Showing papers by "Xi'an University of Science and Technology published in 2010"
Journal Article•
TL;DR: In this article, an improved ant colony algorithm is proposed for robot path planning under a static environment, where the grid method is used to establish workspace model of the robot, and the strategy of backspace from traps and the meeting strategy are applied to path planning of mobile robot, so it avoided path-locked situation as well as improved the efficiency of planning optimal path.
Abstract: An improved ant colony algorithm is proposed for robot path planning under a static environment.Grid method is used to establish workspace model of the robot.Furthermore,the strategy of backspace from traps and the meeting strategy were applied to path planning of mobile robot,so it avoided path-locked situation as well as improved the efficiency of planning optimal path.The simulation results show that the performance of path planning can be obviously improved by the proposed ant colony algorithm,and the algorithm is very simple and efficient.
123 citations
TL;DR: It was found that at a certain concentration, either L- or D-enantiomeric derivatives could self-assemble in absolute alcohol to form a white organogel, which was composed of ultralong nanotubes with an aspect ratio higher than 1000.
Abstract: Enantiomeric L- or D-glutamic acid based lipids were designed and their self-assembly was investigated. It was found that at a certain concentration, either L- or D-enantiomeric derivatives could self-assemble in absolute alcohol to form a white organogel, which was composed of ultralong nanotubes with an aspect ratio higher than 1000. Further investigations revealed that these nanotubes were in chiral forms. The chirality of the nanotubes was determined by that of the enantiomers employed. In addition, when D and L enantiomers were mixed in different ratios, the nanotube could be tuned consecutively from nanotubes with a helical seam to nanotwists, the chirality of which being determined by the excess enantiomer in the mixed systems. In the case of an equimolar mixture of the enantiomers, flat nanoplates instead of helical nanotubes or nanotwists were obtained. The FTIR vibrational data and XRD layer-distance values showed a consecutive change as a function of the enantiomeric excess. It was further revealed that the slightly stronger interaction between D-L enantiomeric pairs than that between D-D or L-L pairs was responsible for the formation of the diverse self-assembled nanostructures.
98 citations
TL;DR: In this paper, the thermal and dielectric properties of aluminum/epoxy composites were investigated in terms of composition, aluminum particle sizes, frequency, and temperature, and the results showed that the introduction of aluminum particles to the composites hardly influenced the thermal stability behavior, and decreased Tg of the epoxy resin; moreover, the size, concentration, and surface modification of aluminum nanoparticles had an effect on their thermal conductivity and diesels.
Abstract: Microsized aluminum/epoxy resin composites were prepared, and the thermal and dielectric properties of the composites were investigated in terms of composition, aluminum particle sizes, frequency, and temperature. The results showed that the introduction of aluminum particles to the composites hardly influenced the thermal stability behavior, and decreased Tg of the epoxy resin; moreover, the size, concentration, and surface modification of aluminum particles had an effect on their thermal conductivity and dielectric properties. The dielectric permittivity increased smoothly with a rise of aluminum particle content, as well as with a decrease in frequency at high loading with aluminum particles. While the dissipation factor value increased slightly with an increase in frequency, it still remained at a low level. The dielectric permittivity and loss increased with temperature, owing to the segmental mobility of the polymer molecules. We found that the aluminum/epoxy composite containing 48 vol % aluminum-particle content possessed a high thermal conductivity and a high dielectric permittivity, but a low loss factor, a low electric conductivity, and a higher breakdown voltage. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
78 citations
TL;DR: In this article, a saturated removal rate is incorporated into Hethcote's SIR epidemiological model, which has two endemic equilibria when R 0 < 1 and under some conditions, both the disease free equilibrium and one of the two endemic equilibrium are asymptotically stable.
Abstract: On account of the effect of limited treatment resources on the control of epidemic disease, a saturated removal rate is incorporated into Hethcote’s SIR epidemiological model (Hethcote, SIAM Rev. 42:599–653, 2000). Unlike the original model, the model has two endemic equilibria when R0<1. Furthermore, under some conditions, both the disease free equilibrium and one of the two endemic equilibria are asymptotically stable, i.e., the model has bistable equilibria. Therefore, disease eradication not only depends on R0 but also on the initial sizes of all sub-populations. By the Poincare-Bendixson theorem, Poincare index, center manifold theorem, Hopf bifurcation theorem and Lyapunov-Lasalle theorem, etc., the existence and asymptotical stability of the equilibria, the existence, stability and direction of Hopf bifurcation are discussed, respectively.
67 citations
TL;DR: In this paper, the adsorption of tramadol hydrochloride (TH) by montmorillonite (MMT) was investigated, to obtain a controlled drug release system.
