The strength, fracture toughness and fatigue crack growth resistance of 7050-T7451 aluminum alloy plate with different thicknesses (35 mm and 160 mm) were investigated by means of optical microscope, scanning electron microscope and transmission electron microscope. The results show that thicker plate has lower strength and fracture toughness but higher fatigue crack growth resistance, by comparison to the thinner plate. The drop of strength is mainly attributed to grain coarsening in the thicker plate, and the increased degree of recrystallization results in the loss of K_IC. However, the coarsened grains in the thicker plate make cracks deflected and closure effect enhanced due to surface roughness increased. For both of plates, in the fracture surface subjected plain strain, a transition from transgranular dimpled fracture to intergranular dimpled fracture is observed during the fracture process.

The AZ31 alloy ingot with diameter of 110 mm and length of 3500 mm was fabricated successfully. The compositions and microstructure morphologies of the ingot at different locations were performed, which indicated that the chemical composition distributed homogeneously through the whole alloy ingot and the average grain size increased from the surface to the center. The results of the EDS and element face-scanning illustrated that the eutectic compounds mainly consisted of β-Mg₁₇Al₁₂ and a small amount of β-Mg₁₇(AlZn)₁₂. Furthermore, slight improvements of the strength and ductility were observed from the center to the surface along the axial direction of the alloy ingot, while both the strength and elongation to failure of the samples along the radial direction are higher than that along the axial direction. The fine grain strengthening was the main contributors to the strength of the as-casted AZ31 alloy.

In order to investigate the effects of brazing temperature, heating rate and cooling methods on shear strength, hardness, magnetic saturation and coercivity of the ultrafine cemented carbide, the ultrafine cemented carbide was fabricated according to conventional powder metallurgical procedures, and then brazed to the stainless steel with silver-based filler alloy by supersonic frequency induction brazing. The microstructure was observed using scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and the magnetic properties were tested utilizing coercimeter and cobalt magnetism instrument. The results show that no micro-crack is found in the cemented carbide after brazing because of silver-based sandwich compound used as filler alloy. In the melted silver layer, there is more carbon in the region adjacent to the cemented carbide. Varied shear strengths, hardnesses, magnetic saturations and coercivities are present under different brazing temperatures, heating rates and coolings. This phenomenon is correlated with some factors such as wettability and fluidity of filler alloy, brazing stress, oxidation of cemented carbide, and allotrope transition of cobalt. Shear strength reaches the maximum of 340 MPa and hardness of ultrafine cemented carbide remains 1879 HV at the brazing temperature of 730 °C. The carbon content decreases with the increase of brazing temperature, and it increases with the of increase of the heating rate. What’s more, the lowest magnetic saturation reaches 81.8% of the theoretic value, and there is no η phase found under this condition.

The interaction between a solute atom and an extended dislocation was investigated using a continuum approximation method with force multipoles. The dislocation core structure of extended dislocation was modeled with the Peierls-Nabarro model discretized with a number of infinitesimal Volterra dislocations. The interaction energy and force between a nickel solute atom and perfect and extended dislocation in copper were successfully calculated using the force multipoles. The results clearly show that the core structure of extended dislocation weakens the interaction with solute atoms. The interaction energy and force for extended dislocations are almost the half of those for perfect dislocations.

Two kinds of nickel particles with flower-like structures assembled with a number of nano-flakes were synthesized and the relationship of their morphology and microwave absorbing properties was studied. The electromagnetic parameters of these flower-like Ni were measured with vector network analyzer at 2–18 GHz frequency and the reflection losses (RL) with different sample thicknesses were calculated. The results indicate that the flower-like nickel-wax composites with the sample thickness less than 2 mm show excellent absorbing ability. This result is expected to play a guiding role in the preparation of the highly efficient absorber.

Metallic ring-shaped nanotube arrays are proposed and its optical transmission properties are studied by using finite-difference time-domain (FDTD) method. Compared with the transmission spectra of conventional circular nanotube arrays, two photonic band gaps are emerged in the transmission spectra of ring-shaped nanotube arrays, the two band gaps and transmission spectra are adjusted by the length, inner radius, intertube spacing and the dielectric constants of the core and embedding medium, and magnitude modification, redshift and blueshift of the resonance modes are observed. A metallic ring-shaped nanotube arrays for subwavelength band-stop filter in the range of visible light can be achieved. To understand its physical origin, field-interference mechanism was suggested by the field distributions. The proposed nanostructures and results may have great potential applications in subwavelength near-field optics.

A stress relaxation test has been carried out for Hastelloy C-276 at temperature of 800 °C and initial stress level of 250 MPa. Based on the experimental stress relaxation curve, the relationship between creep strain rate and stress has been derived. Then, a set of creep constitutive equations has been built and the values of constants arising in the constitutive equations have been determined by fitting the creep strain rate-stress curve. Close agreement between computed results and experimental ones is obtained for stress relaxation data. The creep constitutive equation set has been integrated with the commercial FE (finite element) solver MSC. Marc via the user defined subroutine, CRPLAW, for the vacuum hot bulge forming process modelling of Hastelloy C-276 thin-walled cylindrical workpiece. The temperature field, the radius-direction displacement field and the stress-strain field are calculated and analyzed. Furthermore, the bulging dimension and the final internal diameter of workpiece are predicted and the test results verify the reliability of the finite element method.

