Showing papers in "Journal of Central South University of Technology in 2008"

Preparation of fluorescence starch-nanoparticle and its application as plant transgenic vehicle

Abstract: Starch-nanoparticles were synthesized in water-in-oil microemusion at room temperature, and the starch-nanoparticles were coated with poly-L-lysine The surface of the starch-nanoparticles was combined with fluorescence material Ru(bpy)32+·6H2O, and then the particles were characterized via transmission electron microscope The fluorescence nanoparticles were conjugated with plasmid DNA to form complexes, and then treated with ultrasound and DNase I pEGAD plasmid DNA-nanoparticle complexes were co-cultured with plant suspension cells of Dioscrea Zigiberensis G H Wright, and treated with ultrasound The results show that the diameter of the fluorescence starch-nanoparticles is 50–100 nm DNA-nanoparticle complexes can protect DNA from ultrasound damage as well as from DNase I cleavage Mediated by ultrasound, pEGAD plasmid DNA-nanoparticle complexes can pierce into the cell wall, cell membrane and nucleus membrane of plant suspension cells The green fluorescence protein(GFP) gene at a high frequency exceeds 5% This nano-biomaterial can efficiently solve the problem that exterior genes cannot traverse the plant cell wall easily

Numerical analyses of influence of overlying pit excavation on existing tunnels

Abstract: The response of existing tunnel due to overlying excavation was studied using 2D FEM (Finite element method). Three typical locations of tunnel with respect to excavation, namely at the central line under the excavation bottom, directly under the base of diaphragm wall and outside of diaphragm, were considered. The variation of tunnel response with the change of location of tunnel was analyzed. The stress path of soil surrounding tunnel during the process of excavation was compared. Numerical analysis results indicate that the underlying tunnels at different locations under the excavation will experience convergence and divergence due to overlying excavation. Moreover, the tunnel located below base of diaphragm wall will experience distortion. The deformation is mainly due to the uneven changes of ground contact pressure on tunnel linings. Both the vertical and horizontal displacement of the tunnel decrease with the increase of the tunnel embedded depth beneath the formation of excavation.

Evaluation of statistical strength of bamboo fiber and mechanical properties of fiber reinforced green composites

Abstract: Green composites made from bamboo fibers and biodegradable resins were fabricated with press molding. On the basis of the Weibull distribution and the weakest-link theory, the statistical strength and distribution of bamboo fiber were analyzed, and the tensile strength of green composites was also investigated. The result confirms that the tensile statistical strength of fiber fits well with two-parameter Weibull distribution. In addition, the tensile strength of bamboo fiber reinforced composites is about 330 MPa with the fiber volume fraction of 70%. This value is close to or higher than that of other natural fiber reinforced green composites.

Leaching kinetics of low grade zinc oxide ore in NH3-NH4Cl-H2O system

Abstract: The leaching kinetics of low grade zinc oxide ore in NH3-NH4Cl-H2O system was studied. The effects of ore particle size, reaction temperature and the sum concentration of ammonium ion and ammonia on the leaching efficiency of zinc were examined. The leaching kinetics of low-grade zinc oxide ore in NH3-NY4Cl-H2O system follows the kinetic law of shrinking-core model. The results show that diffusion through the inert particle pores is the leaching kinetics rate controlling step. The calculated apparent activation energy of the process is about 7.057 kJ/mol. The leaching efficiency of zinc is 92.1% under the conditions of ore particle size of 69 μm, holding at 80 °C for 60 min, sum ammonia concentration of 7.5 mol/L, the molar ratio of ammonium to ammonia being 2:1, and the ratio (g/mL) of solid to liquid being 1:10.

