A yttrium-containing high-temperature titanium alloy (Ti-6Al-2.7Sn-4Zr-0.4Mo-0.45Si-0.1Y, mass fraction, %) has been additively manufactured using selective electron beam melting (SEBM). The resulting microstructure and textures were studied using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and electron backscattered diffraction (EBSD) and compared with the conventionally manufactured form. A notable distinct difference of microstructures is that additive manufacturing by SEBM enables homogeneous precipitation of fine Y₂O₃ dispersoids in the size range of 50-250 nm throughout the as-fabricated alloy, despite the presence of just trace levels of oxygen (7×10^-4, mass fraction) and yttrium (10^-3, mass fraction) in the alloy. In contrast, the conventionally manufactured alloy shows inhomogeneously distributed coarse Y₂O₃ precipitates, including cracked or debonded Y₂O₃ particles.

For contact dominated numerical control (NC) bending process of tube, the effect of friction on bending deformation behaviors should be focused on to achieve precision bending forming. A three dimensional (3D) elastic-plastic finite element (FE) model of NC bending process was established under ABAQUS/Explicit platform, and its reliability was validated by the experiment. Then, numerical study on bending deformation behaviors under different frictions between tube and various dies was explored from multiple aspects such as wrinkling, wall thickness change and cross section deformation. The results show that the large friction of wiper die–tube reduces the wrinkling wave ratio η and cross section deformation degree ΔD and increases the wall thinning degree Δt. The large friction of mandrel–tube causes large η, Δt and ΔD, and the onset of wrinkling near clamp die. The large friction of pressure die–tube reduces Δt and ΔD, and the friction on this interface has little effect on η. The large friction of bending die–tube reduces η and ΔD, and the friction on this interface has little effect on Δt. The reasonable friction coefficients on wiper die–tube, mandrel–tube, pressure die–tube and bending die–tube of 21-6-9 (0Cr21Ni6Mn9N) stainless steel tube in NC bending are 0.05–0.15, 0.05–0.15, 0.25–0.35 and 0.25–0.35, respectively. The results can provide a guideline for applying the friction conditions to establish the robust bending environment for stable and precise bending deformation of tube bending.

Al-Si/15%SiC_p (volume fraction) composites with different silicon contents were fabricated by spray deposition technique, and typical microstructures of these composites were studied by optical microscopy (OM). Dry sliding wear tests were carried out using a block-on-ring wear machine to investigate the effect of applied load range of 10–220 N on the wear and friction behavior of these composites sliding against SAE 52100 grade bearing steel. Scanning electron microscopy (SEM) and energy-dispersive X-ray microanalysis (EDAX) were utilized to examine the morphologies of the worn surfaces in order to observe the wear characteristics and investigate the wear mechanism. The results show that the wear behavior of these composites is dependent on the silicon content in the matrix alloy and the applied load. Al-Si/15%SiC_p composites with higher silicon content exhibit better wear resistance in the applied load range. Under lower loads, the major wear mechanisms are oxidation wear and abrasive wear for all tested composites. Under higher loads, severe adhesive wear becomes the main wear mechanisms for Al-7Si/15%SiC_p and Al-13Si/15%SiC_p composites, while Al-20Si/15%SiC_p presents a compound wear mechanism, consisting of oxidation, abrasive wear and adhesion wear.

The synthesis and transport properties of the Li₆La₃BiSnO₁₂ solid electrolyte by a solid-state reaction were reported. The condition to synthesize the Li₆La₃BiSnO₁₂ is 785 °C for 36 h in air. The refined lattice constant of Li₆La₃BiSnO₁₂ is 13.007 Å. Qualitative phase analysis by X-ray powder diffraction patterns combined with the Rietveld method reveals garnet type compounds as major phases. The Li-ion conductivity of the prepared Li₆La₃BiSnO₁₂ is 0.85×10^–4 S/cm at 22 °C, which is comparable with that of the Li₅La₃Bi₂O₁₂. The Li₆La₃BiSnO₁₂ compounds are chemically stable against LiCoO₂ which is widely used as cathode material up to 700 °C but not against the LiMn₂O₄ if the temperature is higher than 550 °C. The Li₆La₃BiSnO₁₂ exhibits higher chemical stability than Li₅La₃Bi₂O₁₂, which is due to Sn substitution for Bi.

Extracting vanadium and removing phosphorus simultaneously by adding CaO containing materials to V-bearing hot metal were investigated under the condition of simulating the process of vanadium extraction with insufficiently supplying oxygen in converter. Through preliminary experiments, 3 h and 1375 °C were chosen as the optimum holding time and reaction temperature for formal experiments, respectively. The results of the formal experiments suggest that making basic slag can extract vanadium and remove phosphorus simultaneously. The vanadium extraction rate (η_V) and phosphorus removal rate (η_P) both increase with an increase in the basicity of the original slag materials and the Fe₂O₃ contents. The vanadium distribution ratio (L′_V) is about an order of magnitude greater than the phosphorus distribution ratio (L′_P), but the latter is more sensitive to slag basicity than the former. The phosphorus distribution ratio is beyond 6 when the basicity of the original slag materials is beyond 1, which indicates a much better performance of phosphorus removal compared to the phosphorus removal in the current process. Therefore, it is very feasible to properly raise slag basicity to remove phosphorus with consideration of the grade of vanadium slag. The relations between η_V and η_P, and between L′_V and L′_P are linear under the experimental conditions.