The effects of process parameters in rapid heat cycle moulding (RHCM) on parts warpage were investigated. A vehicle-used blue-tooth front shell (consisting of ABS material) was considered as a part example manufactured by RHCM method. The corresponding rapid heat response mould with an innovational conformal heating/cooling channel system and a dynamic mould temperature control system based on the J11-W-160 type precise temperature controller was proposed. During heating/cooling process, the mould was able to be heated from room temperature to 160 °C in 6 s and then cooled to 80 °C in 22 s. The effects of processing conditions in RHCM on part warpage were investigated based on the single factor experimental method and Taguchi theory. Results reveal that the elevated mould temperature reduces unwanted freezing during the injection stage, thus improving mouldability and enhancing part quality, whereas the overheated of mould temperature will lead to defective product. The feasible mould temperature scope in RHCM should be no higher than 140 °C, and the efficient mould temperature scope should be around the polymer heat distortion temperature. Melt temperature as well as injection pressure effects on warpage can be divided into two stages. The lower stage gives a no explicit effect on warpage whereas the higher stage leads to a quasi-linear downtrend. But others affect the warpage as a V-type fluctuation, reaching to the minimum around the heat distortion temperature. Under the same mould temperature condition, the effects of process parameters on warpage decrease according to the following order, packing time, packing pressure, melt temperature, injection pressure and cooling time, respectively.

In order to improve the bonding strength between piston alloys and cast iron ring of aluminum piston with reinforced cast iron ring, the different methods of the surface treatments (shot blasting and sand blasting) to the cast iron ring are experimented. The optical micrograph shows that an intermetallic layer and a ligulate shaped structure are formed between piston alloys and cast iron base ring. After sand blasting treatment, the ring surface is non-metal shiny, matte-like and has no obvious pits. The intermetallic layer thickness formed between piston alloys and cast iron is thinner and more equally distributed after sand blasting to the ring. The content of the graphite distributed the interfacial zone after the shot blasting treatment is little. With the increase of time by sand blasting, the hardness starts to slightly descend. The bonding strength of the sample by sand blasting is obviously higher than that by shot blasting and increases from 9.32 MPa to 19.53 MPa.

It is generally known that the large formation amount of calcium ferrite is favorable for the iron ore sintering. The effects of sintering temperature and O₂ content of inlet gas on the calcium ferrite formation characteristic of typical iron ores, including hematite, limonite, specularite and magnetite, were investigated. And the effect of O₂ content on the microstructure of the roasted briquettes was also studied in detail. The results show the amount of calcium ferrite initially increases then decreases with the increase of the sintering temperature. The temperature of maximum calcium ferrite generation amount is determined as follows: for hematite and limonite it is 1275 °C, whereas for specularite and magnetite, 1250 °C. The maximum contents of calcium ferrite for hematite, limonite, specularite and magnetite under the optimal sintering temperature are 73%, 82%, 67% and 63%, respectively. Increasing O₂ content of the airflow is advantageous to the formation of calcium ferrite. Relatively, the effect of O₂ content on the calcium ferrite formation of magnetite is the most pronounced, while O₂ content of inlet gas has little effect on the calcium ferrite formation of limonite.

Poly (methyl methacrylate) (PMMA) brushes were synthesized from silicon wafers via surface initiated atom transfer radical polymerization (SI-ATRP). Energy disperse spectroscopy (EDS) and atomic force microscopy (AFM) confirmed that PMMA brushes were successfully prepared on the silicon wafers, and the surface became more hydrophobic according to the contact angle of 69°. It is found that CuCl/1, 1, 4, 7, 10, 10-hexamethyl triethylenetetramine (HMTETA) system is more suitable than CuBr/N, N, N′, N″, N″-pentamethyl diethylenetriamine (PMDETA) system to control the free radical polymerization of MMA in solution. Nevertheless, better control on the thickness of PMMA brushes was achieved in CuBr/PMDETA than in CuCl/HMTETA due to higher activity and better reversibility of the former system.

Poly (vinyl butyral) (PVB) hollow fiber membranes were fabricated via thermally induced phase separation (TIPS). The effects of coagulation bath temperature (CBT) on the structure and performance of membranes were investigated in detail. The morphologies of the membranes were studied by scanning electron microscopy (SEM), the performances of water permeability, rejection, breaking strength and elongation were measured, respectively. The results indicate that all the membranes have the asymmetric morphology and the thickness of the skin layer decreases and the pore size of the outer layer increases with the increase of CBT. The permeability of membranes prepared at air gap 1.0 cm and take-up speed 0.253 m/s increases from 1.047×10⁻⁷ to 5.909×10⁻⁷ m³/(m²·s·kPa) with the CBT increasing from 20 °C to 40 °C, and sharply increases to 35.226×10⁻⁷ m³/(m²·s·kPa) once the CBT arrives at 50 °C. While the carbonic ink rejections have no significant decrease, totally exceed 98%, but that of acid-maleic acid copolymer greatly decreases with the increase of CBT. Both the breaking strength and elongation decrease with the increase of CBT.

To study the stereostructure by X-ray and the technology of extracting acankoreanogenin from the leaves of Acanthopanax gracilistylus W. W. Smith (AGS), the crystal structure was measured with a Bruker APEX-II area-detector diffractometer instrument and the technology of extracting in combination hydrolysis in situ (ECHS) was compared with these of traditional methods. The crystal belongs to the monoclinic system, space group P2₁, with unit cell parameters: a=(8.3652±0.0006) nm, b=(24.721±0.002) nm, and c=(14.5587±0.0011) nm, α=90 °, β=97.850 (4) °, γ=90 °, V=2982.51 nm³, D_c = 1.179 mg/m³, and the molecular number (Z) of elementary structures was 2. The comparisons show that the extraction rate of acankoreanogenin with ECHS methods is much higher than that of traditional methods. Then, central composite design-response surface methodology (CCD-RSM) was adopted for optimizing the extraction rate of ECHS methods. The optimized values of extraction parameters are as follows: for the for extraction process of acid hydrolysis are that extraction time 110.8 min, solvent-herb ratio 11.5 and acid content 5.25%; the best extraction process of basic hydrolysis are that extract time 120 min, solvent-herb ratio 8.7 and the alkali content 8.79%. Finally, the extracts were purified with decolorizing carbon after alkali solution and acid-isolation and purity of acankoreanogenin was 98.7%.