52 citations
TL;DR: In this paper, the carbon nanosphere films were successfully prepared with the soot of burning rapeseed oil by means of depositing the residue of burning oil on the carbon nano-spheres.
42 citations
05 Jul 2010
TL;DR: The simulation experiments illustrate that it is workable to utilize the existing WSN to transmit the sensitive information covertly with the characteristics of lower energy costs and invisibility, and it is suitable for stream data in sensor nodes.
Abstract: Digital Image Encryption is the image processing in the field of a new branch. This paper discusses the modern cryptography, and RSA algorithms. Root According to the data features of digital image itself, designed and implemented digital image based on RSA encryption algorithm, and made further studies of the head. The wireless sensor networks, which self-organized, are data-centered. The current urgent problem with which the wireless faced is how to protect the security of the sensor data effectively. To deal with the weakness of limitation in sensor node resources and the security threats, a novel secure transmission strategy based on information hiding for sensor data security is proposed. In ordering to protect the security of the data, we obtain the sensitive information safely to make use of the advantage of information hiding technique without encryption to safeguard the data security. The simulation experiments illustrate that it is workable to utilize the existing WSN to transmit the sensitive information covertly with the characteristics of lower energy costs and invisibility, and it is suitable for stream data in sensor nodes.
38 citations
Journal Article•
TL;DR: In this paper, the damage model of freeze-thaw and loaded rock is established considering the heterogeneity of rock at mesoscopic level using damage mechanical theory and generalized principle of strain equality, and the damage evolutions of meso-structure and macro-damage behaviors of rocks are described by damage variable and constitutive equation.
Abstract: For freeze-thaw and loaded rock in engineering structures in cold regions,a damage variable is proposed with a new meaning,and three new conceptions are put forward,which are freeze-thaw damage,loaded damage and total damage. Defining the initial damage state as basic state,the damage model of freeze-thaw and loaded rock is established considering the heterogeneity of rock at mesoscopic level using damage mechanical theory and generalized principle of strain equality. The damage evolutions of meso-structure and macro-damage behaviors of rocks are described by damage variable and constitutive equation,which are in good agreement with the actual freeze-thaw breakage. It is shown that the mechanical properties of freeze-thaw and loaded rocks in engineering structures are determined by freeze-thaw,load and the coupling effects. The combined effect of freeze-thaw and load in the total damage of rock has obvious nonlinear properties,but the coupling effect will weaken the total damage. The weights of influence factors are determined by the lithology and initial damage states of the rocks,so the rock has different damage propagation characteristics. In comparison,sandstone is more sensitive to the freezethaw cycles,and load damage will lead to the destruction of shale eventually.
37 citations
Journal Article•
TL;DR: Choosing Matlab as the emulator, it is proved that the localization accuracy of the improved algorithm is better than those of the original algorithm and some existing improved algorithms.
Abstract: In the wireless sensor networks,node localization is one of the key technologiesThe authors theoretically analyzed DV-HOP algorithm and pointed out the main reason for the errorThen,an improved algorithm was brought out to use correction value as the estimated distance between anchor nodes and unknown nodesThis value was composed of the correction of the multi-hop and anchor node's average distance errorMeanwhile,Total Least Squares(TLS) was applied to node localization to enhance the localization accuracyChoosing Matlab as the emulator,it is proved that the localization accuracy of the improved algorithm is better than those of the original algorithm and some existing improved algorithms
30 citations
TL;DR: A new approach to boundary extraction by a level set model that is embedded in several scalar functions that is flexible in handling complex topological changes and concise in extracting object boundaries despite of deep depression is presented.
30 citations
TL;DR: In this paper, a broad peak of magnetic entropy change was found above the Curie temperature (T c =120 K), which can be associated with the existence of two-dimensional short range ferromagnetic order.
TL;DR: In this article, the effect of the withdrawing rate on carbide morphology was investigated in single crystal superalloy AM3 with sample growth rates from 35 μm/s to 500 μm /s.
TL;DR: In this paper, the effects of the silica content in the mixed particles on the stability and the drop size of the Pickering emulsions were investigated, and the results showed that the emulsion was of the oil-in-water type.
TL;DR: A GPGPU framework with the corresponding parallel computing solution for wavelet-based image denoising by using off-the-shelf consumer-grade programmable GPUs is presented.
TL;DR: In this article, the first-order rate constants (k1) of Cr (VI) adsorption onto WSRA, WSUA, BQRA and BQUA are 1.981, 1.497, 2.119 and 1.500 min−1, respectively.