An attempt was made to build up a thick and compact oxide layer rapidly by pre-treating the Pb-Ag-Nd anode in fluoride-containing H₂SO₄ solution. The passivation reaction of Pb-Ag-Nd anode during pre-treatment process was investigated using cyclic voltammetry, linear scanning voltammetry, environmental scanning electron microscopy and X-ray diffraction analysis. The results show that PbF₂ and PbSO₄ are formed near the potential of Pb/PbSO₄ couple. The pre-treatment in fluoride-containing H₂SO₄ solution contributes to the formation of a thick, compact and adherent passive film. Furthermore, pre-treatment in fluoride-containing H₂SO₄ solution also facilitates the formation of PbO₂ on the anodic layer, and the reason could be attributed to the formation of more PbF₂ and PbSO₄ during the pre-treatment which tend to transform to PbO₂ during the following electrowinning process. In addition, the anodic layer on anode with pre-treatment in fluoride-containing H₂SO₄ solution is thick and compact, and its predominant composition is β-PbO₂. In summary, the pre-treatment in fluoride-containing H₂SO₄ solution benefits the formation of a desirable protective layer in a short time.)

Desulfurization experiments of CuO, γ-Al₂O₃ and CuO/γ-Al₂O₃ were made in simulated flue gas by means of thermogravimetric analysis. It is found that reaction activities of CuO supported on γ-Al₂O₃ could be highly improved. Desulfurization kinetics of CuO/γ-Al₂O₃ was studied in the temperature range of 250 °C-400 °C and SO2 concentration of 0.1%-0.9%. The experimental data were tested and compared with kinetics models of volume reaction model (VRM), grain size model (GSM), random pore model (RPM) and pore-blocking model (PBM). Correlation analysis shows that VRM and RPM models do not fit experimental data well. GSM contradicts with the changes in the physical and chemical properties of CuO/γ-Al₂O₃ as the desulfurization proceeds. It is found that PBM is consistent with the change of pore structure of CuO/γ-Al₂O₃ sorbent during desulfurization process and predicts the conversion-time curves of the sorbent well. Meanwhile, kinetics parameters are obtained and discussed.

In order to fundamentally solve the acidification problem of high sulfur-containing bauxite during storage, by simulating the environment of minerals storage in laboratory, the acidification mechanism and influencing factors of high sulfur-containing bauxite were studied and confirmed using the single variable method to control the atmosphere, water and other variables. The results show that the acidification is mostly caused by the oxidation of sulfur-containing bauxite, which is mainly the natural oxidation of Pyrite (FeS₂), then the alkaline minerals dissolute in the presence of water, leading to the acidification phenomenon, which is influenced by moisture and air flow. Finally, more acid-producing substances are formed, resulting in the acidification of high sulfur-containing bauxite. The acidification of high sulfur-containing bauxite results from the combined effect of the oxygen in the air and water, which can be significantly alleviated by controlling the diffusion of the oxygen in air.

Solid wastes derived from metallurgical industries pose a significant threat to environment. The utilization and disposal of these solid wastes are the major concern in the world. Semi-coke generated in coal-based direct reduction process of iron ore is a by-product and its suitable utilization is not available so far. In order to handle it properly, the characteristics of this by-product were comprehensively investigated. A series of analysis methods were used to demonstrate its mineral compositions, petrography and physico-chemical properties. The results reveal that the semi-coke has poor washability. The fixed carbon content of semi-coke reaches 76.11% and the gross calorific value is 28.10 MJ/kg, both of which are similar to those of traditional sinter coke breeze. Also, semi-coke ash possesses lower content of SiO₂, Al₂O₃, S and higher content of CaO and MgO, which could improve the strength of sinter ore when partially substituting for coke breeze in sintering. Semi-coke features well-development porous structure and higher reaction activity, which predicts that the sintering speed could be elevated to some extent when employing it as a partial replacement of coke breeze, so the studies further suggest that the potential adverse effect of the high reactivity on sintering process could be weakened by adequately coarsening the semi-coke’s particle size.

Biological desilication process is an effective way to remove silicate from rutile so that high purity rutile could be obtained. However, little is known about the molecular mechanism of this process. In this work, a newly developed rutile bio-desilication reactor was applied to enrich rutile from rough rutile concentrate obtained from Nanzhao rutile mine and a comprehensive high through-put functional gene array (GeoChip 4.0) was used to analyze the functional gene diversity, structure and metabolic potential of microbial communities in the biological desilication reactor. The results show that TiO₂ grade of the rutile concentrate could increase from 78.21% to above 90% and the recovery rate could reach to 96% or more in 8-12 d. The results also show that almost all the key functional genes involved in the geochemical cycling process, totally 4324 and 4983 functional microorganism genes, are detected in the liquid and ore surface, respectively. There are totally 712 and 831 functional genes involved in nitrogen cycling for liquid and ore surface samples, respectively. The relative abundance of functional genes involved in the phosphorus and sulfur cycling is higher in the ore surface than liquid. These results indicate that nitrogen, phosphorus and sulfur cycling are also present in the desiliconization process of rutile. Acetogenesis genes are detected in the liquid and ore surface, which indicates that the desiliconizing process mainly depends on the function of acetic acid and other organic acids. Four silicon transporting genes are also detected in the sample, which proves that the bacteria have the potential to transfer silicon in the molecule level. It is shown that bio-desilication is an effective and environmental-friendly way for enrichment of rough rutile concentrate and presents an overview of functional diversity and structure of desilication microbial communities, which also provides insights into our understanding of metabolic potential in biological desilication reactor ecosystems.