A numerical wave load model based on two-phase (water-air) Reynolds-Averaged Navier Stokes (RANS) type equations is used to evaluate hydrodynamic forces exerted on flatted-bottom seafloor mining tool during its entering ocean waves of deploying process. The discretization of the RANS equations is achieved by a finite volume approach (FV). The volume of fluid method (VOF) is employed to track the complicated free surface. A numerical wave tank is built to generate the ocean waves which are suitable for deploying seafloor mining tool. A typical deploying condition is employed to reflect the process of flatted-bottom body impacting with waves, and the pressure distribution of bottom is also presented. Four different lowering velocities are applied to obtain the time histories of maximum pressure of bottom, and it can be concluded that the pressure coefficient decreases with water velocity increasing, which is similar with ordinary water entry case. The numerical results clearly demonstrate the characteristics of flatted-bottom body entering ocean waves.

The optimal path planning for fixed-wing unmanned aerial vehicles (UAVs) in multi-target surveillance tasks (MTST) in the presence of wind is concerned. To take into account the minimal turning radius of UAVs, the Dubins model is used to approximate the dynamics of UAVs. Based on the assumption, the path planning problem of UAVs in MTST can be formulated as a Dubins traveling salesman problem (DTSP). By considering its prohibitively high computational cost, the Dubins paths under terminal heading relaxation are introduced, which leads to significant reduction of the optimization scale and difficulty of the whole problem. Meanwhile, in view of the impact of wind on UAVs’ paths, the notion of virtual target is proposed. The application of the idea successfully converts the Dubins path planning problem from an initial configuration to a target in wind into a problem of finding the minimal root of a transcendental equation. Then, the Dubins tour is derived by using differential evolution (DE) algorithm which employs random-key encoding technique to optimize the visiting sequence of waypoints. Finally, the effectiveness and efficiency of the proposed algorithm are demonstrated through computational experiments. Numerical results exhibit that the proposed algorithm can produce high quality solutions to the problem.

The primary goal of this work is to characterize the impact of weighting selection strategy and multistatic geometry on the multistatic radar performance. With the relationship between the multistatic ambiguity function (AF) and the multistatic Cramér-Rao lower bound (CRLB), the problem of calculating the multistatic AF and the multistatic CRLB as a performance metric for multistatic radar system is studied. Exactly, based on the proper selection of the system parameters, the multistatic radar performance can be significantly improved. The simulation results illustrate that the multistatic AF and the multistatic CRLB can serve as guidelines for future multistatic fusion rule development and multistatic radars deployment.

A new electro-hydraulic exciter that consists of rotary valve and micro-displacement double-functioned hydraulic cylinder was proposed to realize different kinds of waveforms. Calculated fluid dynamics (CFD) simulation of rotary valve orifice reveals that orifice exists the two-throttle phenomenon. According to the finding, the revised flow area model was established. Vibration waveforms analysis was carried out by means of mathematic model and the related experiments were validated. Furthermore, as a new analysis indicator, saturation percentage was introduced first. The experimental results indicate that the revised flow area model is more accurate compared to the original one, and vibration waveforms can be optimized through suitable spool parameters and the revised cylinder structure.

The possibility of applying a high-pressure hydro-jet for renewal of the grinding wheel cutting ability was presented. This work was conducted in the internal cylindrical grinding process of the Titanium Grade 2^® alloy, which belongs to the group of hard-to-cut materials. The analysis shows that the impact on the erosion effectiveness of the grinding wheel active surface (GWAS) depends upon the hydro-jet inclination angle and working pressure. Experimental results reveal that application of hydro-jet working pressure of 25 MPa allows for effective cleansing of the grinding wheel surface. Depending on the initial GWAS condition and the level of its smearing with chips of machined material, it is possible to increase the number of grinding wheel unevenness apexes by as much as 4.5 times.

After analyzing the working condition of the conventional diesel forklift, an energy recovery system in hybrid forklift is considered and its simulation model is built. Then, the control strategy for the proposed energy recovery system is discussed, which is validated and evaluated by simulation. The simulation results show that the proposed control strategy can achieve balance of the power and keep the state of charge (SOC) of ultra capacitor in a reasonable range, and the fuel consumption can be reduced by about 20.8% compared with the conventional diesel forklift. Finally, the feasibility of the simulation results is experimentally verified based on the lifting energy recovery system.

For multiple grid-connected inverters with active filter function, it makes sense to regulate every unit to output maximum active power from photovoltaic arrays, as well as eliminate the harmonic due to the non-linear loads connected to the electric networks. Naturally, a centralized control coordination strategy was proposed for the purpose of high facility utilization, good harmonic compensation ability and unwanted overcompensation condition. Based on a vector decoupling control scheme and generalized instantaneous reactive power theory, the solution was to allocate the harmonic eliminating task for every inverter according to the instantaneous power margin of each. The grid current always keeps sinusoidal in spite of non-linear load change and output active power change for any inverter. The simulation results validate the efficacy of the proposed coordination strategy.

