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15 July 2005, Volume 26 Issue 7 Previous Issue    Next Issue
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Robust fault-tolerant guaranteed cost control for fuzzy descriptor system with uncertain parameters Zhu, Bao-Yan (1); Zhang, Qing-Ling (1); Da, Ke-Ning (2); Li, Hai-Yan (2) 2005, 26 (7):  613-616.  DOI: - Abstract ( 240 )   HTML   PDF (283KB) ( 560 )   The problems of robust fault-tolerant guaranteed cost control for T-S fuzzy descriptor system with uncertain parameters and actuator failure are studied. A sufficient condition for the existence of robust fault-tolerant guaranteed cost controller is given for all admissible uncertainties. Under the condition, the designed controller not only provides the asymptotical stability of the closed-loop system but also guarantees the performance at an adequate level. The nonstrict LMIs for the descriptor system are transformed into strict ones by means of the matrix decomposition. The drawback that the LMI toolbox can't be used directly is thus overcome for descriptor system. In this way the solutions to the controller can be given via the LMI toolbox like the normal system. An illustrative example is given to show the feasibility and validity of the proposed approach. References | Related Articles | Metrics

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Dynamic model and simulation of biped robot with heterogeneous legs Fu, Li (1); Wang, Bin-Rui (1); Xu, Xin-He (1) 2005, 26 (7):  617-620.  DOI: - Abstract ( 288 )   HTML   PDF (1487KB) ( 586 )   A special research was done on the dynamic modeling of a biped robot with heterogeneous legs of which one is a bionic leg and the other is an intelligent prosthesis. To make the robot walk with an expected gait, a special multi-pivot mechanism with closed chain was designed and used at the knee joint of the intelligent prosthesis, but it brought a difficulty to the dynamic modeling if comparing it with the single-pivot mechanism. For the characteristics of closed chain with redundant coordinates, the Routh equation was applied to developing a dynamic model of the biped robot with heterogeneous legs to which the relationship between force and moment of the two legs are evaluated, thus giving dynamically the direct and inverse solutions to the Routh equation. A simulation was also carried out to calculate the equation of dynamic model with typical gait data. The result showed that the reluctant constraint equation can therefore be avoided. What the research concluded provides a foundation to investigate further the locomotion, control and perception of the robot. References | Related Articles | Metrics

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CIMS-based R&D of supply system for iron and steel industry Gao, Xian-Wen (1); Liu, Wen-Hui (1); Wang, Tao (1) 2005, 26 (7):  621-624.  DOI: - Abstract ( 209 )   HTML   PDF (165KB) ( 558 )   An overall design of CIMS was carried out for Handan Iron and Steel Co. by way of a three-level architecture available to flow-process industries, i.e., ERP (enterprise resource planning)/MES (manufacturing execution system)/PCS (process control system). Then, the design objectives and main tasks of the supply system and the technological way adoptive to it were determined in combination with the ready experience in management of the company. Introduces the design of systematic function module, integrating of relevant system, database and network architecture. Based on the overall design, the subsystems of supply, as the integral part of CIMS, were developed and proved successful by debugging in situ. Complete information and functions, easy to operate, high maneuverability and friendly man-machine interface feature the system with user's satisfaction. References | Related Articles | Metrics

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Novel multiresolution DOA estimation method with wavelet packets Xue, Yan-Bo (1); Wang, Jin-Kuan (1); Liu, Zhi-Gang (1); Li, Hong-Jie (1) 2005, 26 (7):  625-628.  DOI: - Abstract ( 225 )   HTML   PDF (186KB) ( 691 )   A novel wavelet packets-based DOA (direction of arrival) estimation method is proposed for the rapid performance degradation of typical multiple signal classification (MUSIC) algorithm in the scenario where different signals' DOA are close together even coherent, i.e., the subband-based MUSIC algorithm (SB-MUSIC). The SB-MUSIC decomposes the fullband signal into subbands and chooses the optimal leaf nodes in accordance to the best basis criterion. Then, the MUSIC method is applied to every leaf node chosen so as to estimate individually the subband spectrum. The advantages of subband spectra, such as improving SNR and amplifying frequency spacing, are analyzed taking account of that when using SB-MUSIC only the fullband makes sense, thus giving a way for frequency mapping from subband back to fullband. Simulation results showed that SB-MUSIC will not only improve the resolution of classical eigenstructure-based methods but also decouple the coherent signals if the fullband is properly decomposed into subbands. In particular, the rate of success of estimation and spectral flatness measure (SFM) of subband are obviously higher than that of fullband. References | Related Articles | Metrics