In order to decrease the solubility of PbSO₄ and enhance lead recovery from PbSO₄ bearing wastes, CO was employed as a reductant to transform PbSO₄ into PbS. Reaction system was established and reductive thermodynamics of PbSO₄ was calculated by software HSC 5.0. The effects of gas concentration, reaction temperature, time and mass of sample on reduction of PbSO₄ were examined by thermogravimetry (TG) and XRD. Roasting tests further verify the conclusions of thermodynamic and TG analyses. The results show that increasing temperature in the reasonable range and CO content are favorable for the formation of PbS. The reduction process is controlled by chemical reaction and calculation value of the activation energy is 47.88 kJ/mol.

An environment friendly bio-surfactant of rhamnolipid (RL) was used as a solvent. The enzymatic reaction of oleic acid catalyzed by lipase and lignin peroxidase (lip) was evaluated. The optimum conditions of enzymatic reaction catalyzed by lipase (lip) were water to amphiphile molar ratio of 30 (20), RL of 60 (60) critical micelle concentration (CMC), pH of 7.0 (3.0) and temperature of 40 (30) °C, respectively. The change of enzyme conformation indicates that, for catalytic of lipase, water content is the most important factor of the enzymatic reaction of oleic acid, and pH for lip. With individual optimum conditions, the enzymatic efficiency of oleic acid catalyzed by lipase is higher than that by lip. In the presence of ethanol, the enzymatic reaction of oleic acid catalyzed by lipase suits Ping-Pong Bi-Bi mechanism. As an alternative to chemical reversed micelles, the RL reversed micelles are promising methods to enzymatic reaction of oleic acid.

The electrochemical degradation of reed pulp black liquor containing lignin pretreated by acidification method was investigated using a three-dimensional electrode reactor. Using activated carbon as particle electrode, the effects of pH value, reaction temperature, electrolysis time and current on residual concentration of total organic carbon (TOC) were discussed in detail. The optimal conditions were obtained: pH 2.5, influent flow rate of 200 mL/min, 25 °C, 300 mA and 2 h of electrolysis time, and the removal efficiency of TOC maintains at 35.57 %. The results of the electrochemical method indicate that •OH radicals are produced in activated carbon anode in the electrolysis process and then adsorbed on the activated carbon surface. Microcell consists of •OH radicals and the absorbed lignin. With the microcell reaction, the lignin is degraded, while the anodic polarized curve illustrates that the lignin is obviously oxidized in the anode. The contributions of direct and indirect electrolyses to the TOC removal ratio are about 50%, respectively.

Walking is the most basic and essential part of the activities of daily living. To enable the elderly and non-ambulatory gait-impaired patients, the repetitive practice of this task, a novel gait training robot (GTR) was designed followed the end-effector principle, and an active partial body weight support (PBWS) system was introduced to facilitate successful gait training. For successful establishment of a walking gait on the GTR with PBWS, the motion laws of the GTR were planned to enable the phase distribution relationships of the cycle step, and the center of gravity (COG) trajectory of the human body during gait training on the GTR was measured. A coordinated control strategy was proposed based on the impedance control principle. A robotic prototype was developed as a platform for evaluating the design concepts and control strategies. Preliminary gait training with a healthy subject was implemented by the robotic-assisted gait training system and the experimental results are encouraging.

A new method of manufacturing micro-flow channels on graphite composite bipolar plate (GCBPP) microplaning using specially designed multi-tooth tool is proposed. In this method, several or even dozens of parallel micro-flow channels ranging from 100 µm to 500 µm in width can be produced simultaneously. But, edge chippings easily occur on the rib surface of GCBPP during microplaning due to brittleness of graphite composites. Experimental results show that edge chippings result in the increase of contact resistance between bipolar plate and carbon paper at low compaction force. While the edge chippings scarcely exert influence on the contact resistance at high compaction force. Contrary to conventional view, the edge chippings can significantly improve performance of microfuel cell and big edge chippings outperform small edge chippings. In addition, the influence of technical parameters on edge chippings was investigated in order to obtain big, but not oversized edge chippings.

To gain a thorough understanding of the load state of parallel kinematic machines (PKMs), a methodology of elastodynamic modeling and joint reaction prediction is proposed. For this purpose, a Sprint Z3 model is used as a case study to illustrate the process of joint reaction analysis. The substructure synthesis method is applied to deriving an analytical elastodynamic model for the 3-PRS PKM device, in which the compliances of limbs and joints are considered. Each limb assembly is modeled as a spatial beam with non-uniform cross-section supported by lumped virtual springs at the centers of revolute and spherical joints. By introducing the deformation compatibility conditions between the limbs and the platform, the governing equations of motion of the system are obtained. After degenerating the governing equations into quasi-static equations, the effects of the gravity on system deflections and joint reactions are investigated with the purpose of providing useful information for the kinematic calibration and component strength calculations as well as structural optimizations of the 3-PRS PKM module. The simulation results indicate that the elastic deformation of the moving platform in the direction of gravity caused by gravity is quite large and cannot be ignored. Meanwhile, the distributions of joint reactions are axisymmetric and position-dependent. It is worthy to note that the proposed elastodynamic modeling method combines the benefits of accuracy of finite element method and concision of analytical method so that it can be used to predict the stiffness characteristics and joint reactions of a PKM throughout its entire workspace in a quick and accurate manner. Moreover, the present model can also be easily applied to evaluating the overall rigidity performance as well as statics of other PKMs with high efficiency after minor modifications.

Based on parameter design language, a program of progressive failure analysis in composite structures is proposed. In this program, the relationship between macro- and micro-mechanics is established and the macro stress distribution of the composite structure is calculated by commercial finite element software. According to the macro-stress, the damaged point is found and the micro-stress distribution of representative volume element is calculated by finite-volume direct averaging micromechanics (FVDAM). Compared with the results calculated by failure criterion based on macro-stress field (the maximum stress criteria and Hashin criteria) and micro-stress field (Huang model), it is proven that the failure analysis based on macro- and micro-mechanics model is feasible and efficient.