Abstract: Coal fly ashes WSRA and BQRA were ball milled for 5 h to produce their ultrafine coal fly ashes WSUA and BQUA, respectively. Batch kinetic, isotherm and pH effect on adsorption were studied to evaluate removal of Cr (VI) from aqueous solutions by ultrafine coal fly ashes comparing with raw coal fly ashes. The kinetics of adsorption indicates the process to be intraparticle diffusion controlled and follows the Lagergren first-order kinetics for all coal fly ashes. The first-order rate constants (k1) of Cr (VI) adsorption onto WSRA, WSUA, BQRA and BQUA are 1.981, 1.497, 2.119 and 1.500 (×10−2) min−1, respectively. The adsorption capacities of WSUA and BQUA are much better than those of WSRA and BQRA. Equilibrium adsorption data of all coal fly ashes well satisfy the Langmuir isotherm. The adsorbed amounts of Cr (VI) onto WSUA and BQUA decrease from pH 2 to pH 6 and then increase up to pH 12.
TL;DR: In this article, an iron-based composite coating, reinforced by tungsten carbide (WC) particles, with a thickness of 3.0mm, was fabricated on the surface of a gray cast iron substrate by centrifugal casting plus in-situ synthesis techniques.
Abstract: Using tungsten wires as a reactive source, an iron-based composite coating, reinforced by tungsten carbide (WC) particles, with a thickness of 3.0 mm, was fabricated on the surface of a gray cast iron substrate by centrifugal casting plus in-situ synthesis techniques. With the help of differential thermal analysis (DTA), an appropriate pouring temperature of the gray cast iron molten was determined to be 1300 °C. The experimental results show that the composite coating is dense and consists mainly of primary WC carbides, fine secondly WC carbides as the reinforcing phases and pearlite accompanied by negligible graphite flakes as the matrix. Wear resistance of the composite coating was determined with a pin-on-disc wear test technique, indicating that the composite coating, containing high volume fraction of hard WC carbides, present good wear resistance property compared with the un-reinforced gray cast iron, regardless of load level. Additionally, according to the Fe–W–C ternary phase, reaction paths between tungsten wires and molten, and in-situ synthesis of WC particles, were investigated.
09 Apr 2010
TL;DR: The experimental results show that the algorithm can reduce time complexity and maintain robust quality at the same time and the Chamfer distance is used in this article; it decreases computation time and improves the accuracy of image matching.
Abstract: Due to good invariance of scale, rotation, illumination, SIFT (Scale Invariant Feature Transform) descriptor is commonly used in image matching. The steps of extracting SIFT feature are analyzed in detail, and SIFT Key-point location is optimized. The Chamfer distance is used in this article; it decreases computation time and improves the accuracy of image matching. The experimental results show that the algorithm can reduce time complexity and maintain robust quality at the same time.
TL;DR: In this article, the agglomeration mechanism of micro-and nanosize aluminum particles with a primary mean particle diameter of 4.5 µm and 75 nm, respectively, was comparatively investigated under an incident shock wave.
TL;DR: The effect of inert gases on the explosive limits of mixed gases, given the property of explosive gas, is obvious: the inert gases (N2, CO2) possess some inhibitory effects on the explosion of the multi-component explosive gas mixtures.
Abstract: The explosive gases CO and C2H4, released mainly flammable gases during the process of coal self-ignition, are of the most important ingredients of the multi-component gases in goaf areas, along with CH4. We have determined some of the parameters of explosive properties of the one-component gases CH4, CO and C2H4 using an explosive trial device of polybasic explosive gas mixtures and emphasized particularly the effect on the limits of explosive concentration of the binary explosive mixed gases CH4+CO, CH4+C2H4, as a function of the amount of CO, C2H4 and inert flame resisting gases (N2, CO2). The experimental results show that the effect of inert gases on the explosive limits of mixed gases, given the property of explosive gas, is obvious: the inert gases (N2, CO2) possess some inhibitory effects on the explosion of the multi-component explosive gas mixtures. The results will provide some experimental support to suppress the occurrence of the gas explosions in goaf areas and provide some directions for designing explosion-proof electric equipment and fire arresters.
TL;DR: In this paper, the authors investigated the effect of CO 2 on the explosion limits of polybasic explosive gas mixtures and showed that CO 2 has a better suppression effect than N 2.