Displacement of polymer solution on residual oil trapped in dead ends

Abstract: For waterflooding reservoir, oil trapped in pore’s dead ends is hardly flushed out, and usually becomes one typical type of residual oil. The microscopic displacement characteristics of polymer solution with varied viscoelastic property were studied by numerical and experimental method. According to main pore structure characteristics and rheological property of polymer solution through porous media, displacement models for residual oil trapped in dead ends were proposed, and upper-convected Maxwell rheological model was used as polymer solution’s constitutive equation. The flow and stress field was given and displacement characteristic was quantified by introducing a parameter of micro swept coefficient. The calculated and experimental results show that micro swept coefficient rises with the increase of viscoelasticity; for greater viscoelasticity of polymer solution, vortices in the dead end have greater swept volume and displacing force on oil, and consequently entraining the swept oil in time. In addition, micro swept coefficient in dead end is function of the inclination angle (θ) between pore and dead end. The smaller of θ and 180-θ, the flow field of viscoelastic fluid is developed in dead ends more deeply, resulting in more contact with oil and larger swept coefficient.

Structure characterization and electrochemical properties of new lithium salt LiODFB for electrolyte of lithium ion batteries

Abstract: Lithium difluoro(axalato)borate (LiODFB) was synthesized in dimethyl carbonate (DMC) solvent and purified by the method of solventing-out crystallization. The structure characterization of the purified LiODFB was performed by Fourier transform infrared (FTIR) spectrometry and nuclear magnetic resonance (NMR) spectrometry. The electrochemical properties of the cells using 1 mol/L LiPF6 and 1 mol/L LiODFB in ethylene carbonate (EC)/DMC were investigated, respectively. The results indicate that LiODFB can be reduced at about 1.5 V and form a robust protective solid electrolyte interface (SEI) film on the graphite surface in the first cycle. The graphite/LiNi1/3Mn1/3Co1/3O2 cells with LiODFB-based electrolyte have very good capacity retention at 55 °C, and show very good rate capability at 0.5C and 1C charge/discharge rate. Therefore, as a new salt, LiODFB is a most promising alternative lithium salt to replace LiPF6 for lithium ion battery electrolytes in the future.

Rheological properties of oil-based drilling fluids at high temperature and high pressure

Abstract: The rheological properties of two kinds of oil-based drilling fluids with typically composition were studied at pressures up to 138 MPa and temperatures up to 204 °C using the RheoChan 7400 Rheometer. The experimental results show that the apparent viscosity, plastic viscosity and yield point decrease with the increase of temperature, and increase with the increase of pressure. The effect of pressure on the apparent viscosity, plastic viscosity and yield point is considerable at ambient temperature. However, this effect gradually reduces with the increase of temperature. The major factor influencing the rheological properties of oil-based drilling fluids is temperature instead of pressure in the deep sections of oil wells. On the basis of numerous experiments, the model for predict the apparent viscosity, plastic viscosity and yield point of oil-based drilling fluids at high temperature and pressure was established using the method of regressive analysis. It is confirmed that the calculated data are in good agreement with the measured data, and the correlation coefficients are more than 0.98. The model is convenient for use and suitable for the application in drilling operations.

FTIR analysis of adsorption of poly diallyl-dimethyl-ammonium chloride on kaolinite

Abstract: The flocculation behavior of ultrafine kaolinite suspension was investigated through settlement tests and FTIR method was employed to probe the adsorption mechanism of flocculant on kaolinite. The results show that the maximum settling rate of kaolinite occurs at pH value of 3.33, which is close to the point of zero charge(PZC) of kaolinite (3.5). This result is in good agreement with the double electric layer theory. Kaolinite suspension reaches the largest settling rate at a low concentration of 39 g/t for poly diallyl-dimethyl-ammonium chloride(PDADMA) flocculant, whereas for polyacrylamides(PAM) the dosage is required to be 500 g/t. When macromolecule polymer is adsorbed on surface, kaolinite particles may be flocculant due to the bridging effect. There are cation flocculant characteristic bands on the spectrum of kaolinite but no obvious shifting. Thus, the adsorption of poly diallyl-dimethyl-ammonium chloride on kaolinite surface is physical adsorption.