In order to specify the characteristics of un-overloaded centrifugal pumps, the IH100-65-200 pump was chosen as the model pump. Different calculation models for centrifugal pumps were established under different pumping chamber sectional parameters. In the numerical simulation of the centrifugal pumps flow field, the shaft power, head, efficiency, and the changes of the internal flow field under different sectional areas and sectional shapes were studied with the RNG k-ε turbulence model, and the influence of the pumping chamber section characteristics of the non-overloaded centrifugal pumps were analyzed. The results show that sectional areas have a significant impact on the non-overload characteristics of centrifugal pumps. The shaft power and head of centrifugal pump are increasing with a lager sectional area, by which the gradient of head curves decreases. The efficiency is improved under a large flow rate condition, but the head and the efficiency are reduced at a small flow rate. It is also observed that the sectional shapes have less influence on the shaft power, the hydraulic performance and flow field characteristics of a centrifugal pump.

In order to increase productivity and reduce energy consumption of steelmaking-continuous casting (SCC) production process, especially with complicated technological routes, the cross entropy (CE) method was adopted to optimize the SCC production scheduling (SCCPS) problem. Based on the CE method, a matrix encoding scheme was proposed and a backward decoding method was used to generate a reasonable schedule. To describe the distribution of the solution space, a probability distribution model was built and used to generate individuals. In addition, the probability updating mechanism of the probability distribution model was proposed which helps to find the optimal individual gradually. Because of the poor stability and premature convergence of the standard cross entropy (SCE) algorithm, the improved cross entropy (ICE) algorithm was proposed with the following improvements: individual generation mechanism combined with heuristic rules, retention mechanism of the optimal individual, local search mechanism and dynamic parameters of the algorithm. Simulation experiments validate that the CE method is effective in solving the SCCPS problem with complicated technological routes and the ICE algorithm proposed has superior performance to the SCE algorithm and the genetic algorithm (GA).

Based on RNG k-ε turbulence model and sliding grid technique, solid-liquid two-phase three-dimensional (3-D) unsteady turbulence of full passage in slurry pump was simulated by means of Fluent software. The effects of unsteady flow characteristics on solid-liquid two-phase flow and pump performance were researched under design condition. The results show that clocking effect has a significant influence on the flow in pump, and the fluctuation of flow velocity and pressure is obvious, particularly near the volute tongue, at the position of small sections of volute and within diffuser. Clocking effect has a more influence on liquid-phase than on solid-phase, and the wake-jet structure of relative velocity of solid-phase is less obvious than liquid-phase near the volute tongue and the impeller passage outlet. The fluctuation of relative velocity of solid-phase flow is 7.6% smaller than liquid-phase flow at the impeller outlet on circular path. Head and radial forces of the impeller are 8.1% and 85.7% of fluctuation, respectively. The results provide a theoretical basis for further research for turbulence, improving efficient, reducing the hydraulic losses and wear. Finally, field tests were carried out to verify the operation and wear of slurry pump.

Warehouse operation has become a critical activity in supply chain. Position information of pallets is important in warehouse management which can enhance the efficiency of pallets picking and sortation. Radio frequency identification (RFID) has been widely used in warehouse for item identifying. Meanwhile, RFID technology also has great potential for pallets localization which is underutilized in warehouse management. RFID-based checking-in and inventory systems have been applied in warehouse management by many enterprises. Localization approach is studied, which is compatible with existing RFID checking-in and inventory systems. A novel RFID localization approach is proposed for pallets checking-in. Phase variation of nearby tags was utilized to estimate the position of added pallets. A novel inventory localization approach combing angle of arrival (AOA) measurement and received signal strength (RSS) is also proposed for pallets inventory. Experiments were carried out using standard UHF passive RFID system. Experimental results show an acceptable localization accuracy which can satisfy the requirement of warehouse management.

An important problem in demand planning for energy consumption is developing an accurate energy forecasting model. In fact, it is not possible to allocate the energy resources in an optimal manner without having accurate demand value. A new energy forecasting model was proposed based on the back-propagation (BP) type neural network and imperialist competitive algorithm. The proposed method offers the advantage of local search ability of BP technique and global search ability of imperialist competitive algorithm. Two types of empirical data regarding the energy demand (gross domestic product (GDP), population, import, export and energy demand) in Turkey from 1979 to 2005 and electricity demand (population, GDP, total revenue from exporting industrial products and electricity consumption) in Thailand from 1986 to 2010 were investigated to demonstrate the applicability and merits of the present method. The performance of the proposed model is found to be better than that of conventional back-propagation neural network with low mean absolute error.

The main objective of multiuser orthogonal frequency division multiple access (MU-OFDM) is to maximize the total system capacity in wireless communication systems. Thus, the problem in MU-OFDM system is the adaptive allocation of the resources (subcarriers, bits and power) to different users subject to several restrictions to maximize the total system capacity. In this work, a proposed subcarrier allocation algorithm was presented to assign the subcarriers with highest channel gain to the users. After the subcarrier allocation, subcarrier gain-based power allocation (SGPA) was employed for power and bit loading. The simulation results show that the proposed subcarrier-power allocation scheme can achieve high total system capacity and good fairness in allocating the resources to the users with slightly high computational complexity compared to the existing subcarrier allocation algorithms.

