The microstructure evolutions of two Al-Zn-Mg alloys, one of which was alloyed with Sc and Zr, and the kinetics of Al3(Sc1−xZrx) precipitates in the Al-Zn-Mg alloy during homogenization were investigated. Both alloys under as-cast condition with supersaturated, non-equilibrium T(Mg32(Al, Zn)49) phase and impurities phase were displayed. When the homogenization temperatures are below 350 °C, Zn and Mg atoms precipitate from matrix; however, when the temperatures are above 400 °C, T phase dissolves into matrix, enhancing solid-solution strengthening. Kinetics of Al3(Sc1−xZrx) precipitates was studied based on Jmat Pro software calculation and the difference values between the hardness of the two alloys in each homogenization condition. The calculations predict that the Sc and Zr solubilities in α-Al decline with the presence of Mg and Zn. Investigation of the difference values reveals that when the temperature is between 300 °C and 350 °C, the nucleation rate of Al3(Sc1−xZrx) precipitates is the highest and the strengthening effect from Al3(Sc1−xZrx) precipitates is the best. After homogenization at 470 °C for 12 h, non-equilibrium T phase disappears, while impurity phase remains. The mean diameter of Al3(Sc1−xZrx) precipitates is around 18 nm. Ideas about better fulfilling the potentials of Sc and Zr were proposed at last.
A novel chemical liquid reduction process was employed to prepare nanosized Mo-Cu powders. The precipitates were first obtained by adding ammonium heptamolybdate ((NH4)6Mo7O24·4H2O) solution into excess hydrazine hydrate solution, and then mixed the copper chloride solution. The precipitates were subsequently washed, dried, followed by reducing in H2 atmosphere to convert into Mo-Cu composite powders. The composition, morphology and particle size of the Mo-Cu composite powders were characterized by the XRD, SEM and TEM. The effects of the chemical reaction temperature and the magnetic stirring on the morphology of the Mo-Cu powders were also studied. The results show that Mo-Cu powders produced by the chemical liquid reduction process are nearly spherical shape and dispersive distribution state, with particle size ranging from 50 to 100 nm. The chemical reaction temperature and magnetic stirring will change the particle feature of the powders. Because of the Cu3Mo2O9, the reduction process in H2 is the one-stage reduction from the precipitates to the Mo-Cu composite powders.
Infrared emissivity was studied in Zn0.99M0.01O (M is Mn, Fe or Ni) and Zn1−xCoxO (x=0.01, 0.02, 0.03 and 0.04) powders synthesized by solid-state reaction at various temperatures. XRD patterns confirm the wurtzite structure of the prepared samples. No peaks of other phases arising from impurities are detected in Mn- and Co-doped ZnO, but the peaks of ZnFe2O4 and NiO are observed in Zn0.99Fe0.01O and Zn0.99Ni0.01O. The SEM observations indicate that with larger grain sizes than those of Zn0.99Fe0.01O and Zn0.99Ni0.01O, Co-doped ZnO exhibits smooth grain surfaces. The infrared absorption spectra show that infrared absorptions related to oxygen in Zn0.99M0.01O are much stronger than those in Co-doped ZnO. Co ions are dissolved into the ZnO lattice with Co2+ state from XPS spectra analysis. The infrared emissivity results imply that the emissivity of Zn0.99Ni0.01O is the highest (0.829) and that of Zn0.99Co0.01O is the lowest (0.784) at 1 200 °C. The emissivity of Zn0.99Co0.01O decreases to the minimum (0.752) at 1 150 °C and then increases with growing calcination temperature. As the Co doping content grows, the emissivity of Co-doped ZnO calcined at 1 200 °C falls to 0.758 in the molar fraction of 3% and then ascends.