Abstract: In order to reduce the number of accidents due to explosions of flammable gases in the goaf of coalmines, the conditions for explosion of flammable gases and their explosion limits, affected to a considerable extent by CO 2 , are explored. With the use of our experimental equipment suitable for the study of explosion of polybasic explosive gas mixtures, we investigated the effect of CH 4 /H 2 =10/1 and CH 4 /C 2 H 4 =10/1 gases mixed with CO 2 on their explosion limits. The results indicate that after adding CO 2 , the explosion limit of the CH 4 /H 2 (or C 2 H 4 ) =10/1 gas mixtures decreased markedly with increasing amounts of CO 2 . When the amount of CO 2 exceeded 25%, the CH 4 /C 2 H 4 =10/1 flammable gas mixture did not lead to explosions. Similar results were obtained when the amount of CO 2 exceeded 23% in the CH 4 /H 2 =10/1 flammable gas mixture. We also compared the explosion limits and the explosion suppression effect of N 2 or CO 2 on the explosion limits of the CH 4 +CO and CH 4 +C 2 H 4 dual explosive gas mixtures. Along with the increases in the amounts of CO 2 or N 2 , the area of the explosion limits of gas mixtures decreased. Under the same conditions, the explosion suppression effect of CO 2 was greater than that of N 2 . CO 2 has clearly the better suppression effect on the explosion of flammable gases in goafs.
TL;DR: Based on the coal gangue in Weibei Coalfield, such as petrologic characteristics, chemical composition, nutrient elements, deleterious elements, and transformation, and compared with the soil element content background values of Loess Plateau and national harmful materials controlling standards, Wang et al. as discussed by the authors concluded that coal gangues in the Wei coalfield has huge potential to be used as clay fertilizer.
Abstract: Based on the systematic analysis of the coal gangue in Weibei Coalfield, such as petrologic characteristics, chemical composition, nutrient elements, deleterious elements, and the transformation, and compared with the soil element content background values of Loess Plateau and national harmful materials controlling standards, we conclude that the coal gangue in the Weibei Coalfield has huge potential to be used as clay fertilizer.
TL;DR: In this paper, the attenuation coefficients of electric field in horizontal and vertical polarization were deduced through the traveling wave condition of confined space in coal mine tunnels, and the authors showed that the electric field intensity increases quickly in 50m.
Abstract: The radio waves are more complex in confined environments such as coal mine tunnels, in order to obtain the propagation character of radio wave in the confined environments of mine tunnel, the electric-field intensity and magnetic-field intensity of horizontal polarization wave are obtained according to Maxwell equation and boundary condition of tunnel. The attenuation coefficients of electric field in horizontal and vertical polarization are deduced through the traveling wave condition of confined space. The attenuation characters of different position transmitter in rectangular mine tunnels are simulated in an experiment tunnel. The results shows the attenuation of electric-field intensity is increase quickly in 50m.When the transmitter is more close to the wall of the mine tunnel, the mode of propagation is more complex and the attenuation is more serious, whereas in the middle of the mine tunnel, the attenuation rate of radio is the least. Factors that influence the attenuation character of radio waves in mine tunnel are analysed and simulated too, it is benefit to evaluate the wireless channel quality in mine tunnel.
Journal Article•
TL;DR: Based on the roof structure around the coal face in steeply dipping seam, the theoretical analysis, physical simulation experiments and numerical simulation were used to analyze the stress distribution and movement of the roof.
Abstract: Based on the roof structure around the coal face in steeply dipping seam,the theoretical analysis,physical simulation experiments and numerical simulation were used to analyze the stress distribution and movement of the roofAccording to the conclusion,the incline masonry structure was formed after the roof failure,of which the dip direction pile and anti-dip direction types were made,and different distribution of the structure was concluded around the coal face,the nondirective movement was found when the coal face is moving forward,which is also the main reason of the instability of"R-S-F"systemAt the same time,the behavior of incline masonry structure is affected by the upper strata structure which can be defined as the key load-bearing structure,therefore,the incline masonry structure is not only loader of the support,but also load medium between the support and the key load-bearing structureAt last,the study of the incline masonry structure is the key point to discuss mechanism of the key load-bearing structure failure and catastrophe
Journal Article•
TL;DR: Wang et al. as discussed by the authors investigated the influence of confining pressure and freezing temperature on the triaxial strength properties of frozen rock and found that the water-rich sandstone is more sensitive to temperature than that of coal.