Petrographic analysis combined with various techniques, such as thin section identification, fluid inclusions, isotopic data, petro-physical property testing and oil testing results, was used to study diagenetic evolution and its effect on reservoir-quality of fan delta reservoirs of Es4s in the Bonan sag. The diagenesis is principally characterized by strong compaction, undercompaction, multi-phase of dissolution and cementation. Compaction played a more important role than cementation in destroying the primary porosity of the sandstones. The reservoirs have experienced complicated diagenetic environment evolution of “weak alkaline- acid-alkalinity-acid-weak alkalinity” and two-stage of hydrocarbon filling. The diagenetic sequences are summarized as “early compaction/early pyrite/gypsum/calcite/dolomite cementation→feldspar dissolution/the first stage of quartz overgrowth → early hydrocarbon filling→quartz dissolution/anhydrite/Fe-carbonate cementation→Fe-carbonate dissolution/feldspar dissolution/ the second stage of quartz overgrowth → later hydrocarbon filling→later pyrite cementation. In the same diagenetic context, the diagenetic evolution processes that occurred in different sub/micro-facies during progressive burial have resulted in heterogeneous reservoir properties and oiliness. The braided channel reservoirs in fan delta plain are poorly sorted with high matrix contents. The physical properties decrease continually due to the principally strong compaction and weak dissolution. The present properties of braided channel reservoirs are extremely poor, which is evidenced by few oil layers developed in relatively shallow strata while dry layers entirely in deep. The reservoirs both in the underwater distributary channels and mouth bars are well sorted and have a strong ability to resist compaction. Abundant pores are developed in medium-deep strata because of modifications by two-stage of acidic dissolution and hydrocarbon filling. The present properties are relatively well both in the underwater distributary channels and mouth bars and plenty of oil layers are developed in different burial depth. The present reservoir properties both in interdistributary channel and pre-fan delta are poor caused by extensively cementation. Small amounts of oil layers, oil-water layers and oil-bearing layers are developed in relatively shallow strata while dry layers totally in deep.

The present work ascertains the feasibility of oil residue treatment for stabilizing wind-blown sand dunes. Various combinations of natural collapsible saline from the Jandaq desert of Iran and oil residue from distillation towers of Iranian refineries were tested in laboratory experiments. Stabilized sands were evaluated in terms of geotechnical properties, permeability, and oil retention characteristics (i.e. bonding mechanisms, leaching and migrating behaviour of oil residue from the stabilized sands). Since the presence of oil residue in soils can pose an environmental threat, the optimum retention capacity of the stabilized sands is of critical concern. Relative to sand that was not augmented with oil residue, specimens made of 7% oil residues had the highest compressive strength, significantly higher cohesion and load bearing capacity, and considerably lower permeability. The effect of distilled water, saline water and municipal sewage on prepared specimens were also evaluated.

Conventional model tests and centrifuge tests are frequently used to investigate seepage erosion. However, the centrifugal test method may not be efficient according to the results of hydraulic conductivity tests and piping erosion tests. The reason why seepage deformation in model tests may deviate from similarity was first discussed in this work. Then, the similarity criterion for seepage deformation in porous media was improved based on the extended Darcy-Brinkman-Forchheimer equation. Finally, the coupled particle flow code–computational fluid dynamics (PFC-CFD) model at the mesoscopic level was proposed to verify the derived similarity criterion. The proposed model maximizes its potential to simulate seepage erosion via the discrete element method and satisfy the similarity criterion by adjusting particle size. The numerical simulations achieved identical results with the prototype, thus indicating that the PFC-CFD model that satisfies the improved similarity criterion can accurately reproduce the processes of seepage erosion at the mesoscopic level.

The nonlinear Hoek-Brown failure criterion was introduced to limit analysis by applying the tangent method. Based on the failure mechanism of double-logarithmic spiral curves on the face of deep rock tunnels, the analytical solutions of collapse pressure were derived through utilizing the virtual power principle in the case of pore water, and the optimal solutions of collapse pressure were obtained by using the optimization programs of mathematical model with regard of a maximum problem. In comparison with existing research with the same parameters, the consistency of change rule shows the validity of the proposed method. Moreover, parametric study indicates that nonlinear Hoek-Brown failure criterion and pore water pressure have great influence on collapse pressure and failure shape of tunnel faces in deep rock masses, particularly when the surrounding rock is too weak or under the condition of great disturbance and abundant ground water, and in this case, supporting measures should be intensified so as to prevent the occurrence of collapse.

Direct shear tests were conducted on the rock joints under constant normal load (CNL), while the acoustic emission (AE) signals generated during shear tests were monitored with PAC Micro-II system. Before and after shearing, the surfaces of rock joints were measured by the Talysurf CLI 2000. By correlating the AE events with the shear stress-shear displacement curve, one can observe four periods of the whole course of shearing of rock joints. By the contrast of AE location and actual damage zone, it is elucidated that the AE event is related to the morphology of the joint. With the increase of shearing times, the shear behavior of rock joints gradually presents from the response of brittle behavior to that of ductile behavior. By combining the results of topography measurement, four morphological parameters of joint surface, S_p (the maximum height of joint surface), N (number of islands), A (projection area) and V (volume of joint) were introduced, which decrease with shearing. Both the joint roughness coefficient (JRC) and joint matching coefficient (JMC) drop with shearing, and the shear strength of rock joints can be predicted by the JRC-JMC model. It establishes the relationship between micro-topography and macroscopic strength, which have the same change rule with shearing.