Combining the optimization and FEM technology, crashworthiness of aluminum extrusions was studied for an automobile safety plan. The effects of longitudinal stiffeners on the crushing of stiffened square columns were studied considering the damage evolution. The numerical analysis was carried out by ABAQUS software. Subsequently, the collapse behavior of aluminum extrusion damage was validated by comparing against solution published in literature. Finally, in order to find more efficient and lighter crush absorber and achieving minimum peak crushing force, response surface methodology (RSM) has been applied for optimizing the aluminum extrusion tube.
Polydimethylsiloxane (PDMS), tetraethoxysilane (TEOS), ethyl alcohol (EtOH) and deionized water were main raw materials to prepare silicone-modified hybrid thin films using sol-gel method. The effect of the contents of H2O and PDMS on thin films was studied. When the volume ratio of H2O to TEOS is 0.5, the optimum quality of thin films is obtained. And the gelation time is affected slightly by H2O content. Uniform thin films are obtained when the volume ratio of PDMS to TEOS is 0.2. Yet, the sol would be inactive in 6 d. Various properties of thin films were studied, including hardness, adhesive quality, hydrophobic property, corrosion protection property, and abrasion resistance. Test results show that the pencil hardness is generally 3–6 H, and adhesive quality achieves the highest standard of 0. When the sintering temperature is below 400 °C, the contact angle is about 95° and hydrophobic films are obtained. The abrasion resistance of thin films is better than that of aluminum alloy when the sintering temperature is higher than 300 °C. And the excellent corrosion protective effect is obtained by single-layer coating when the sintering temperature is higher than 400 °C.
The feasibility of separation of lead anode slime with low silver by vacuum distillation was analyzed theoretically. The volatilization rates and mass fractions of elements, influenced by distillation temperature, heat preservation time and material thickness, were investigated under laboratory conditions. The experimental results indicate that almost all of lead and bismuth can be separated from silver-contained multicomponent alloy at 1 223 K for 45 min when the chamber pressure maintains at 10–25 Pa. Silver can be easily enriched in the residue and its mass fraction increases from 3.6% to 27.8% when the distillation temperature is between 1 133 K and 1 373 K. Due to the forming of intermetallic compounds Cu2Sb, Cu10Sb3 and Ag3Sb, the antimony could not be evaporated completely during the vacuum distillation. EDS analysis indicates that the condensate has a columnar crystal structure.
Some effective parameters on the copper extraction from Küre chalcopyrite concentrate were optimized by using response surface methodology (RSM). Experiments designed by RSM were carried out in the presence of ammonium persulfate (APS) and different types of impeller in an autoclave system. Ammonium persulfate concentration and leaching temperature were defined numerically and three types of impellers were defined categorically as independent variables using experimental design software. The optimum condition for copper extraction from the chalcopyrite concentrate is found to be ammonium persulfate concentration of 277.77 kg/m3, leaching temperature of 389.98 K and wheel type of impeller. The proposed model equation using RSM has shown good agreement with the experimental data, with correlation coefficients R2 and Radj2 for the model as 0.89 and 0.84, respectively.
Perfluorolyether is characterized by highly chemical inertness, oxidative stability, anticorrosion as well as radiation resistance. It can be used as lubricant especially in harsh environmental conditions. In this work, hexafluoropylene oxide was catalytically polymerized at low temperature using the methods of anionic polymerization, and perfluorolyethers were obtained with number-average degree of polymerization more than 15. CsF and RbF were used as catalysts and their catalytic activities were investigated. Experimental results show that perfluorolyethers with number-average molar masses up to 3 000 g/mol could be obtained using the two kinds of catalysts, respectively. As compared to CsF, the number-average degree of polymerization is higher and the relative molecular mass distribution interval is narrower when RbF is used as catalyst. The effect of factors such as impurities’ content, reaction temperature and reaction time on the number-average degree of polymerization was also investigated. It is found that low impurities’ content and low temperature are beneficial to the generation of high number-average degree of perfluorolyethers. The optimization reaction time is 24 h, and further increase of reaction time does not significantly affect the average relative molecular mass. The product was characterized by IR, 19F NMR and GC-MS, and the catalytic mechanism was analyzed finally.
