not been clearly determined. A wellhead pressure regime determined by this method was successfully applied to the trial injection operations in Shihezi formation of Shenhua CCS Project, which is a good practice verification of FEFDM. At last, this method was used to evaluate the effect of friction and acceleration terms on the flow equation on the wellhead pressure. The result shows that for deep wellbore, the friction term can be omitted when flow rate is low and in a wide range of velocity the acceleration term can always be deleted. It is also shown that with flow rate increasing, the friction term can no longer be neglected.

The cracking patterns of a thin sheet with a pre-existing crack subjected to dynamic loading are numerically simulated to investigate the mechanism of crack branching by using the FEM method. Six numerical models were set up to study the effects of load, tensile strength and heterogeneity on crack branching. The crack propagation is affected by the applied loads, tensile strength and heterogeneity. Before crack branching, the crack propagates by some distance along the direction of the pre-existing crack. For the materials with low heterogeneity, the higher the applied stress level is and the lower the tensile strength of the material is, the shorter the propagation distance is. Moreover, the branching angle becomes larger and the number of branching cracks increases. In the case of the materials with high heterogeneity, a lot of disordered voids and microcracks randomly occur along the main crack, so the former law is not obvious. The numerical results not only are in good agreement with the experimental observations in laboratory, but also can be extended to heterogeneity media. The work can provide a good approach to model the cracking and fracturing of heterogeneous quasi-brittle materials, such as rock, under dynamic loading.

A numerical code called RFPA-Dynamics was used to study the rockburst mechanism under dynamic load based on coupled static-dynamic analysis. The results show that dynamic disturbance has a very distinct triggering effect on rockburst. Under the dynamic load, rockburst is motivated by tensile stress formed by the overlapping of dynamic waves in the form of instantaneous open and cutting through of cracks in weak planes and pre-damaged areas. Meanwhile, the orientation of joint sets has an obvious leading effect on rockburst locations. Finally, a higher initial static stress state before dynamic loading can cause more pre-damaged area, thus leading to a larger rockburst scope.

Based on the analysis of several objective functions, a new method was proposed. Firstly, the feature of the inclination curve was analyzed. On this basis, the soil could be divided into several blocks with different displacements and deformations. Then, the method of the soil division was presented, and the characteristic of single soil block was studied. The displacement of the block had two components: sliding and deformation. Moreover, a new objective function was constructed according to the deformation of the soil block. Finally, the sensitivities of the objective functions by traditional method and the new method were calculated, respectively. The result shows that the new objective function is more sensitive to mechanical parameters and the inversion result is close to that obtained by the large direct shear apparatus. So, this method can be used in slope back analysis and its effectiveness is proved.

A formula was derived for the computation of seismic active earth pressure behind retaining wall using pseudo-dynamic method. This formula considered the actual dynamic effect with variation of time and propagation of shear and primary wave velocities through the soil backfills. The influence of tension crack in the top portion of the backfill under seismic loading was investigated. The effects of wall friction angle, soil friction angle, horizontal and vertical seismic coefficients on the seismic active force were also explored. The parametric study shows that the total seismic active force increases as horizontal seismic coefficient increases, while it decreases with the increase in vertical seismic coefficient, internal friction angle and unit cohesion. The seismic active force calculated by the proposed method is larger than that calculated by previous theory.

The long-term stability of large-span soft rock tunnel is influenced greatly by the creep effect of surrounding rock. The development of a new type of foam concrete which has the property of high compressibility and low ductility was introduced. And it was made as filling material of reserved deformation layer between the first lining and the second lining used in large-span soft rock tunnel. The effect of the new type of foam concrete was simulated as filling material of reserved deformation layer using numerical simulation. Through the comparison with the common large-span soft rock tunnel, the vault settlement and surrounding convergence are reduced by about 61% and 45%, respectively, after creep of 100 a. And in the second lining, the plastic zone reduces apparently and the maximum equivalent plastic strain decreases relatively. So, it can be found that the application of the new type of foam concrete as the filling material of reserved deformation layer can relieve the excessive force in second lining induced by rock creep, reduce its deformation and improve the stability of tunnel.

A new method integrating support vector machine (SVM), particle swarm optimization (PSO) and chaotic mapping (CPSO-SVM) was proposed to predict the deformation of tunnel surrounding rock mass. Since chaotic mapping was featured by certainty, ergodicity and stochastic property, it was employed to improve the convergence rate and resulting precision of PSO. The chaotic PSO was adopted in the optimization of the appropriate SVM parameters, such as kernel function and training parameters, improving substantially the generalization ability of SVM. And finally, the integrating method was applied to predict the convergence deformation of the Xiakeng tunnel in China. The results indicate that the proposed method can describe the relationship of deformation time series well and is proved to be more efficient.