The understanding of the rock deformation and failure process and the development of appropriate constitutive models are the basis for solving problems in rock engineering. In order to investigate progressive failure behavior in brittle rocks, a modified constitutive model was developed which follows the principles of the continuum damage mechanics method. It incorporates non-linear Hoek-Brown failure criterion, confining pressure-dependent strength degradation and volume dilation laws, and is able to represent the nonlinear degradation and dilation behaviors of brittle rocks in the post-failure region. A series of triaxial compression tests were carried out on Eibenstock (Germany) granite samples. Based on a lab data fitting procedure, a consistent parameter set for the modified constitutive model was deduced and implemented into the numerical code FLAC^3D. The good agreement between numerical and laboratory results indicates that the modified constitutive law is well suited to represent the nonlinear mechanical behavior of brittle rock especially in the post-failure region.

The central buckle, which is often used in a suspension bridge, can improve bridges’ performance in the actual operation condition. The influence of the central buckle on natural vibration characteristics and bridge-deck driving comfort of a long-span suspension bridge is studied by using a case study of Siduhe Suspension Bridge in China. Based on the finite element software ANSYS and independently complied program, the influence of the central buckle on the structure force-applied characteristics of a long-span suspension bridge has been explored. The results show that the huge increases of natural frequencies can result in the presence of central buckles because of the increases of bending and torsional rigidities. The central buckle basically makes the stiffening girders and cables within the triangular area covered as a relatively approximate rigid area. Hence, the central buckle can reduce the torsional displacement of the main girder. However, the increases of bending and torsional rigidities have little influence on the impact factor, which is obtained by using vehicle-bridge coupled vibration analysis. This means that the central buckle has little effect on the comfort indices. In addition, it is found that the central buckle can enhance the bridge deck’s driving stability due to the decrease of the torsional displacements of the main girder.

To realize a stable addition of foaming agent used for foam technology, a new adding method using the jet cavitation was introduced, and its performance was investigated experimentally under different operating conditions. Experimental results show that the bubble region in the jet device has a constant vapor pressure, which creates a good condition for liquid absorption, while it shrinks with increasing outlet pressure. The liquid absorption amount keeps unchanged when the outlet pressure is lower than a critical value. The critical outlet pressure increases by 40% with decreasing cavitation absorption amount, which is especially suitable for mini-flow quantitative addition of foaming agent used for foam dust suppression. Its effectiveness on suppressing mine dust was evaluated in a heading face of underground coal mines. Field application indicates that the reliable and simple foaming system adopting the new adding method makes a marked dust suppression effect. The working environment of heading face is significantly improved, ensuring the safe tunneling and personal security.

The feasibility of longer spans relies on the successful implementation of new high-strength light weight materials such as carbon fiber reinforced polymer (CFRP). First, a dimensionless equilibrium equation and the corresponding compatibility equation are established to develop the cable force equation and cable displacement governing equation for suspension cables, respectively. Subsequently, the inextensible cable case is introduced. The formula of the Irvine parameter is considered and its physical interpretation as well as its relationship with the chord gravity stiffness is presented. The influences on the increment of cable force and displacement by λ² and load ratio p′ are analyzed, respectively. Based on these assumptions and the analytical formulations, a 2000 m span suspension cable is utilized as an example to verify the proposed formulation and the responses of the relative increment of cable force and cable displacement under symmetrical and asymmetrical loads are studied and presented. In each case, the deflections resulting from elastic elongation or solely due to geometrical displacement are analyzed for the lower elastic modulus CFRP. Finally, in comparison with steel cables, the influences on the cable force equation and the governing displacement equation by span and rise span ratio are analyzed. Moreover, the influences on the static performance of suspension bridge by span and sag ratios are also analyzed. The substantive characteristics of the static performance of super span CFRP suspension bridges are clarified and the superiority and the characteristics of CFRP cable structure are demonstrated analytically.

Experimental study was carried out on the in-plane bending behavior of glass plates without lateral supports, and the effects of the factors, such as height-to-span ratio, on the stability of glass panels were studied. Results show that the in-plane bending glass plates with both ends simply supported and their upper edge free lose overall stability under loads, which belongs to the limit-point type of instability. It is found that the buckling load increases linearly with the increase of height-to-span ratio of the glass plates. The lateral stress of in-plane bending glass plates without lateral supports increases linearly under loads; while the large-area stress increases nonlinearly and the lateral stress is not the controlling factor of instability. In finite element analysis, the first buckling mode is regarded as the initial imperfection and imposed on the model as 1/1000 of the span of the components. The numerical buckling load according to the theory of large deflection is less than the experiment result, which is more conservative and can provide some reference for design. For the design method, when the in-plane load is imposed on the glass plate, its lateral strength and the deflection should be verified. Considering the stability of the in-plane bending glass plate without reliable lateral support, buckling is another possible failure mode and calls for verification.

Reinforcement inside the concrete is protected from corrosion and its damages until several years after the construction. After corrosion initiation, the cross section of reinforcement begins to reduce and often load bearing of the reinforced concrete structure will be reduced significantly. Corrosion of reinforcements in concrete in polluted and contaminated areas can occur in two ways: chloride and carbonation. In this work, meta-heuristic approach of charged system search (CSS) is used to calculate corrosion occurrence probability due to chloride ions penetration. The model efficiency is verified by comparing the available examples in technical literature and results of Monte Carlo analysis. According to the analyses performed, using different probabilistic distributions regardless of probabilistic moments based on real distribution leads to diverse results. In addition, influence of each effective parameter in corrosion occurrence varies by changing other parameters.