Electrophoretic display (EPD) technology has become one of the main supporting pillars of the electronic paper display industry. Despite its benefits, the EPD technology suffers from several disadvantages such as non-fixed threshold voltage value for gray scale display. In addition, the display has to repeatedly refresh between white and black states to eliminate ghost image when it needs to update a new image. The traditional driving waveform for the EPD includes four stages: erasing the original image, resetting to black state, clearing to white state, and writing a new image. A flicker can be found when transferring between two adjacent stages. A new driving waveform based on the improvement of activation pattern is proposed to weaken the ghost image and reduce the flicker. Experimental results show that the proposed driving waveform could weaken the ghost image effectively and reduce the number of flickers by 50%. Compared with the traditional driving waveform, the driving waveform of this work has a better performance.

Heterogeneous wireless access technologies will coexist in next generation wireless networks. These technologies form integrated networks, and these networks support multiple services with high quality level. Various access technologies allow users to select the best available access network to meet the requirements of each type of communication service. Being always best connected anytime and anywhere is a major concern in a heterogeneous wireless networks environment. Always best connected enables network selection mechanisms to keep mobile users always connected to the best network. We present an overview of the network selection and prediction problems and challenges. In addition, we discuss a comprehensive classification of related theoretic approaches, and also study the integration between these methods, finding the best solution of network selection and prediction problems. The optimal solution can fulfill the requirements of the next generation wireless networks.

Privacy is becoming one of the most notable challenges threatening wireless sensor networks (WSNs). Adversaries may use RF (radio frequency) localization techniques to perform hop-by-hop trace back to the source sensor’s location. A multiple k-hop clusters based routing strategy (MHCR) is proposed to preserve source-location privacy as well as enhance energy efficiency for WSNs. Owing to the inherent characteristics of intra-cluster data aggregation, each sensor of the interference clusters is able to act as a fake source to confuse the adversary. Moreover, dummy traffic could be filtered efficiently by the cluster heads during the data aggregation, ensuring no energy consumption be burdened in the hotspot of the network. Through careful analysis and calculation on the distribution and the number of interference clusters, energy efficiency is significantly enhanced without reducing the network lifetime. Finally, the security and delay performance of MHCR scheme are theoretically analyzed. Extensive analysis and simulation results demonstrate that MHCR scheme can improve both the location privacy security and energy efficiency markedly, especially in large-scale WSNs.

Two-tier heterogeneous networks (HetNets), where the current cellular networks, i.e., macrocells, are overlapped with a large number of randomly distributed femtocells, can potentially bring significant benefits to spectral utilization and system capacity. The interference management and access control for open and closed femtocells in two-tier HetNets were focused. The contributions consist of two parts. Firstly, in order to reduce the uplink interference caused by MUEs (macrocell user equipments) at closed femtocells, an incentive mechanism to implement interference mitigation was proposed. It encourages femtocells that work with closed-subscriber-group (CSG) to allow the interfering MUEs access in but only via uplink, which can reduce the interference significantly and also benefit the marco-tier. The interference issue was then studied in open-subscriber-group (OSG) femtocells from the perspective of handover and mobility prediction. Inbound handover provides an alternative solution for open femtocells when interference turns up, while this accompanies with PCI (physical cell identity) confusion during inbound handover. To reduce the PCI confusion, a dynamic PCI allocation scheme was proposed, by which the high handin femtocells have the dedicated PCI while the others share the reuse PCIs. A Markov chain based mobility prediction algorithm was designed to decide whether the femtocell status is with high handover requests. Numerical analysis reveals that the UL interference is managed well for the CSG femtocell and the PCI confusion issue is mitigated greatly in OSG femtocell compared to the conventional approaches.

Recent researches show that inter-session network coding could decrease the number of packets transmission and achieve higher throughput in wireless network compared with traditional forwarding mechanism. In most existing relay mechanisms based on inter-session network such as COPE, relay node demands to collect the messages from its neighbor nodes to get notice of which packets already overheard by them so as to determine whether there exists coding opportunity between or among forwarding packets. However, transmission overhead of this message collection and computing cost of opportunity determination will degrade the performance of these mechanisms. It is observed that coding opportunity at relay node is much more related with the local topology, and the opportunity of encoding three or more packets together is far less than that of encoding two packets together in wireless network with general density. Based on this, a new coding-aware routing mechanism, named TCAR, is proposed. TCAR ignores the opportunity of encoding three or more than three packets together. Each relay node maintains an encoding mapping table being established according to the result of its local topology detection, which can be used to calculate the path cost during routing setup phase, and determine that which two packets can be encoded together during the packets forwarding phase. In TCAR, instead of periodic messages collection, each relay nodes just need once local topology detection, and the encoding determination is much simpler than that of the former mechanisms. Simulation results show that compared with typical inter-session network coding mechanisms COPE and COPE-based routing, TCAR achieves 12% and 7% throughput gains, and keeps the minimum end to end delay.

Private clouds and public clouds are turning mutually into the open integrated cloud computing environment, which can aggregate and utilize WAN and LAN networks computing, storage, information and other hardware and software resources sufficiently, but also bring a series of security, reliability and credibility problems. To solve these problems, a novel secure-agent-based trustworthy virtual private cloud model named SATVPC was proposed for the integrated and open cloud computing environment. Through the introduction of secure-agent technology, SATVPC provides an independent, safe and trustworthy computing virtual private platform for multi-tenant systems. In order to meet the needs of the credibility of SATVPC and mandate the trust relationship between each task execution agent and task executor node suitable for their security policies, a new dynamic composite credibility evaluation mechanism was presented, including the credit index computing algorithm and the credibility differentiation strategy. The experimental system shows that SATVPC and the credibility evaluation mechanism can ensure the security of open computing environments with feasibility. Experimental results and performance analysis also show that the credit indexes computing algorithm can evaluate the credibilities of task execution agents and task executor nodes quantitatively, correctly and operationally.