The behavior of the active layer of material bed within rotary kilns plays a key role in industrial applications. To obtain its influences on industrial process, different regimes of particle motion have been simulated by discrete element method (DEM) in three dimensions under variant rotation speeds, filling degree, based on the background of induration process of iron ore pellets. The influences of the mentioned factors on the maximum thickness of the active layer and the average velocity of particles have been investigated. The average velocity of particles increases with Froude number following the power function over a wide range, and the maximum thickness rises with increasing rotation speed in a way of logarithm. The influence of the filling degree f on the maximum thickness exhibits a good linearity under two classic regimes, but the increasing of the average velocity of the active layer is limited at f=0.4. This basic research highlights the impact of the active layer within rotary kilns, and lays a good foundation for the further investigation in mixing and heat transfer within the particle bed inside rotary kilns.
The effect of static transmission error on nonlinear dynamic response of the spiral bevel gear system combining with time-varying stiffness and backlash was investigated. Firstly, two different control equations of the spiral bevel gear model were adopted, where the static transmission error was expressed in two patterns as predesigned parabolic function and sine function of transmission errors. The dynamic response, bifurcation map, time domain response, phase curve and Poincare map were obtained by applying the explicit Runge-Kutta integration routine with variable-step. A comparative study was carried out and some profound phenomena were detected. The results show that there are many different kinds of tooth rattling phenomena at low speed. With the increase of speed, the system enters into stable motion without any rattling in the region (0.72, 1.64), which indicates that the system with predesigned parabolic function of transmission error has preferable capability at high speed.
Based on the working principle and the damping characteristic of hydraulic shock absorber, a fluid structure interaction method was presented, which was used to analyze the microcosmic and high-frequency processing mechanism of fluid structure interaction between circulation valve and liquid of hydraulic shock absorber. The fluid mesh distortion was controlled by the CEL language, and the fluid structure interaction mathematical model was established. The finite element model was established by ANSYS CFX software and was analyzed by dynamic mesh technique. The local sensitive computational area was meshed by prismatic grid, which could reduce the negative volume problem during the simulation. The circulation valve and liquid of hydraulic shock absorber were simulated and analyzed under the condition of sinusoidal inlet velocity loads. Flow characteristic and dynamics characteristic were obtained. The pressure distribution and the displacement of circulation value were obtained, and the acceleration curve of circulation valve was simulated and analyzed. The conformity of the final simulation results with the experimental datum indicates that this method is accurate and reliable to analyze the dynamics characteristic between circulation valve and liquid of hydraulic shock absorber, which can provide a theoretical foundation for optimizing hydraulic shock absorber in the future.
A new approach of smoothing the white noise for nonlinear stochastic system was proposed. Through presenting the Gaussian approximation about the white noise posterior smoothing probability density function, an optimal and unifying white noise smoothing framework was firstly derived on the basis of the existing state smoother. The proposed framework was only formal in the sense that it rarely could be directly used in practice since the model nonlinearity resulted in the intractability and infeasibility of analytically computing the smoothing gain. For this reason, a suboptimal and practical white noise smoother, which is called the unscented white noise smoother (UWNS), was further developed by applying unscented transformation to numerically approximate the smoothing gain. Simulation results show the superior performance of the proposed UWNS approach as compared to the existing extended white noise smoother (EWNS) based on the first-order linearization.
To improve the performance of chaotic secure communication, three simplified chaotic systems with one variable parameter were investigated. Basic properties were analyzed including symmetry, dissipation and topological structure. Complex dynamical behaviors of the systems including chaos and periodic orbits were verified by numerical simulations, Lyapunov exponents and bifurcation diagrams. Interestingly, the three systems were integrated in a common circuit, and their dynamical behaviors were easily observed by adjusting regulable resistors R28, R14 and R17, respectively, and the relations between the variable resistor and the system parameter were deduced. The circuit experiment results agree well with the simulation results. Finally, a secure communication scheme based on chaos shift keying (CSK) was presented, which lays an experiment foundation for chaotic digital secure communication.