Twenty tests were conducted to investigate the efficiency of the intumescent coating designed to protect steel plate at the elevated temperature, by means of electrical furnace. And the factors of the initial thickness of coating and temperature of electrical furnace were considered. The high temperature response behavior of the intumescent coating was observed. And the expansion form of ultrathin intumescent coating and the temperature of the steel plate (TS) were obtained. Besides, the heat flux from expansion layer to steel plate versus time was analyzed in order to evaluate the heat transfer effect of intumescent coating on steel plate. The experimental results show that the response behaviors of the coating subjected to fire could be divided into four phases: stabilization phase, foaming expansion phase, carbonization-consumption phase and inorganic layer phase. And the net heat flux to the steel plate decreased observably in the foaming expansion phase, while the surplus white inorganic substance, which is the residue of the intumesced char layer in the inorganic layer phase under the condition of the temperature of the electrical furnace (TEF) beyond 700 °C over 1 h, has little effect on fire protection for the steel plate.

Recycled waste tires when mixed with soil can play an important role as lightweight materials in retaining walls and embankments, machine foundations and railroad track beds in seismic zones. Having high damping characteristic, rubbers can be used as either soil alternative or mixed with soil to reduce vibration when seismic loads are of great concern. Therefore, the objective of this work was to evaluate the dynamic properties of such mixtures prior to practical applications. To this reason, torsional resonant column and dynamic triaxial experiments were carried out and the effect of the important parameters like rubber content and ratio of mean grain size of rubber solids versus soil solids (D_50,r/D_50,s) on dynamic response of mixtures in a range of low to high shearing strain amplitude from about 4×10^-4% to 2.7% were investigated. Considering engineering applications, specimens were prepared almost at the maximum dry density and optimum moisture content to model a mixture layer above the ground water table and in low precipitation region. The results show that tire inclusion significantly reduces the shear modulus and increases the damping ratio of the mixtures. Also decrease in D_50,r/D_50,s causes the mixture to exhibit more rubber-like behavior. Finally, normalized shear modulus versus shearing strain amplitude curve was proposed for engineering practice.

Energy performance assessment on central air-conditioning system is essential to optimize operating, reduce operating costs, improve indoor environmental quality, and determine whether the retrofitting of the equipment is necessary. But it is difficult to evaluate it reasonably and comprehensively due to its complexity. A “holistic” approach was discussed to evaluate the energy performance of central air-conditioning system for an extra-large commercial building in a subtropical city. All procedures were described in detail, including field investigation method, field measurement instruments, data processing and data analyzing. The main factors affecting energy consumption of air-conditioning system were analyzed and the annual cooling-energy use intensity of this building was calculated and also compared with other shopping malls and other types of buildings in Guangzhou. And COP (coefficient of performance) of chiller, water transfer factor of chilled water system and cooling water system were taken into consideration. At last, the thermal comfort and indoor air quality issues were addressed. The results show that the chilled water pumps are over-sized and the indoor environmental quality should be improved. The purpose of this work is to provide reference for energy performance assessment method for air-conditioning system.

Effects of heat and mass transfer in the flow of Burgers fluid over an inclined sheet are discussed. Problems formulation and relevant analysis are given in the presence of thermal radiation and non-uniform heat source/sink. Thermal conductivity is taken temperature dependent. The nonlinear partial differential equations are simplified using boundary layer approximations. The resultant nonlinear ordinary differential equations are solved for the series solutions. The convergence of series solutions is obtained by plotting the ħ -curves for the velocity, temperature and concentration fields. Results of this work describe the role of different physical parameters involved in the problem. The Deborah numbers corresponding to relaxation time (β₁ and β₂) and angle of inclination (α) decrease the fluid velocity and concentration field. Concentration field decays as Deborah numbers corresponding to retardation time (β₃) and mixed convection parameter (G) increase. Large values of heat generation/absorption parameters A/B, and the temperature distribution across the boundary layer increase. Numerical values of local Nusselt number, −θ′(0), and local Sherwood number, −ϕ′(0), are computed and analyzed. It is found that θ′(0) increases with an increase in β₃.

The intention of this investigation is to study the effects of heat transfer and inclined magnetic field on the peristaltic flow of Williamson fluid in an asymmetric channel through porous medium. The governing two-dimensional equations are simplified under the assumption of long wavelength approximation. The simplified equations are solved for the stream function, temperature, and axial pressure gradient by using a regular perturbation method. The expression for pressure rise is computed numerically. The profiles of velocity, pressure gradient, temperature, heat transfer coefficient and stream function are sketched and interpreted for various embedded parameters and also the behavior of stream function for various wave forms is discussed through graphs. It is observed that the peristaltic velocity increases from porous medium to non-porous medium, the magnetic effects have increasing effect on the temperature, and the size of the trapped bolus decreases with the increasing of magnetic effects while the trend is reversed with the increasing of Darcy number. Moreover, limiting solutions of our problem are in close agreement with the corresponding results of the Newtonian fluid model.

High-thermal conductivity enhancement of nanofluid is one of the promising topics of the nanoscience research field. This work reports the experimental study on the preparation of graphene (GN) and multi-walled carbon nanotubes (MWCNTs) based nanofluids with the assistance of sodium dodecyl benzene sulfonate (SDBS) and sodium dodecyl sulfate (SDS) surfactants, and their thermal behaviors. The present work suggests not a solution, but a solution approach and deduces a new conclusion by trying to resolve the agglomeration problem and improve the dispersibility of nanoparticles in the base fluid. The analysis results of FESEM, thermal conductivity, diffusivity, effusivity and heat transfer coefficient enhancement ratio of nanofluid with surfactants SDS and SDBS expose strong evidence of the dispersing effect of surfactant on the making of nanofluid.