Constrained optimization problems are very important as they are encountered in many science and engineering applications. As a novel evolutionary computation technique, cuckoo search (CS) algorithm has attracted much attention and wide applications, owing to its easy implementation and quick convergence. A hybrid cuckoo pattern search algorithm (HCPS) with feasibility-based rule is proposed for solving constrained numerical and engineering design optimization problems. This algorithm can combine the stochastic exploration of the cuckoo search algorithm and the exploitation capability of the pattern search method. Simulation and comparisons based on several well-known benchmark test functions and structural design optimization problems demonstrate the effectiveness, efficiency and robustness of the proposed HCPS algorithm.

A service life model of NAND flash and threshold voltage shift process is proposed to calculate the service life and endurance. The relationships among achievable program/erase (P/E) cycles, recovery time, bad block rate and storage time are analyzed. The achievable endurance and service life of a NAND flash are evaluated based on a flash cell degradation and recovery model by varying recovery time, badblock rate, and storage time. It is proposed to improve the service lifetime of solid state disk by both relaxing the bad block rate limitation and retention time while extending the recovery time. The results indicate that endurance can be improved by 17 times if the storage time guarantee is reduced from 10 a to 1 a with 10⁵ s recovery time inserted between cycles.

A new solar coupling regeneration system is proposed in order to improve the reliability of solar desiccant regeneration system. The new system makes comprehensively use of the solar energy and can also be appropriate for energy-storage in a night operation mode when the electric power supply is at its valley. Comparison of the performance of the new system, the solar thermal regeneration system and the solar electrodialysis regeneration system are made and the influential factors of the performance of the new system are investigated. The results reveal that the new system will be more energy efficient than the solar thermal regeneration system and the solar electrodialysis regeneration system.

Water shutoff through injection wells is one of the most important techniques used for water injection profile control and modification in severely heterogeneous reservoirs, aiming at stabilizing oil production. It has been widely reported that the effectiveness and efficiency of water shutoff using gel is mostly dependent on the gel dynamic sealing properties in the porous media. Firstly the gelation strength and gelation time of polymer gel were evaluated. Then, core flowing experiments were conducted before and after gelation in a 32 m long sand pack. In addition, water flooding core experiments were also carried out in a long core of 80 cm before and after injecting gel system to check the reliability of this evaluation method. The experimental results show that moderate-strength gel can be formed at 65 °C. According to the integrated evaluation of the plugging coefficient, plugging strength and water breakthrough time, the gel particles are capable of migrating to a distance of 7.47 m from the injection point of the 32 m long sand pack during the water injection process after gelation. Based on sands gelation status and effluent analyses, the effective migration distance of the gel particles is 4–14 m. Through the core flooding experiments using the 80 cm heterogeneous core, it is evidenced that the gel can be formed in the deep reservoir (40.63% of total length) with the plugging strength as high as 6.33 MPa/m, which leads to extra oil recovery of 10.55% of original oil in place (OOIP) by water flooding after gel treatment.

The technology that waste activated carbon after extracting gold is regenerated with steam under microwave heating was studied. The influence of the activation temperature, activation duration and steam flow rate on iodine adsorption value and regeneration yield of activated carbon was investigated. The response surface methodology (RSM) technique was utilized to optimize the process conditions. The optimum conditions for the preparation of activated carbon are identified to be activation temperature of 831 °C, activation duration of 40 min and steam flow rate of 2.67 mL/min. The optimum conditions result in an activated carbon with an iodine number of 1048 mg/g and a yield of 40%, and the BET surface area evaluated using nitrogen adsorption isotherm is 1493 m²/g, with total pore volume of 1.242 cm³/g. And the pore structure of activated carbon regenerated is mainly composed of micropores and a small amount of mesopores.

Pickling sludge generated during the neutralization of pickling wastewater with calcium hydroxide in stainless steel pickling process was characterized using X-ray fluorescence spectrometry, X-ray diffractometry, scanning electron microscopy, thermogravimetry and differential scanning calorimetry, etc. The major compositions of pickling sludge are CaF₂, CaSO₄, Me(OH)_n (M: Fe, Cr, Ni), and the content of CaF₂ is high in the sludge. The melting point of pickling sludge is about 1350 °C and the viscosity is about 0.14 Pa·s at 1450 °C, which are comparatively lower than those of normal refining slag. After heat treatment, the contents of sulfur and fluorine in the pickling sludge were reduced, confirming the thermal decomposition of sulfate in the sludge. Fluorine in the sludge is reduced by the gaseous SiF₄ and AlF₃ generated through the reactions of CaF₂ with SiO₂ and Al₂O₃. The preliminary results from the reduction test indicate that the sulfur content in the steel is not affected by the presence of sulfur in the sludge. The recovery of nickel is about 40%, and the chromium content changes marginally due to the protective atmosphere under the reduction condition of chromic oxide. The pickling sludge is a potential auxiliary material for the production of stainless steel.

Combined with the kinetic model of liquid film spreading, a new numerical method of solid-liquid-gas three-phase flow was developed for the moving of contact line, which was a hybrid method of computational fluid dynamics and lattice Boltzmann method (LBM). By taking the effect of molecule force in droplet and the wall surface on liquid film into account, the changing law of contact angle with different surface tensions was analyzed on glass and aluminum foil surfaces. Compared with experimental results, the standard deviation by using LBM is less than 0.5°, which validates the feasibility of LBM simulation on the dynamic process of liquid film spreading. In addition, oscillations are discovered both at the initial and end phases. The phenomenon of retraction is also found and the maximum retraction angle is 7.58°. The obtained result shows that the retraction is proved to be correlative with precursor film by tracking the volume change of liquid film contour. Furthermore, non-dimensional coefficient λ is introduced to measure the liquid film retraction capacity.