VCR and ASR technology for profile and flatness control in hot strip mills

Abstract: The roll contour pattern and variety of work and backup rolls in service and its effect on profile and flatness control performance in 1 700 mm hot strip mill at Wuhan Iron and Steel (Group) Corporation were tested and analyzed by the developed finite element models of different typical roll contours configurations. A rather smooth local work roll contour near strip edges and an increase in rolled length can be obtained by application of long stroke work roll shifting system with conventional work roll contours that is incapable of the crown control. In comparison with the conventional backup and work roll contours configuration, the crown control range by the roll bending force enhances by 12.79% and the roll gap stiffness increases by 25.26% with the developed asymmetry self-compensating work rolls(ASR) and varying contact backup rolls(VCR). A better strip profile and flatness quality, an increase in coil numbers within the rolling campaign and a significant alleviated effect of severe work roll wear contours on performance of edge drop control are achieved by the application of ASR with crown control and wear control ability in downstream stand F5 and VCR in all stands of 1 700 mm hot strip mill.

Experimental evaluation on high temperature rheological properties of various fiber modified asphalt binders

Abstract: High temperature rheological properties of fiber modified asphalt binders and impact of the type and content on such properties were studied. Three types of fiber, including polyester (PET), polyacrylonitrile (PAN) and cellulose (CEL), a control content (0%) and four levels of fiber content (2%, 4%, 6% and 8% by total asphalt binder mass) were used with asphalt binders. The high temperature rheological properties, consisting of complex modulus (G*) and phase angle δ, were measured using SHRP’s dynamic shear rheometer (DSR) between 46–82 °C. Experimental results indicate that the changes of G* and tan δ of fiber modified asphalt binders with the increase of test temperature tend to slow down, and the temperature susceptibility is improved obviously compared to that of original asphalt binder. Fiber modification results in the increase of rutting parameter (G*/sin δ) at high temperatures, the decrease of temperature susceptibility, and further improved high temperature performance of asphalt binder. An excellent correlation exhibits between fiber content and high temperature performance of asphalt binder. Moreover, fiber type also has different influences on the improvement of G*/sin δ, G*/sin δ of PET and PAN fiber asphalt binders are both higher than that of CEL fiber, but G*/sin δ of CEL fiber is still higher than that of original asphalt. However, there is a critical fiber content when fibers start to interact with each other. Therefore, based on the critical fiber content and economic consideration, the optimum fiber contents for various fiber-modified asphalt binders are obtained.

Effect of salt solutions on chain structure of partially hydrolyzed polyacrylamide

Abstract: The effect of salt solutions (NaCl, Na2SO4 and CaCl2) on the conformational properties of partially hydrolyzed polyacrylamide (HPAM) was investigated by using static laser light scattering (SLLS). The special interaction between CaCl2 solution and HPAM was also researched. Experimental results show that the chain structure of HPAM is interrelated with the charge density, the kind and the concentration of salt solutions. The mean-square radius of gyration (R z) and the second virial coefficient (A 2) of HPAM decrease with increasing concentration of salt solutions, and the salt effect tends towards the maximum when the concentration of salt solution is increased to some amount.

Passive smart self-repairing concrete beams by using shape memory alloy wires and fibers containing adhesives

Abstract: An innovative approach to increase structural survivability of concrete and maintain structural durability of concrete was developed in case of earthquakes and typhoons. This approach takes advantage of the superelastic effect of shape memory alloy(SMA) and the cohering characteristic of repairing adhesive. These SMA wires and brittle fibers containing adhesives were embedded into concrete beams during concrete casting to form smart reinforced concrete beams. The self-repairing capacity of smart concrete beams was investigated by three-point bending tests. The experimental results show that SMA wires add self-restoration capacity, the concrete beams recover almost completely after incurring an extremely large deflection and the cracks are closed almost completely by the recovery forces of SMA wires. The number or areas of SMA wires has no influence on the tendency of deformation during loading and the tendency of reversion by the superelasticity. The adhesives released from the broken-open fibers fill voids and cracks. The repaired damage enables continued function and prevents further degradation.