The steady two-dimensional flow of Powell-Eyring fluid is investigated. The flow is caused by a stretching surface with homogeneous-heterogeneous reactions. The governing nonlinear differential equations are reduced to the ordinary differential equations by similarity transformations. The analytic solutions are presented in series forms by homotopy analysis method (HAM). Convergence of the obtained series solutions is explicitly discussed. The physical significance of different parameters on the velocity and concentration profiles is discussed through graphical illustrations. It is noticed that the boundary layer thickness increases by increasing the Powell-Eyring fluid material parameter (ε) whereas it decreases by increasing the fluid material parameter (δ). Further, the concentration profile increases when Powell-Eyring fluid material parameters increase. The concentration is also an increasing function of Schmidt number and decreasing function of strength of homogeneous reaction. Also mass transfer rate increases for larger rate of heterogeneous reaction.

The mixing time of impact zone in liquid-continuous impinging streams reactor (LISR) is theoretically calculated by empirical model and modern micromixing model of the fluid mixing process, and the variation laws of macromixing time and micromixing time are quantitatively discussed. The results show that under a continuous and stable operating condition, as the paddle speed increases, the macromixing time and micromixing time calculated by the two models both decrease, even in a linkage equilibrium state. Simultaneously, as the paddle speed increases, the results figured by the two models tend to be consistent. It indicates that two models both are more suitable for calculation of mixing time in high paddle speed. Compared with the existing experimental results of this type of reactor, the mixing time computed in the speed of 1500 r/min is closer to it. These conclusions can provide an important reference for systematically studying the strengthening mechanism of LISR under continuous mixing conditions.

With the development of high-speed and heavy-haul railway in China, problems like insufficient thickness of ballast bed and overlarge track stiffness are obvious. Ballast may break into small particles and their contact status will deteriorate under cyclic loading, resulting in ballast degradation. Discrete element method (DEM) was used to research improved performance of ballast bed using elastic sleeper. Clusters were generated by bonding spheres to model real ballasts, while broken bonds were utilized to distinguish breakage. Two kinds of ballast beds with elastic sleeper and conventional sleeper were established, respectively. After applying cyclic loading to the models, differences of mechanical properties between two models were analyzed by contrasting their dynamic behavior indexes, such as particle contact force, sleeper settlement, vibration velocity and acceleration, breakage characteristic. The results illustrate that compared with conventional sleeper, elastic sleeper increases sleeper settlement, while reduces ballast vibration and contact force between particles, which could depress ballast breakage.

Wheel/rail relationship is a fundamental problem of railway system. Wear of wheel profiles has great effect on vehicle performance. Thus, it is important not just for the analysis of wear characteristics but for its prediction. Actual wheel profiles of the high-speed trains on service were measured in the high-speed line and the wear characteristics were analyzed which came to the following results. The wear location was centralized from −15 mm to 25 mm. The maximum wear value appeared at the area of 5 mm from tread center far from wheel flange and it was less than 1.5 mm. Then, wheel wear was fitted to get the polynomial functions on different locations and operation mileages. A binary numerical prediction model was raised to predict wheel wear. The prediction model was proved by vehicle system dynamics and wheel/rail contact geometry. The results show that the prediction model can reflect wear characteristics of measured profiles and vehicle performances.

To determinate the expressway capacity near a bus bay stop with an access, capacity models on the expressway near a bus stop with an access were developed on the basis of gap acceptance theory and queuing theory. Depending on a bus stop position to an entrance or an exit ramp, the capacity models were developed for four cases. Bus bay stops with overflow and bus bay stops without overflow were considered. A comparison of simulation experiment and model calculation was carried out. Results show that the suggested models have high accuracy and reliability, at bus arrival rate below 60 vehicles per hour (veh/h) or vehicle volumes at the entrance and the exit below 200 passenger cars units per hour (pcu/h), and there are no significant difference in the capacities for four cases. When bus arrival rate is above 240 veh/h, the capacities of all four cases will decline rapidly. With berth number increasing, the increasing of the capacities is no obvious for four cases. As the bus arrival rate and vehicle volumes at the entrance and the exit increase, bus stops located downstream of an entrance and upstream of an exit have a remarkably effect on the capacities. The latter case is much heavier than the former. Those results can be used to traffic design and optimization on urban expressway near a bus stop with an access.

Coordinated scheduling of multimode plays a pivotal role in the rapid gathering and dissipating of passengers in transport hubs. Based on the survey data, the whole-day reaching time distribution at transfer points of passengers from the dominant mode to the connecting mode was achieved. A GI/M^K/1 bulk service queuing system was constituted by putting the passengers’ reaching time distribution as the input and the connecting mode as the service institution. Through queuing theory, the relationship between average queuing length under steady-state and headway of the connecting mode was achieved. By putting the minimum total cost of system as optimization objective, the headway as decision variable, a coordinated scheduling model of multimode in intermodal transit hubs was established. At last, a dynamic scheduling strategy was generated to cope with the unexpected changes of the dominant mode. The instance analysis indicates that this model can significantly reduce passengers’ queuing time by approximately 17% with no apparently increase in departure frequency, which provides a useful solution for the coordinated scheduling of different transport modes in hubs.

In order to apply overbooking idea in Chinese railway freight industry to improve revenue, a Markov decision process (dynamic programming) model for railway freight reservation was formulated and the overbooking limit level was proposed as a control policy. However, computing the dynamic programming treatment needs six nested loops and this will be burdensome for real-world problems. To break through the calculation limit, the properties of value function were analyzed and the overbooking protection level was proposed to reduce the calculating quantity. The simulation experiments show that the overbooking protection level for the lower-fare class is higher than that for the higher-fare class, so the overbooking strategy is nested by fare class. Besides, by analyzing the influence on the overbooking strategy of freight arrival probability and cancellation probability, the proposed approach is efficient and also has a good application prospect in reality. Also, compared with the existing reservation (FCFS), the overbooking strategy performs better in the fields of vacancy reduction and revenue improvement.