Aiming at the potential presence of mixing automatic identification system (AIS) signals, a new demodulation scheme was proposed for separating other interfering signals in satellite systems. The combined iterative cross-correlation demodulation scheme, referred to as CICCD, yielded a set of single short signals based on the prior information of AIS, after the frequency, code rate and modulation index were estimated. It demodulates the corresponding short codes according to the maximum peak of cross-correlation, which is simple and easy to implement. Numerical simulations show that the bit error rate of proposed algorithm improves by about 40% compared with existing ones, and about 3 dB beyond the standard AIS receiver. In addition, the proposed demodulation scheme shows the satisfying performance and engineering value in mixing AIS environment and can also perform well in low signal-to-noise conditions.
Many energy efficiency asynchronous duty-cycle MAC (media access control) protocols have been proposed in recent years. However, in these protocols, wireless sensor nodes almost choose their wakeup time randomly during the operational cycle, which results in the packet delivery latency increased significantly on the multiple hops path. To reduce the packet delivery latency on multi-hop path and energy waste of the sender’s idle listening, a new low latency routing-enhanced asynchronous duty-cycle MAC protocol was presented, called REA-MAC. In REA-MAC, each sensor node decided when it waked up to send the beacon based on cross-layer routing information. Furthermore, the sender adaptively waked up based on the relationship between the transmission request time and the wakeup time of its next hop node. The simulation results show that REA-MAC reduces delivery latency by 60% compared to RI-MAC and reduces 8.77% power consumption on average. Under heavy traffic, REA-MAC’s throughput is 1.48 times of RI-MAC’s.
To overcome the disadvantage that the standard least squares support vector regression (LS-SVR) algorithm is not suitable to multiple-input multiple-output (MIMO) system modelling directly, an improved LS-SVR algorithm which was defined as multi-output least squares support vector regression (MLSSVR) was put forward by adding samples’ absolute errors in objective function and applied to flatness intelligent control. To solve the poor-precision problem of the control scheme based on effective matrix in flatness control, the predictive control was introduced into the control system and the effective matrix-predictive flatness control method was proposed by combining the merits of the two methods. Simulation experiment was conducted on 900HC reversible cold roll. The performance of effective matrix method and the effective matrix-predictive control method were compared, and the results demonstrate the validity of the effective matrix-predictive control method.
A new ultrasound contrast imaging technique was proposed for eliminating the harmonic components from the emission signal transmitted by the broadband ultrasonic system. Reversal phase-inversion pulse was used for the first time to separate the contrast harmonics from the harmonics in the emission signal to improve the detection of contrast micro-bubbles. Based on the nonlinear acoustic theory of finite-amplitude effects and the associated distortion of the propagating wave, the Bessel-Fubini series model was applied to describe the nonlinear propagation effects of the reversal phase-inversion pulse, and the Church’s equation for zero-thickness encapsulation model was used to produce the scattering-pulse of the bubble. For harmonic imaging, the experiment was performed using a 64-element linear array, which was simulated by Field II. The results show that the harmonic components from the emission signal can be completely cancelled, and the harmonics generated by the nonlinear propagation of the wave through the tissue, can be reduced by 15–30 dB. Compared with the short pulse, the reversal phase-inversion pulse can improve the contrast and definition of the harmonic image significantly.
High resolution range imaging with correlation processing suffers from high sidelobe pedestal in random frequency-hopping wideband radar. After the factors which affect the sidelobe pedestal being analyzed, a compressed sensing based algorithm for high resolution range imaging and a new minimized l1-norm criterion for motion compensation are proposed. The random hopping of the transmitted carrier frequency is converted to restricted isometry property of the observing matrix. Then practical problems of imaging model solution and signal parameter design are resolved. Due to the particularity of the proposed algorithm, two new indicators of range profile, i.e., average signal to sidelobe ratio and local similarity, are defined. The chamber measured data are adopted to testify the validity of the proposed algorithm, and simulations are performed to analyze the precision of velocity measurement as well as the performance of motion compensation. The simulation results show that the proposed algorithm has such advantages as high precision velocity measurement, low sidelobe and short period imaging, which ensure robust imaging for moving targets when signal-to-noise ratio is above 10 dB.