Experimental investigation on vibration characteristics of sandwich beams with magnetorheological elastomers cores

Abstract: A sandwich beam specimen was fabricated by treating with MR elastomers between two thin aluminum face-plates. Experiment was carried out to investigate the vibration responses of the sandwich beam with respect to the intensity of the magnetic field and excitation frequencies. The results show that the sandwich beams with MR elastomers cores have the capabilities of shifting natural frequencies and the vibration amplitudes decrease with the variation of the intensity of external magnetic field.

Dynamic damping property of magnetorheological elastomer

Abstract: Magnetorheological elastomer (MRE) is a new kind of smart materials, its dynamic mechanic performances can be controlled by an applied magnetic field. MRE is usually used as a stiffness-changeable spring in the semi-active vibration absorber. In order to get perfect vibration control effect, low dynamic damping of MRE is need. But the dynamic damping of MRE was not studied deeply in the past. The dynamic damping of MRE was studied and analyzed. The influences of different test conditions including test strain amplitude, test frequency and test magnetic field were deeply studied. MRE sample and pure silicone rubber sample were prepared and tested under different conditions. The test results show that the main source of dynamic damping is the friction between iron particles and rubber matrix. And the friction is mainly influenced by the strain amplitude and test magnetic field.

Influence of underground water seepage flow on surrounding rock deformation of multi-arch tunnel

Abstract: Based on a typical multi-arch tunnel in a freeway, the fast Lagrangian analysis of continua in 3 dimensions(FLAC3D) was used to calculate the surrounding rock deformation of the tunnel under which the effect of underground water seepage flow was taken into account or not. The distribution of displacement field around the multi-arch tunnel, which is influenced by the seepage field, was gained. The result indicates that the settlement values of the vault derived from coupling analysis are bigger when considering the seepage flow effect than that not considering. Through the contrast of arch subsidence quantities calculated by two kinds of computation situations, and the comparison between the calculated and measured value of tunnel vault settlement, it is found that the calculated value(5.7–6.0 mm) derived from considering the seepage effect is more close to the measured value(5.8–6.8 mm). Therefore, it is quite necessary to consider the seepage flow effect of the underground water in aquiferous stratum for multi-arch tunnel design.

Flame image recognition of alumina rotary kiln by artificial neural network and support vector machine methods

Abstract: Based on the Fourier transform, a new shape descriptor was proposed to represent the flame image. By employing the shape descriptor as the input, the flame image recognition was studied by the methods of the artificial neural network(ANN) and the support vector machine(SVM) respectively. And the recognition experiments were carried out by using flame image data sampled from an alumina rotary kiln to evaluate their effectiveness. The results show that the two recognition methods can achieve good results, which verify the effectiveness of the shape descriptor. The highest recognition rate is 88.83% for SVM and 87.38% for ANN, which means that the performance of the SVM is better than that of the ANN.

Numerical Simulation and Experimental Investigation of Incremental Sheet Forming Process

Abstract: In order to investigate the process of incremental sheet forming (ISF) through both experimental and numerical approaches, a three-dimensional elasto-plastic finite element model (FEM) was developed to simulate the process and the simulated results were compared with those of experiment. The results of numerical simulations, such as the strain history and distribution, the stress state and distribution, sheet thickness distribution, etc, were discussed in details, and the influences of process parameters on these results were also analyzed. The simulated results of the radial strain and the thickness distribution are in good agreement with experimental results. The simulations reveal that the deformation is localized around the tool and constantly remains close to a plane strain state. With decreasing depth step, increasing tool diameter and wall inclination angle, the axial stress reduces, leading to less thinning and more homogeneous plastic strain and thickness distribution. During ISF, the plastic strain increases stepwise under the action of the tool. Each increase in plastic strain is accompanied by hydrostatic pressure, which explains why obtainable deformation using ISF exceeds the forming limits of conventional sheet forming.