Abstract: With the demands of fundamental construction in cold regions or special construction environment,it is more necessary to research the problems occurring in frozen rock mechanics. Taking the frozen shaft project of Hujia River coal mine in Shaanxi Bingchang coal mine area as the project background,sandstone and coal samples collected from the field,respectively,are tested under the triaxial compression at different confining pressures at the room temperature 20 ℃ and different freezing temperatures of-5 ℃,-10 ℃ and-20 ℃ . Based on the experimental results,the influential law of confining pressure and freezing temperature on the triaxial strength properties of frozen rock is explored;and the strength properties of sandstone and coal samples under the same confining pressure at different temperatures and different confining pressures at different freezing temperatures are analyzed;and the identity and discrepancy of two rock samples on freezing temperature are comparatively studied. Due to the internal structural difference,the frozen effects of sandstone and coal exist obvious difference. Frozen water-rich sandstone is more sensitive to temperature than that of coal. Strength of the water-rich rocks increases with the decrease of temperature which is mainly due to the peak intensity of rocks greatly improved by mineral contraction and ice strength and frost heave force with temperature decreasing. The result provides some references for studying rock mechanics under cold environment and the construction and design for freezing shafts of coal mines.
TL;DR: In this article, the authors studied the mechanism of coal and gas outbursts due to instability, under the action of in-plane load and normal load, by using the catastrophe theory.
Abstract: Based on the engineering observations of coal and gas outbursts during mining processes and the experimental results, we built a thin plate mechanical model for layered and spalled coal bodies. We studied the mechanical mechanism of outbursts, due to instability, of thin plates of coal rocks under the action of in-plane load and normal load, by using the catastrophe theory. The total potential function is derived for the layered rock system, the cusp catastrophe model for the system is established, the bifurcation set that makes the system unstable is given, the process in which gradual change of action forces leads to catastrophic change of state is analyzed, and the effect of movement path of point (P, q) in the control space on the stability of rock plate is analyzed. The study results show that during the process of coal mining, the stability of the layered coal bodies depends not only on its physical properties and dimensions but also on the magnitudes and changing paths of the in-plane load and the normal load. When the gas in the coal bodies ahead of the mining face is pre-drained, the gas pressure can be reduced and the normal load q can be lowered. Consequently, disasters such as coal and gas outbursts can be effectively prevented.
TL;DR: Achiral diacetylene 10,12-pentacosadinoic acid (PCDA) and a chiral low-molecular-weight organogelator could form co-gel in organic solvent and it could be polymerized in the presence of Zn(II) ion or in the corresponding xerogel under UV-irradiation.
Abstract: Achiral diacetylene 10,12-pentacosadinoic acid (PCDA) and a chiral low-molecular-weight organogelator could form co-gel in organic solvent and it could be polymerized in the presence of Zn(II) ion or in the corresponding xerogel under UV-irradiation. Optically active polydiacetylene (PDA) were subsequently obtained. Supramolecular chirality of PDA could be controlled by the chirality of gelators. Left-handed and right-handed helical fibers were obtained by using L- and D-gelators in xerogels respectively, and CD spectra exhibited mirror-image circular dichroism. The PDA in xerogel exhibited typical blue-to-red transition responsive to the temperature and pH, while the supramolecular chirality of PDA showed a corresponding change.
TL;DR: In this paper, the authors summarized and concluded the basic contents and evaluation methods of ecological carrying capacity with regard to the related studies of the domestic and foreign scholars, and provided a more comprehensively summarized and concludes evaluation method.
Abstract: The ecological carrying capacity is of vital importance for the economic development and the scale of resource exploitation in one country or region. This paper more comprehensively summarizes and concludes the basic contents and evaluation methods of ecological carrying capacity with regard to the related studies of the domestic and foreign scholars.
Journal Article•
TL;DR: Based on analyzing the thermal effects of pile construction on pile foundation in permafrost regions, the variation laws of radial temperature field and the thermal perturbation radius of pile foundation caused by cement hydration heat are studeied.
Abstract: Based on analyzing the thermal effects of pile construction on pile foundation in permafrost regions,the variation laws of radial temperature field and the thermal perturbation radius of pile foundation caused by cement hydration heat are studeied.In view of the transient temperature field equations,nonlinear transient temperature field equations for piles and forzen soil are respectively fomulated.Considering the boundary conditions and freeze-thaw process of transformation,a finite element model of transient temperature field for pile foundation in cold regions is established.The model is employed to simulate the thermal perturbation of pile foundation caused by cement hydration heat.The variation laws of radial temperature field with time at different depths and thermal perturbation regions about 6 times the radius of pile diameter are acquired.The results show that the hydration heat has significant thermal perturbation and long-term effects on the thermal stability of pile foundation.In order to reduce the perturbation,it is essensial to reduce the hydration heat of concrete in permafrost regions.
TL;DR: In this paper, the authors used positron annihilation lifetime spectra to provide direct evidence for defect characterization for BZNM ceramics with different tetravalent elements, and described the defect structure by means of the complex defect model.