A comparison of the effectiveness of installing reactive power compensators, such as shunt capacitors, static var compensators (SVCs), and static synchronous compensators (STATCOMs), was presented in large-scale power networks. A suitable bus was first identified using modal analysis method. The single shunt capacitor, single SVC, and single STATCOM were installed separately on the most critical bus. The effects of the installation of different devices on power loss reduction, voltage profile improvement, and voltage stability margin enhancement were examined and compared for 57- and 118-bus transmission systems. The comparative study results show that SVC, and STATCOM are expensive compared to shunt capacitor, yet the effect of installing STATCOM is better than SVC and the effect of installing SVC is better than that of shunt capacitor in achieving power loss reduction, voltage profile improvement and voltage stability margin enhancement.
To investigate the influence of bluff body shape on wall pressure distribution in a vortex flowmeter, experiments were conducted on a specially designed test section in a closed water rig at Reynolds numbers of 6.2×104-9.3×104. The cross sections of the bluff bodies were semicircular, square, and triangular shaped, and there were totally 21 pressure tappings along the conduit to acquire the wall pressures. It is found that the variation trends of wall pressures are basically identical regardless of the bluff body shapes. The wall pressures begin to diverge from 0.3D (D is the inner diameter of the vortex flowmeter) in front of the bluff body due to the diversity in shape, and all reach the minimum values at 0.3D behind the bluff body. A discrepancy between the triangular or square cylinder and the semicircular cylinder in wall pressure change is observed at 0–0.1D behind the bluff body. It is also found that the wall pressures and irrecoverable pressure loss coefficients increase with flow rates, and the triangular cylinder causes the smallest irrecoverable pressure loss at a fixed flow rate.
To study the abilities of Chlorella sorokiniana CS-01 on using CO2 from flue gases to produce biodiesel, the microaglae was cultured with different simulated flue gases containing 5%–15% (volume fraction) of CO2. The results show that strain CS-01 could grow at 15% CO2 and grow well under CO2 contents ranging from 5%–10%. The maximal biomass productivity and lipid productivity were obtained when aerating with 10% of CO2. The lipids content ranged from 28% to 43% of dry mass of biomass. The main fatty acid compositions of strain CS-01 were C14-C18 (>72%) short-chain FAMEs (known as biodiesel feedstocks). Meanwhile, the biodiesel productivity was over 60%, suggesting that Chlorella sorokiniana CS-01 has a great potential for CO2 mitigation and biodiesel production. Furthermore, differential expression of three genes related to CO2 fixation and fatty acid synthesis were studied to further describe the effect of simulated flue gases on the growth and lipid accumulation of strain CS-01 at molecular level.
Organic Rankine cycle (ORC) power plant operating with supercritical parameters supplied by low temperature slag-washing water (SWW) of blast furnace was investigated. A schematic of such installation was presented with a description of its operation and the algorithm of calculations of a supercritical power plant. Two typical organic fluids with sufficiently low critical parameters were selected as candidate working fluids in the plant to study the efficiency of the system with different organic fluids. An analysis of the influence on the effectiveness of operation of a plant was carried out. With the same temperature of slag-washing water, the specific work in turbine of fluid R143a is 45% higher than that obtained for the fluid R125, however, the specific work in pump of fluid R143a is approximate equal into that one of the fluid R125.