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Unitary cyclic MUSIC algorithm based on real-valued decomposition technique Liu, Zhi-Gang (1); Wang, Jin-Kuan (1); Xue, Yan-Bo (1); Wang, Tao (1) 2005, 26 (7):  629-632.  DOI: - Abstract ( 213 )   HTML   PDF (167KB) ( 486 )   Based on real-valued decomposition technique, the unitary cyclic MUSIC algorithm is proposed for multipath environment of mobile communication by reconstructing a data model of the cyclic convariance matrix with Hermitian property. Then, a novel cyclic convariance matrix with centro-Hermitian property is designed via spatial smoothing. Thus, a favorable performance is obtained in the presence of multipath propagation. In addition, this approach is available to reduce the computational complexity by real-valued eigendecomposition and be allowed to select desired signals. The simulation results showed that this algorithm performs better not only for independent signals but also for the multipath environment covering coherent signals with lower computational complexity in-comparison with cyclic MUSIC algorithm. References | Related Articles | Metrics

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OTST-ESPRIT algorithm and it's performance Liu, Fu-Lai (1); Wang, Jin-Kuan (1); Yu, Ge (1) 2005, 26 (7):  633-636.  DOI: - Abstract ( 266 )   HTML   PDF (304KB) ( 527 )   An OTST-ESPRIT algorithm is proposed after discussing the joint estimation algorithm of direction of arrival (DOA) and delay for multipath signals in wireless network communication environment, delay and DOA are estimated by the OT-ESPRIT algorithm and OS-ESPRIT algorithm in the proposed algorithm, respectively. Only the one-step eigenvalue decomposition (EVD) is needed to estimate delay or DOA, making use of the OT-ESPRIT or OS-ESPRIT algorithm. Multiple EVDs are thus avoided efficiently to lower the complexity of TST-ESPRIT algorithm. Gramer-rao bound of the joint estimation of DOA and delay is then given for the multipath signal model. Computational complexity of the proposed algorithm is analyzed. Some simulations are provided to justify the proposed algorithm. References | Related Articles | Metrics

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Microstructure of semi-solid ZL201 alloy in electromagnetic field Wang, Ping (1); Kang, Hao (1); Lu, Gui-Min (1); Cui, Jian-Zhong (1) 2005, 26 (7):  637-639.  DOI: - Abstract ( 225 )   HTML   PDF (175KB) ( 499 )   Studies the microstructure of the semi-solid slurry of ZL201 alloy in AC electromagnetic field where a stirring or oscillating action is exerting on the alloy melt. The results show that the AC electromagnetic field has an obvious refining effect on the microstructure of the alloy slurry, i.e. the fine near-spherical crystal grains take place in the vicinity of liquidus temperature or 650°C. Such a microstructure is superior to that not put in electromagnetic field and suitable for semi-solid forming. The convection in metal as forced by the electromagnetic field will cause the secondary branches of the primary dendrites to break off or burn out at root when the temperature is fluctuating violently, which is just the key reason why the number of crystal nuclei increases in the slurry and the microstructure becomes finer and more uniform. References | Related Articles | Metrics

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DIFT grain growth in low carbon steel during cooling Wang, Kai (1); Wang, Li-Jun (1); Ren, Hai-Peng (1); Liu, Chun-Ming (1) 2005, 26 (7):  640-643.  DOI: - Abstract ( 227 )   HTML   PDF (275KB) ( 656 )   The evolution process of DIFT (deformation induced ferrite transformation) microstructure in low carbon steel at the temperature slightly higher than Ar3 as well as the effect of subsequent continuous cooling/holding process at different temperatures on DIFT microstructure was investigated using thermo-simulator. The experimental results showed that although the volume fraction of DIFT microstructure increases with increasing true strain, such an increase hasn't found in a part of austenite even after a heavy deformation. The deformed austenite is transformed into coarse ferrite in a static transformation mode during the subsequent cooling, thus forming a mixed crystal microstructure. Both the experimental and theoretical calculation results confirm that, during the continuous cooling after deformation, there is a critical temperature below which the grain growth in DIPT microstructure will stop. During the holding at different temperatures after deformation, the grain growth will become very slow when the holding temperature is lower than a certain temperature. References | Related Articles | Metrics

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On-line functioning of setup calculation module in plate rolling Jiao, Zhi-Jie (1); Hu, Xian-Lei (1); Zhao, Zhong (1); Liu, Xiang-Hua (1) 2005, 26 (7):  644-647.  DOI: - Abstract ( 311 )   HTML   PDF (222KB) ( 617 )   How to function the parameter setup calculation in the process control system for plate rolling was studied. The parameter setup calculation was divided into three parts, i.e., rolling scheduling relevant mill setup and control parameters and model learning control, of which the main functions and relations among them were analyzed. The on-line data flow and calling logic of the setup calculation were designed. According to the arrangement of monitors/probes and scheduled rolling technological process, the setup calculation can be called time and again. By means of the presetting and resetting calculations including the modifications of different rolling phases and passes, learning control and holding time, the parameter setup calculation embedded in the process control system of plate mill has functioned as the on-line actual data during rolling. References | Related Articles | Metrics