In order to improve the efficiency of bioleaching heavy metal from the contaminated soil using Penicillium chrysogenum (P. chrysogenum), experiment was conducted to evaluate the influence of heavy metal stress on P. chrysogenum during bioleaching. The morphology and physiology of P. chrysogenum were observed. Assuming that the heavy metals are all leached out from the experiment soil, heavy metals are added into the agar medium by simulating the heavy metal content in the soil. It is concluded that the survivable heavy metal contaminated soil mass range for P. chrysogenum is 2.5–5.0 g. As for biomass determination, the contaminated soil is added into the liquid medium directly. The soil mass that P. chrysogenum can be survivable is in the range of 2.5–8.75 g. In this mass range, the biomass of P. chrysogenum is bigger than that of the control sample. 10 g soil mass is the threshold of the growth of P. chrysogenum. 102.2 mg/L gluconic acid, 156.4 mg/L oxalic acid, 191.6 mg/L pyruvic acid, 0.02 mg/L citric acid, 0.03 mg/L malic acid and 70.6 mg/L succinic acid are determined after 15 d bioleaching. The mycelium is broken into fragments, and heavy metals are adsorbed on the cell wall or transported into the cytoplasm during bioleaching. The GOD activity declines from 1.08 U/mL to 0.2 U/mL under 400 mg/L of multi-metal stress. The influence of Pb on GOD activity is bigger than that of Cr and Cd, and the GOD activity is not influenced apparently by Mn, Zn and Cu.

A series of marine natural gas fields were recently discovered in oolitic dolomites of the Lower Triassic Feixianguan formation, northeastern Sichuan Basin, southwest China. The mechanism forming these reservoir dolomites is debatable, limiting the ability to characterize these reservoir successfully. Based on the investigation of the representative Dukouhe, Luojiazhai, and Puguang areas, this issue was addressed by examining the distribution, petrology, and geochemistry of the dolomites, the most comprehensive study to date was provided. Dolomitization occurred at a very early stage of diagenesis, as shown by the petrological features of the rock fabric. Vadose silt, which is composed primarily of dolomitic clasts, is found in the primary and secondary pores of the oolitic dolomite. This indicates that the overlying strata were subjected to dolomitization when the Feixianguan formation was located in the vadose zone. Therefore, it may be inferred that the dolomitization which occurred before the formation was exposed to meteoric conditions. The spatial distribution and geochemical characteristics of the dolomite indicate that dolomitization occurred as a result of seepage reflux. The degree of dolomitization decreases with increasing distance from the evaporative lagoon. Furthermore, the type and porosity of the dolomite vary in different zones of the upward-shoaling sequence, with the porosity gradually decreasing from the highest layer to the lowest layer. This reflects a close relationship between dolomitization and seawater evaporation during the formation of the dolomite. Geochemical analysis provided further evidence for the relationship between the dolomitization fluid and the coeval seawater. The ⁸⁷Sr/⁸⁶Sr and δ¹³C isotopes, as well as the abundances of trace elements, Fe and Mn, indicate that seawater concentrated by evaporation acted as the dolomitization fluid. These results also show that dolomitization most likely occurred in a semi-closed diagenetic environment. Therefore, the main mechanism of oolitic dolomite formation is seepage reflux, which occurred at an early stage of diagenesis.

Based on some assumptions, the dynamic governing equation of anchorage system is established. The calculation formula of natural frequency and the corresponding vibration mode are deduced. Besides, the feasibility of the theoretical method is verified by using a specific example combined with other methods. It is found that the low-order natural frequency corresponds to the first mode of vibration, and the high-order natural frequency corresponds to the second mode of vibration, while the third mode happens only when the physical and mechanical parameters of anchorage system meet certain conditions. With the increasing of the order of natural frequency, the influence on the dynamic mechanical response of anchorage system decreases gradually. Additionally, a calculating method, which can find the dangerous area of anchorage engineering in different construction sites and avoid the unreasonable design of anchor that may cause resonance, is proposed to meet the seismic precautionary requirements. This method is verified to be feasible and effective by being applied to an actual project. The study of basic dynamic features of anchorage system can provide a theoretical guidance for anchor seismic design and fast evaluation of anchor design scheme.

The boundary between the near and far fields is generally defined as the distance from the vibration source beyond which ground vibrations are mainly dominated by Rayleigh waves. It is closely related to the type of vibration source and the soil properties. Based on the solutions of the Lamb’s problem, the boundary at the surface between the near and far fields of ground vibration was investigated for a harmonic vertical concentrated load and an infinite line load at the surface of a visco-elastic half-space. Particularly, the variation of the boundary with the material damping was investigated for both cases. The results indicate that the material damping slightly contributes to the attenuation of vibrations in the near-source region, but significantly reduces the vibrations in the region that is at some distance away from the source. When taking the material damping into consideration, the boundary between the near and far fields tends to move towards the vibration source. Compared with the vibrations caused by a concentrated load, the vibrations induced by an infinite line load can affect a larger range of the surrounding environment, and they attenuate more slowly. This means the boundary between the near field and far field should move further away from the source. Finally, the boundaries are defined in terms of R-wave length (λ_R) and Poisson ratio of the ground (gv). For the case of a point load, the boundary is located at the distance of (5.0–6.0)λ_R for gv≤0.30 and at the distance of (2.0–3.0)λ_R for gv≥0.35. For the case of an infinite line load, the boundary is located at the distance (5.5–6.5)λ_R for gv≤0.30 and at the distance (2.5–3.5)λ_R for gv≥0.35.