3D finite element analysis on pile-soil interaction of passive pile group

Abstract: The interaction between pile and soft soil of the passive pile group subjected to soil movement was analyzed with three-dimensional finite element model by using ANSYS software. The soil was assumed to be elastic-plastic complying with the Drucker-Prager yield criterion in the analysis. The large displacement of soil was considered and contact elements were used to evaluate the interaction between pile and soil. The influences of soil depth of layer and number of piles on the lateral pressure of the pile were investigated, and the lateral pressure distributions on the (2×1) pile group and on the (2×2) pile group were compared. The results show that the adjacent surcharge may result in significant lateral movement of the soft soil and considerable pressure on the pile. The pressure acting on the row near the surcharge is higher than that on the other row, due to the "barrier" and arching effects in pile groups. The passive load and its distribution should be taken into account in the design of the passive piles.

Relationship between diameter of split Hopkinson pressure bar and minimum loading rate under rock failure

Abstract: In order to investigate the relationship between bar diameter and loading rate of the split Hopkinson pressure bar(SHPB) setup under the failure of rock specimen and realize the medium strain rate loading of specimen, new SHPB setups with different elastic bar’s diameters of 22, 36, 50 and 75 mm were constructed. The tests were carried out on these setups at different loading rates, and the specimens had the same diameter of elastic bars and same ratio of length to diameter. The test results show that the larger the elastic bar’s diameter is, the less the loading rate is needed to cause specimen failure, they show good power relationship, and that under the same strain rate loading, specimens are broken more seriously with larger diameter SHPB setup than with smaller one.

Simulation of failure process of jointed rock

Abstract: A modified discontinuous deformation analysis (DDA) algorithm was proposed to simulate the failure behavior of jointed rock. In the proposed algorithm, by using the Monte-Carlo technique, random joint network was generated in the domain of interest. Based on the joint network, the triangular DDA block system was automatically generated by adopting the advanced front method. In the process of generating blocks, numerous artificial joints came into being, and once the stress states at some artificial joints satisfy the failure criterion given beforehand, artificial joints will turn into real joints. In this way, the whole fragmentation process of rock mass can be replicated. The algorithm logic was described in detail, and several numerical examples were carried out to obtain some insight into the failure behavior of rock mass containing random joints. From the numerical results, it can be found that the crack initiates from the crack tip, the growth direction of the crack depends upon the loading and constraint conditions, and the proposed method can reproduce some complicated phenomena in the whole process of rock failure.

Industrial experiment of copper electrolyte purification by copper arsenite

Abstract: Copper electrolyte was purified by copper arsenite that was prepared with As2O3. And electrolysis experiments of purified electrolyte were carried out at 235 and 305 A/m2, respectively. The results show that the yield of copper arsenite is up to 98.64% when the molar ratio of Cu to As is 1.5 in the preparation of copper arsenite. The removal rates of Sb and Bi reach 74.11% and 65.60% respectively after copper arsenite is added in electrolyte. The concentrations of As, Sb and Bi in electrolyte nearly remain constant during electrolysis of 13 d. The appearances of cathode copper obtained at 235 and 305 A/m2 are slippery and even, and the qualification rate is 100% according to the Chinese standard of high-pure cathode copper(GB/T467-97).

Hydraulic Calculation of Gravity Transportation Pipeline System for Backfill Slurry

Abstract: Taking cemented coal gangue pipeline transportation system in Suncun Coal Mine, Xinwen Mining Group, Shandong Province, China, as an example, the hydraulic calculation approaches and process about gravity pipeline transportation of backfill slurry were investigated. The results show that the backfill capability of the backfill system should be higher than 74.4 m3/h according to the mining production and backfill times in the mine; the minimum velocity (critical velocity) and practical working velocity of the backfill slurry are 1.44 and 3.82 m/s, respectively. Various formulae give the maximum ratio of total length to vertical height of pipeline (L/H ratio) of the backfill system of 5.4, and then the reliability and capability of the system can be evaluated.