Copper smelting is a significant source of SO2 emission. It is important to quantify SO2 emissions from combustion sources for regulatory and control purposes in relation to air quality. The characteristics of SO2 emissions from copper smelting industry in Yunnan Province, China, were examined. Analysis based on the present situation, material balance and measuring method were used to confirm SO2 emission factors of copper smelting industry. Results show that SO2 emission factors for Isa system, side blown-continuous converting system (SB-CC), blast furnace-continuous converting systems (B-CC) and blast furnace-converter blowing (B-C) are 11.69–18.64, 62.44–101.4, 19.43–37.88 and 45.48–81.03 kg/t(blister copper), respectively. The comprehensive emission factor based on all smelting plants is found to be in the range of 23–39.99 kg-SO2/t(blister copper) for Yunnan Province, China. The results are compared with those for discharge coefficients of industrial pollutants in the First National General Survey of Pollution Sources and the emission factor of the total amount of major pollutants. It is observed that there are some differences among emission factors.
The relationship between Solidago canadensis L. invasion and soil microbial community diversity including functional and structure diversities was studied across the invasive gradients varying from 0 to 40%, 80%, and 100% coverage of Solidago canadensis L. using sole carbon source utilization profiles analyses, principle component analysis (PCA) and phospholipid fatty acids (PLFA) profiles analyses. The results show the characteristics of soil microbial community functional and structure diversity in invaded soils strongly changed by Solidago canadensis L. invasion. Solidago canadensis L. invasion tended to result in higher substrate richness, and functional diversity. As compared to the native and ecotones, average utilization of specific substrate guilds of soil microbe was the highest in Solidago canadensis L. monoculture. Soil microbial functional diversity in Solidago canadensis L. monoculture was distinctly separated from the native area and the ecotones. Aerobic bacteria, fungi and actinomycetes population significantly increased but anaerobic bacteria decreased in the soil with Solidago canadensis L. monoculture. The ratio of cy19:0 to 18:1ω7 gradually declined but mono/sat and fung/bact PLFAs increased when Solidago canadensis L. became more dominant. The microbial community composition clearly separated the native soil from the invaded soils by PCA analysis, especially 18:1ω7c, 16:1ω7t, 16:1ω5c and 18:2ω6, 9 were present in higher concentrations for exotic soil. In conclusion, Solidago canadensis L. invasion could create better soil conditions by improving soil microbial community structure and functional diversity, which in turn was more conducive to the growth of Solidago canadensis L.
A newly isolated bacterium was screened out for its survival on medium with 6 000 mg/L kraft lignin as the sole carbon source and energy, and identified as Pandoraea sp. by 16S rRNA gene sequence analysis. The biodegradation experiment was carried out in mineral salt medium, containing 5 000 mg/L kraft lignin as only carbon and energy at pH 8.0 and 30 °C. Under these conditions, significant reduction in color and lignin content by the strain was observed after incubation for 5 d. The strain attains maximum reduction capability in color (44.6%) and lignin content (39.9%) within 5 d of incubation, and reduced chemical oxygen demand(COD) from initial concentration 7 399 to 3 980 mg/L at maximum reduction level of 46.2% on the 4th day. The total ion chromatograph (TIC) of compounds presented in the chloroform extract of control and bacterial treated samples shows the formation of several lignin-related aromatic compounds including some small molecular lignin fragments, indicating a strong destruction in the lignin structure.
The absorbing boundary is the key in numerical simulation of borehole radar. Perfect match layer (PML) was chosen as the absorbing boundary in numerical simulation of GPR. But CPML (convolutional perfect match layer) approach that we have chosen has the advantage of being media independent. Beginning with the Maxwell equations in a two-dimensional structure, numerical formulas of finite-difference time-domain (FDTD) method with CPML boundary condition for transverse electric (TE) or transverse magnetic (TM) wave are presented in details. Also, there are three models for borehole-GPR simulation. By analyzing the simulation results, the features of targets in GPR are obtained, which can provide a better interpretation of real radar data. The results show that CPML is well suited for the simulation of borehole-GPR.