The variance-dependent Goldstein radar interferogram filter takes into account the information of both interferometric coherence and multilook factors, and can produce very consistent results for interferograms generated under a wide variety of multilook factors and with very different noise level. However, the filter is a bit complicated and its application is still very limited. We present the designing and implementation of the variance-dependent Goldstein radar interferogram filtering, emphasizing on the logic flow, the generation of look-up table, the determination of filtering parameter, and the handling of edge information loss. Experiments with real interferograms are provided to demonstrate the applications of the designed filtering. Comparisons with the result of the coherence-dependent Goldstein filter show that improvements from 18.4% to 36.9% are achieved when the variance-dependent filter is used, and the noisier the interferogram, the greater the improvement.

Based on the simplification of cutting process, a series of numerical simulations were conducted using a 2-D discrete element method to explore the effects of embedded cracks with different dip angles on the rock fragmentation process, cutting characteristics and breaking efficiency. The results show that the simulated results are in a good agreement with previous theoretical study. The main crack propagates to the top tip of embedded crack, except when the dip angle is 90°. Side cracks which are more fully developed in the rocks containing embedded cracks tend to propagate towards the free surface. According to the history of vertical cutting force, it is shown that the peak force is decreased by embedded cracks. The study on cutting efficiency was conducted by combining the quantity of crack and cutting energy. And the results show that breaking efficiency can be treated as a decreasing or a increasing function when the dip angle is less or larger than 30°, respectively. Breaking efficiency is higher than that in intact rock when the dip angle is larger than 45°.

A probabilistic method based on principle of maximum entropy was employed to analyze the randomness of contact force between geomembrane and granular material. The contact force distribution is exponential according to the proposed method and the grain size is the most important factor that affects the distribution of contact force. The proposed method is then verified by a series of laboratory experiments using glass beads and cobbles as granular material and a very thin pressure, indicating that film is firstly used in these experiments which give a reliable method to measure the contact force at each contact point.

Multi-stage triaxial compression tests for cylindrical red sandstone specimens (diameter of 50 mm, height of 100 mm) were carried out with a rock mechanics testing system and spatial acoustic emission (AE) locations were obtained by adopting an AE monitoring system. Based on spatial AE distribution evolution of red sandstone during multi-stage triaxial deformation, the relation between spatial AE events and triaxial deformation of red sandstone was analyzed. The results show that before peak strength, the spatial AE events are not active and distribute stochastically in the specimen, while after peak strength, the spatial AE events are very active and focus on a local region beyond final microscopic failure plane. During multi-stage triaxial deformation with five different confining pressures, the spatial AE distribution evolution in the red sandstone was obtained. The obtained spatial AE locations of red sandstone at the final confining pressure agree very well with the ultimate failure experimental mode. Finally, the influence of confining pressure on the spatial AE evolution characteristics of red sandstone during triaxial deformation was discussed. The AE behavior of red sandstone during multi-stage triaxial deformation is interpreted in the light of the Kaiser effect, which has a significant meaning for predicting the unstable failure of engineering rock mass.

Considering the viscous damping of the soil and soil-pile vertical coupled vibration, a computational model of large-diameter pipe pile in layered soil was established. The analytical solution in frequency domain was derived by Laplace transformation method. The responses in time domain were obtained by inverse Fourier transformation. The results of the analytical solution proposed agree well with the solutions in homogenous soil. The effects of the shear modulus and damping coefficients of the soil at both outer and inner sides of the pipe pile were researched. The results indicate that the shear modulus of the outer soil has more influence on velocity admittance than the inner soil. The smaller the shear modulus, the larger the amplitude of velocity admittance. The velocity admittance weakened by the damping of the outer soil is more obvious than that weakened by the damping of the inner soil. The displacements of the piles with the same damping coefficients of the outer soil have less difference. Moreover, the effects of the distribution of soil layers are analyzed. The results indicate that the effect of the upper soil layer on dynamic response of the pipe pile is more obvious than that of the bottom soil layer. A larger damping coefficient of the upper layer results in a smaller velocity admittance. The dynamic response of the pipe pile in layered soil is close to that of the pipe pile in homogenous soil when the properties of the upper soil layer are the same.

Room and pillar sizes are key factors for safe mining and ore recovery in open-stope mining. To investigate the influence of room and pillar configurations on stope stability in highly fractured and weakened areas, an orthogonal design with two factors, three levels and nine runs was proposed, followed by three-dimensional numerical simulation using ANSYS and FLAC^3D. Results show that surface settlement after excavation is concentrically ringed, and increases with the decrease of pillar width and distances to stope gobs. In the meantime, the ore-control fault at the ore-rock boundary and the fractured argillaceous dolomite with intercalated slate at the hanging wall deteriorate the roof settlement. Additionally, stope stability is challenged due to pillar rheological yield and stress concentration, and both are induced by redistribution of stress and plastic zones after mining. Following an objective function and a constraint function, room and pillar configuration with widths of 14 m and 16 m, respectively, is presented as the optimization for improving the ore recovery rate while maintaining a safe working environment.

Based on transient temperature field theory of heat conduction, the solar temperature field calculation model of U-shape sectioned high-speed railway cable-stayed bridge under actions of concrete beams and ballast was established. Using parametric programming language, finite element calculation modules considering climate conditions, bridge site, structure dimension and material thermophysical properties were compiled. Six standard day cycles with the strongest yearly radiation among the bridge sites were selected for sectional solar temperature field calculation and temperature distributions under different temperature-sensitive parameters were compared. The results show that under the influence of sunshine, U-shape section of the beam shows obvious nonlinear distribution characteristics and the maximum cross-section temperature difference is more than 21 °C; the ballast significantly reduces sunshine temperature difference of the beam and temperature peak of the bottom margin lags with the increase of ballast thickness; the maximum cross-section vertical temperature gradient appears in summer while large transverse temperature difference appears in winter.