Analysis theory of spatial vibration of high-speed train and slab track system

Abstract: The motor and trailer cars of a high-speed train were modeled as a multi-rigid body system with two suspensions. According to structural characteristic of a slab track, a new spatial vibration model of track segment element of the slab track was put forward. The spatial vibration equation set of the high-speed train and slab track system was then established on the basis of the principle of total potential energy with stationary value in elastic system dynamics and the rule of “set-in-right-position” for formulating system matrices. The equation set was solved by the Wilson-ϑ direct integration method. The contents mentioned above constitute the analysis theory of spatial vibration of high-speed train and slab track system. The theory was then verified by the high-speed running experiment carried out on the slab track in the Qinghuangdao-Shenyang passenger transport line. The results show that the calculated results agree well with the measured results, such as the calculated lateral and vertical rail displacements are 0.82 mm and 0.9 mm and the measured ones 0.75 mm and 0.93 mm, respectively; the calculated lateral and vertical wheel-rail forces are 8.9 kN and 102.3 kN and the measured ones 8.6 kN and 80.2 kN, respectively. The interpolation method, that is, the lateral finite strip and slab segment element, for slab deformation proposed is of simplification and applicability compared with the traditional plate element method. All of these demonstrate the reliability of the theory proposed.

Damping of magnetorheological elastomers

Abstract: The damping property of magnetorheological elastomers (MREs) is characterized by a modified dynamic mechanical-magnetic coupled analyzer. The influence of external magnetic flux density, damping of matrix, content of iron particles, dynamic strain and driving frequency on the MREs’ damping was investigated experimentally. The results indicate that the MREs’ damping property depends on the interfacial slip between the inner particles and the matrix. Different from the general composite materials, the interfacial slip in MRE is affected by the external applied magnetic field.

Modeling and parameter estimation for hydraulic system of excavator’s arm

Abstract: A retrofitted electro-hydraulic proportional system for hydraulic excavator was introduced firstly. According to the principle and characteristic of load independent flow distribution(LUDV) system, taking boom hydraulic system as an example and ignoring the leakage of hydraulic cylinder and the mass of oil in it, a force equilibrium equation and a continuous equation of hydraulic cylinder were set up. Based on the flow equation of electro-hydraulic proportional valve, the pressure passing through the valve and the difference of pressure were tested and analyzed. The results show that the difference of pressure does not change with load, and it approximates to 2.0 MPa. And then, assume the flow across the valve is directly proportional to spool displacement and is not influenced by load, a simplified model of electro-hydraulic system was put forward. At the same time, by analyzing the structure and load-bearing of boom instrument, and combining moment equivalent equation of manipulator with rotating law, the estimation methods and equations for such parameters as equivalent mass and bearing force of hydraulic cylinder were set up. Finally, the step response of flow of boom cylinder was tested when the electro-hydraulic proportional valve was controlled by the step current. Based on the experiment curve, the flow gain coefficient of valve is identified as 2.825 × 10−4 m3/(s·A) and the model is verified.

Mechanical mechanism analysis of tension type anchor based on shear displacement method

Abstract: Based on the fact that the shear stress along anchorage segment is neither linearly nor uniformly distributed, the load transfer mechanism of the tension type anchor was studied and the mechanical characteristic of anchorage segment was analyzed. Shear stress-strain relationship of soil surrounding anchorage body was simplified into three-folding-lines model consisting of elastic phase, elasto-plastic phase and residual phase considering its softening characteristic. Meanwhile, shear displacement method that has been extensively used in the analysis of pile foundation was introduced. Based on elasto-plastic theory, the distributions of displacement, shear stress and axial force along the anchorage segment of tension type anchor were obtained, and the formula for calculating the elastic limit load was also developed accordingly. Finally, an example was given to discuss the variation of stress and displacement in the anchorage segment with the loads exerted on the anchor, and a program was worked out to calculate the anchor maximum bearing capacity. The influence of some parameters on the anchor bearing capacity was discussed, and effective anchorage length was obtained simultaneously. The results show that the shear stress first increases and then decreases and finally trends to the residual strength with increase of distance from bottom of the anchorage body, the displacement increases all the time with the increase of distance from bottom of the anchorage body, and the increase of velocity gradually becomes greater.