In order to accurately predict the productivity of herringbone multilateral well, a new productivity prediction model was founded. And based on this model, orthogonal test and multiple factor variance analysis were applied to study optimization design of herringbone multilateral well. According to the characteristics of herringbone multilateral well, by using pressure superposition and mirror image reflection theory, the coupled model of herringbone multilateral well was developed on the basis of a three-dimensional pseudo-pressure distribution model for horizontal wells. The model was formulated in consideration of friction loss, acceleration loss of the wellbore and mixed loss at the confluence of main wellbore and branched one. After mathematical simulation on productivity of the herringbone multilateral well with the coupled model, the effects of well configuration on productivity were analyzed. The results show that lateral number is the most important factor, length of main wellbore and length of branched wellbore are the secondary ones, angle between main and branched one has the least influence.
Twenty one joints were made with Brazilian tests and each surface was scanned by the Talysurf CLI 2000. Morphological characteristics of joint surface were quantified by statistical and textural parameters. By the contrast of these parameters between both sides of each coupled joint, the following conclusions are drawn. The upper and lower surfaces of coupled joints have approximately equal values of Sp(maximum height of joint surface), Sa(arithmetic mean height of joint surface) and Sq(root mean square height of joint surface), but the Ssk(skewness of the height distribution of joint surface) values of the two surfaces of a coupled joint are different, one is positive while the other is negative. The Sal(auto-correlation length) parameter values of both surfaces of each coupled joint are quite close, and the Str(texture aspect ratio) values have the same situation to the Sal parameter, but the same parameters of different surfaces have big differences which illustrates its own characteristics of each joint. The two surfaces of each coupled joint have similar values of (mean profile angle) which can be used to deduce the value of each other.
Ground improvement has been used on many construction sites to densify granular materials, in other word, to improve soil properties and reduce potential settlement. This work presents a case study of ground improvement using rapid impact compaction (RIC). The research site comprises the construction of workshop and depots as part of railway development project at Batu Gajah-Ipoh, Malaysia. In-situ testing results show that the subsurface soil comprises mainly of sand and silty sand through the investigated depth extended to 10 m. Groundwater is approximately 0.5 m below the ground surface. Evaluation of improvement was based on the results of pre- and post-improvement cone penetration test (CPT). Interpretation software has been used to infer soil properties. Load test was conducted to estimate soil settlement. It is found that the technique succeeds in improving soil properties namely the relative density increases from 45% to 70%, the friction angle of soil is increased by an average of 3°, and the soil settlement is reduced by 50%. The technique succeeds in improving soil properties to approximately 5.0 m in depth depending on soil uniformity with depth.
A developed stereo particle image velocimetry (stereo-PIV) system was proposed to measure three-dimensional (3D) soil deformation around a laterally loaded pile in sand. The stereo-PIV technique extended 2D measurement to 3D based on a binocular vision model, where two cameras with a well geometrical setting were utilized to image the same object simultaneously. This system utilized two open software packages and some simple programs in MATLAB, which can easily be adjusted to meet user needs at a low cost. The failure planes form an angle with the horizontal line, which are measured at 27°–29°, approximately three-fourths of the frictional angle of soil. The edge of the strain wedge formed in front of the pile is an arc, which is slightly different from the straight line reported in the literature. The active and passive influence zones are about twice and six times of the diameter of the pile, respectively. The test demonstrates the good performance and feasibility of this stereo-PIV system for more advanced geotechnical testing.
Triaxial cyclic loading tests have been performed to assess the influence of plastic deformation on inelastic deformational properties of anisotropic argillite with bedding planes which is regarded as a kind of transversely isotropic media. Considering argillite’s anisotropy and inelastic deformational properties, theoretical formulae for calculating oriented elastic parameters were deduced by the unloading curves, which can be better fitted for the description of its elasticity than loading curves. Test results indicate that with the growth of accumulated plastic, strain, the apparent elastic modulus of argillite decreases in a form of exponential decay function, whereas the apparent Poisson ratio increase in a form of power equation. A ratio of unloading recoverable strain to the total strain increment occurred during a loading cycle is defined to illustrate the characteristic relations between anisotropic coupled elasto-plastic deformation and plastic strain. It is significant to observe that high stress level and plastic history have an inhibiting effect on argillite anisotropy.