Pantograph-catenary contact force provides the main basis for evaluation of current quality collection; however, the pantograph-catenary contact force is largely affected by the catenary irregularities. To analyze the correlated relationship between catenary irregularities and pantograph-catenary contact force, a method based on nonlinear auto-regressive with exogenous input (NARX) neural networks was developed. First, to collect the test data of catenary irregularities and contact force, the pantograph/catenary dynamics model was established and dynamic simulation was conducted using MATLAB/Simulink. Second, catenary irregularities were used as the input to NARX neural network and the contact force was determined as output of the NARX neural network, in which the neural network was trained by an improved training mechanism based on the regularization algorithm. The simulation results show that the testing error and correlation coefficient are 0.1100 and 0.8029, respectively, and the prediction accuracy is satisfactory. And the comparisons with other algorithms indicate the validity and superiority of the proposed approach.

The improved granular mixtures are widely used as the fillings of railway subgrade, and in order to investigate the effect of coarse grain content on granular mixtures, a series of field tests were conducted. The experimental results indicate that the permeability coefficient increases significantly with the increment of granite gravel content, especially in the range of 60%–70%. There exists a coarse grain content limit defined as 53%–58.5% to reform the permeable granular skeleton. Beyond this limit, the permeable granular skeleton is efficiently formed, and the macro pores between the separate gravels are partially filled, which is the explanation for the permeability increase. The investigations indicate the subgrade resistance modulus (k₃₀, E_v2, and E_vd) depends on the granite gravel content, and the resistance modulus increases significantly beyond granite gravel content of 50%. The skeletons of granite gravel-clayey sand mixture change in the long-term deformation objected to the train-induced dynamic load, which involves three main repeated and circular deformation stages. Generally, the long-time deformation is explained as the gravel crushing and filling the internal porous space with crushed gravel fragments. Through these investigations, the C40–G60 or C30–G70 is recommended as an optimum soil mixture for the good permeability and high resistance modulus.

In order to study the sliding characteristics when the cable is connected with the other rods in the transmission line structures, a linear sliding cable element based on updated Lagrangian formulation and a sliding catenary element considering the out-of-plane stiffness coefficient are put forward. A two-span and a three-span cable structures are taken as examples to verify the sliding cable elements. By comparing the tensions of the two proposed cable elements with the existing research results, the error is less than 1%, which proves the correctness of the proposed elements. The sliding characteristics should be considered in the practical engineering because of the significant difference between the tensions of sliding cable elements and those of cable element without considering sliding. The out-of-plane stiffness coefficient and friction characteristics do not obviously affect the cable tensions.

In recent years, there have been important developments in the joint analysis of the travel behavior based on discrete choice models as well as in the formulation of increasingly flexible closed-form models belonging to the generalized extreme value class. The objective of this work is to describe the simultaneous choice of shopping destination and travel-to-shop mode in downtown area by making use of the cross-nested logit (CNL) structure that allows for potential spatial correlation. The analysis uses data collected in the downtown areas of Maryland-Washington, D.C. region for shopping trips, considering household, individual, land use, and travel-related characteristics. The estimation results show that the dissimilarity parameter in the CNL model is 0.37 and significant at the 95% level, indicating that the alternatives have high spatial correlation for the short shopping distance. The results of analysis reveal detailed significant influences on travel behavior of joint choice shopping destination and travel mode. Moreover, a Monte Carlo simulation for a group of scenarios arising from transportation policies and parking fees in downtown area, was undertaken to examine the impact of a change in car travel cost on the shopping destination and travel mode switching. These findings have important implications for transportation demand management and urban planning.

The optimization of high density and concentrated-weight freights loading requires an even distribution of the freight’s weight and unconcentrated loading on the floor of the car. Based on the characteristics of concentrated-weight category freights, an improvement method is put forward to build freight towers and a greedy-construction algorithm is utilized based on heuristic information for the initial layout. Then a feasibility analysis is performed to judge if the balanced and unconcentrated loading constrains are reached. Through introducing optimization or adjustment methods, an overall optimal solution can be obtained. Experiments are conducted using data generated from real cases showing the effectiveness of our approach: volume utility ratio of 90.4% and load capacity utility ratio of 86.7% which is comparably even to the packing of the general freights.

Bicycle-sharing system is considered as a green option to provide a better connection between scenic spots and nearby metro/bus stations. Allocating and optimizing the layout of bicycle-sharing system inside the scenic spot and around its influencing area are focused on. It is found that the terrain, land use, nearby transport network and scenery point distribution have significant impact on the allocation of bicycle-sharing system. While the candidate bicycle-sharing stations installed at the inner scenic points, entrances/exits and metro stations are fixed, the ones installed at bus-stations and other passenger concentration buildings are adjustable. Aiming at minimizing the total cycling distance and overlapping rate, an optimization model is proposed and solved based on the idea of cluster concept and greedy heuristic. A revealed preference/stated preference (RP/SP) combined survey was conducted at Xuanwu Lake in Nanjing, China, to get an insight into the touring trip characteristics and bicycle-sharing tendency. The results reveal that 39.81% visitors accept a cycling distance of 1–3 km and 62.50% respondents think that the bicycle-sharing system should charge an appropriate fee. The survey indicates that there is high possibility to carry out a bicycle-sharing system at Xuanwu Lake. Optimizing the allocation problem cluster by cluster rather than using an exhaustive search method significantly reduces the computing amount from O(2⁴³) to O(43²). The 500 m-radius-coverage rate for the alternative optimized by 500 m-radius-cluster and 800 m-radius-cluster is 89.2% and 68.5%, respectively. The final layout scheme will provide decision makers engineering guidelines and theoretical support.