Deformation characteristics of light weight soil with different EPS (expanded polystyrene) sizes were investigated by consolidation tests. The results show that the confined stress-strain relation curve is in S shape, which has a good homologous relation with e-p curve and e-lgp curve, and three types of curves reflect obvious structural characteristics of light weight soil. When cement mixed ratio and EPS volume ratio are the same for different specimens, structural strength decreases with the increase of EPS size, but compressibility indexes basically keep unchanged within the structural strength. The settlement of light weight soil can be divided into instantaneous settlement and primary consolidation settlement. It has no obvious rheology property, and 90% of total consolidation deformation can be finished in 1 min. Settlement-time relation of light weight soil can be predicted by the hyperbolic model. S-lgt curve of light weight soil is not in anti-S shape. It is proved that there is no secondary consolidation section, so consolidation coefficient cannot be obtained by time logarithm method. Structural strength and unit price decrease with the increase of EPS size, but the reducing rate of the structural strength is lower than that of the unit price, so the cost of mixed soil can be reduced by increasing the EPS size. The EPS beads with 3–5 mm in diameter are suggested to be used in the construction process, and the prescription of mixed soil can be optimized.

Compressive and flexural strength, fracture energy, as well as fatigue property of pervious cement concrete with either supplementary cementitious materials (SCMs) or polymer intensified, were analyzed. Test results show that the strength development of SCM-modified pervious concrete (SPC) differs from that of polymer-intensified pervious concrete (PPC), and porosity has little effect on their strength growth. PPC has higher flexural strength and remarkably higher flexural-to-compressive strength ratio than SPC at the same porosity level. Results from fracture test of pervious concrete mixes with porosity around 19.5% show that the fracture energy increases with increasing the dosage of polymer, reflecting the ductile damage features rather than brittleness. PPC displays far longer fatigue life than SPC for any given failure probability and at any stress level. It is proved that two-parameter Weibull probability function describes the flexural fatigue of pervious concrete.

Crack is found to be a major distress that affects the performance of the epoxy asphalt pavement. An extended finite element method was proposed for investigating the fracture properties of the epoxy asphalt mixture. Firstly, the single-edge notched beam test was used to analyze the temperature effect and calculate the material parameters. Then, the mechanical responses were studied using numerical analysis. It is concluded that 5 °C can be selected as the critical temperature that affects the fracture properties, and numerical simulations indicate that crack propagation is found to significantly affect the stress state of the epoxy asphalt mixture. The maximum principal stress at the crack surface exhibits different trends at various temperatures. Numerical solution of stress intensity factor can well meet the theoretical solution, especially when the temperature is lower than 5 °C.

In order to solve the failure of fuel system when using petroleum coke oil slurry (PCOS) in a R180 diesel engine directly, a petroleum coke oil slurry fuel system (PCOSFS) was developed and installed in R180 engine, which was called PCOS engine. In order to analyze performances and emissions of the PCOS engine, a comparative experiment between PCOS engine fueled with PCOS and R180 engine fueled with diesel oil was carried out. The results show that the PCOS engine can run smoothly, the maximum output power decreases by about 6.2% and 19.0% and the maximum brake thermal efficiency reduces by around 5.85% and 4.13% as compared to R180 engine under the conditions of 1 200 and 1 600 r/min. The HC emissions of PCOS engine are lower than those of R180 engine at 1 200 r/min, and are close to those of R180 engine at 1 600 r/min. The CO emissions are similar to R180 engine at 1 200 and 1 600 r/min. The smoke intensity is close to R180 engine at 1 200 r/min, and is higher than R180 engine at 1 600 r/min. The particles emitted from PCOS engine array sparsely, but particles emitted from R180 engine array closely, cohering together.

Pedestrian’s road-crossing model is the key part of micro-simulation for mixed traffic at signalized intersection. To reproduce the crossing behavior of pedestrians, the microscopic behaviors of the pedestrians passing through the crosswalk at signalized intersection were analyzed. A pedestrian’s decision making model based on gap acceptance theory was proposed. Based on the field data at three typical intersections in Beijing, China, the critical gaps and lags of pedestrians were calibrated. In addition, considering pedestrian’s required space, a modification of the social force model that consists of a self-deceleration mechanism prevents a simulated pedestrian from continuously pushing over other pedestrians, making the simulation more realistic. After the simple change, the modified social force model is able to reproduce the fundamental diagram of pedestrian flows for densities less than 3.5 m⁻² as reported in the literature.