Prediction of grain size for large-sized aluminium alloy 7050 forging during hot forming

Abstract: A numerical approach for process optimization and microstructure evolution of lager-sized forging of aluminium alloy 7050 was proposed, which combined a commercial FEM code Deform 3D with empirical models. To obtain the parameters of empirical constitutive equation and dynamic recrystallization models for aluminium alloy 7050, the isothermal compression tests of 7050 samples were performed on Gleeble-1500 thermo-simulation machine in the temperature range of 250–450 °C and strain rate of 0.01–10 s−1, and the metallograph analysis of the samples were carried out on a Leica DMIRM image analyzer. The simulation results show that the dynamic recrystallization in the central area of the billet occurs more easily than that on the edge. Repetitious upsetting and stretching processes make the billet deform adequately. Among several forging processes e.g. upsetting, stretching, rounding and flatting, the stretching process is the most effective way to increase the effective strain and refine the microstructure of the billet. As the forging steps increase, the effective strain rises significantly and the average grain size reduces sharply. Recrystallized volume fractions in most parts of the final forging piece reach 100% and the average grain size reduces to 10 μm from initial value of 90 μm.

Fatigue properties analysis of cracked rock based on fracture evolution process

Abstract: Fracture evolution process (initiation, propagation and coalescence) of cracked rock was observed and the force—displacement curves of cracked rock were measured under uniaxial cyclic loading. The tested specimens made of sandstone-like modeling material contained three pre-existing intermittent cracks with different geometrical distributions. The experimental results indicate that the fatigue deformation limit corresponding to the maximal cyclic load is equal to that of post-peak locus of static complete force-displacement curve; the fatigue deformation process can be divided into three stages: initial deformation, constant deformation rate and accelerative deformation; the time of fracture initiation, propagation and coalescence corresponds to the change of irreversible deformation.

New two-dimensional fuzzy C-means clustering algorithm for image segmentation

Abstract: To solve the problem of poor anti-noise performance of the traditional fuzzy C-means (FCM) algorithm in image segmentation, a novel two-dimensional FCM clustering algorithm for image segmentation was proposed. In this method, the image segmentation was converted into an optimization problem. The fitness function containing neighbor information was set up based on the gray information and the neighbor relations between the pixels described by the improved two-dimensional histogram. By making use of the global searching ability of the predator-prey particle swarm optimization, the optimal cluster center could be obtained by iterative optimization, and the image segmentation could be accomplished. The simulation results show that the segmentation accuracy ratio of the proposed method is above 99%. The proposed algorithm has strong anti-noise capability, high clustering accuracy and good segment effect, indicating that it is an effective algorithm for image segmentation.

Viscoelastic rheological property of different types of polymer solutions for enhanced oil recovery

Abstract: The capability of hydrophobic association polymer (HAPAM) to displace oil is different from that of hydrolyzed polyacrylamide (HPAM) because they have different rheological properties. The viscoelasticity of five polymers was measured using Physica MCR301 rheometer and was compared. The five polymers include three HAPAMs with relative molecular mass of 1 248×104 (Type I), 750×104 (Type II), and 571×104 (Type III) separately and two HPAMs with relative molecular mass of 1 200×104 and 3 800×104 respectively. The experiment results indicate that the viscoelasticity of HAPAM is better than that of HPAM. The storage modulus G′ and the loss modulus G″ for HAPAM solutions are also larger than those for HPAM. Comparing the rheological curves of different HAPAM types, it is found that the viscosity of type II and type III is almost same at different shear rates while the viscosity of type I is the lower than that of Types II and III. The storage modulus G′ and the loss modulus G″ for three types of HAPAM were measured in low oscillation frequency range, and the results show that G′ is greater than G″ for all three different types of HAPAM, but their loss modulus is almost same, and the G′ is in the order of type II>type III>type I. In addition, the G′ and G″ increase with aging time for all three HAPAM solutions were stayed at different days. The viscoelasticity of type I reaches the highest value when aging time is 9 d at 45 °C, but it is 7 d for type II and type III. The different viscoelasticity properties can be attributed to self-organization supermolecule networks which is formed by hydrophobic association of HAPAM molecular and molecular chain entanglement.