Complex slopes are characterized by large numbers of failure modes, cut sets or link sets, or by statistical dependence between the failure modes. For such slopes, a systematic quantitative method, or matrix-based system reliability method, was described and improved for their reliability analysis. A construction formula of event vector cE was suggested to solve the difficulty of identifying any component E in sample space, and event vector c of system events can be calculated based on it, then the bounds of system failure probability can be obtained with the given probability information. The improved method was illustrated for four copper mine slopes with multiple failure modes, and the bounds of system failure probabilities were calculated by self-compiling program on the platform of the software MATLAB. Comparison in results from matrix-based system reliability method and two generic system methods suggests that identical accuracy could be obtained by all methods if there are only a few failure modes in slope system. Otherwise, the bounds by the Ditlevsen method or Cornell method are expanded obviously with the increase of failure modes and their precision can hardly satisfy the requirement of practical engineering while the results from the proposed method are still accurate enough.
In order to have a good understanding of the behavior of wet shotcrete as a support element interacting with the rock mass, mechanism of wet shotcrete interacting with rock in support systems was analyzed through theoretical, numerical study and analytical analysis. A new model of distribution of rock stress state after wet shotcrete was applied, which includes shotcrete layer, composite layer, strengthening layer, plastic layer and elastic layer, and a full illustration of the rock mass stress state was given after shotcrete interacting with rock mass. At the same time, numerical analysis with FLAC gives a stress distribution along the monitor line, respectively, at the sidewall and roof of the tunnel. The displacement obviously decreases with the depth of rock, the tangential stress for tunnel supported by shotcrete is lower than that without shotcrete, and radial stress for tunnel supported by shotcrete is higher than that without shotcrete. It has been demonstrated by AIRY’S stress function, which gives a reasonable solution. Finally, the application of wet shotcrete in Jinfeng Gold Mine shows that the displacement of tunnel decreases obviously in sidewall and roof.
The effects of the different landforms of the cutting leeward on the aerodynamic performance of high-speed trains were analyzed based on the three-dimensional, steady, and incompressible Navier-Stokes equation and k-ɛ double-equation turbulent model. Results show that aerodynamic forces increase with the cutting leeward slope decreasing. The maximum adding value of lateral force, lift force, and overturning moment are 147%, 44.3%, and 107%, respectively, when the slope varies from 0.67 to −0.67, and the changes in the cutting leeward landform have more effects on the aerodynamic performance when the train is running in the line No. 2 than in the line No. 1. The aerodynamic forces, except the resistance force, sharply increase with the slope depth decreasing. By comparing the circumstance of the cutting depth H= −8 m with that of H=8 m, the resistance force, lateral force, lift force, and overturning moment increase by 26.0%, 251%, 67.3% and 177%, respectively. With the wind angle increasing, the resistance force is nonmonotonic, whereas other forces continuously rise. Under three special landforms, the changes in the law of aerodynamic forces with the wind angle are almost similar to one another.
The remain passenger problem at subway station platform was defined initially, and the period variation of remain passenger queues at platform was investigated through arriving and boarding analyses. Taking remain passenger queues at platform as dynamic stochastic process, a new probabilistic queuing method was developed based on probabilistic theory and discrete time Markov chain theory. This model can calculate remain passenger queues while considering different directions. Considering the stable or variable train arriving period and different platform crossing types, a series of model deformation research was carried out. The probabilistic approach allows to capture the cyclic behavior of queues, measures the uncertainty of a queue state prediction by computing the evolution of its probability in time, and gives any temporal distribution of the arrivals. Compared with the actual data, the deviation of experimental results is less than 20%, which shows the efficiency of probabilistic approach clearly.