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Analysis of influence of work roll profile on side camber of plate Hu, Xian-Lei (1); Tian, Yong (1); Zhao, Zhong (1); Liu, Xiang-Hua (1) 2005, 26 (7):  648-651.  DOI: - Abstract ( 189 )   HTML   PDF (318KB) ( 625 )   Analyzing the relation between the work roll profile and side camber of plate indicates that the side camber is liable to occur on workpiece with low stability during rolling if the work roll profile is convex. The off-line simulation results revealed that (1) if the backup roll crown and workpiece width remain unchanged, when the no-load work roll profile changes from convex to concave the loaded work roll crown lowers gradually; (2) if the backup roll crown remains unchanged, the wider the workpiece, the bigger the variation range of the loaded work roll crown; (3) when the backup roll profile changes from convex to concave, the loaded work roll profile or curved surface will translate upwards as a whole. The following measures are thus recommended to take to control the side camber of plate: (1) the top work roll profile should be ground into concave to a certain range before rolling; (2) the backup roll profile should be ground into convex to a certain range; (3) at the early stage of rolling process a considerable number of the workpieces to be processed into narrow plates should be scheduled. References | Related Articles | Metrics

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Dust and particles in pelletizing shaft furnace Dong, Hui (1); Cai, Jiu-Ju (1); Wang, Guo-Sheng (1) 2005, 26 (7):  652-655.  DOI: - Abstract ( 251 )   HTML   PDF (190KB) ( 902 )   Based on the theory of gas/solid packed beds, the pelletizing shaft furnace (PSF) of Jinan Iron and Steel Co. Ltd was investigated for the formation, harm and control of the dust and particles (DP) in PSF. Some conclusions are therefore drawn as follows. The quantity of DP in PSF is equal to the difference of mass flux between dry pellets and finished pellets, and DP are formed mainly in three ways, i.e., cracking, free falling and collision. The deposits of cycling DP are difficult to remove out. From the drying zone to the soaking zone the formation rate of DP decreases gradually with the increasing DP accumulation, while the DP accumulation amount decreases abruptly at the bottom of internal vertical air channels (IVAC) because of the cycling of deposited DP. The increasing DP in PSF will result in reducing capacity utilization of PSF and increasing energy consumption for pelletizing process. The efficient way to control DP in PSF is collecting and sucking them out of PSF with gas flow through IVAC bottom by gravitational precipitation. Then, the clean gas flow returns PSF to intensify the drying of green pellets. References | Related Articles | Metrics

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Electrochemistry properties of spinel LiMn2O4 prepared by solid reaction Xu, Cha-Qing (1); Tian, Yan-Wen (1); Wu, Ji-Jun (1); Zhai, Yu-Chun (1) 2005, 26 (7):  656-659.  DOI: - Abstract ( 215 )   HTML   PDF (206KB) ( 705 )   The spinel LiMn2O4 was synthesized at 700, 750, 800 and 850°C separately by solid reaction, of which different samples were investigated via X-ray diffraction, scanning electron microscopy, cyclic voltammetry and AC impedance testing. The results showed that the lattice constants of all samples are greater than that of the standard spinel LiMn2O4, with finer grain size distributed in the range 0.2-0.4 μm. The cyclic voltammetric testing result indicated that the Li+ deinsertioninsertion process is performed in two steps and the electrode surface is passivated, then gradually stabilized in the cyclic process, especially the cyclic voltammetric curve of the sample synthesized at 750°C shows good symmetry. The AC impedance testing showed that the electrode process is controlled by two state parameters instead of one. References | Related Articles | Metrics

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Performance of Ni/MH batteries with NiOOH-Doped nickel positive electrode Yu, Tao (1); Liu, Yan (1); Zhai, Yu-Chun (1); Yan, Yong-Heng (2) 2005, 26 (7):  660-662.  DOI: - Abstract ( 210 )   HTML   PDF (155KB) ( 965 )   The secondary nickel-metal hydride (Ni/MH) batteries were developed and their performance was investigated, of which the active material of positive electrodes were made from commercial Ni(OH)2 spherical powder doped with NiOOH that was proportionately synthesized via oxidation. Constant current charge/discharge and AC internal impedance were tested to characterize the electrochemical performance of AA-type cylindrical alkaline Ni/MH batteries with rated capacity 1.5 Ah. The experimental results showed that the Ni/MH batteries developed exhibit better performances in activation efficiency and cycle life than the conventional ones because of their higher reaction activity and lower electrochemical impedance to NiOOH. It was proved that when the content of the dopant NiOOH was 1%-3% in the active material for nickel positive electrode, the electrochemical performance of the batteries can further be improved. Otherwise, overdoping of NiOOH will decrease the discharge capacity of the batteries. References | Related Articles | Metrics

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Numerical simulation of reversible chemical reaction and mass transfer process in porous media Li, Ming-Chun (1); Xu, Zeng-He (1); Tian, Yan-Wen (1); Zhai, Yu-Chun (1) 2005, 26 (7):  663-666.  DOI: - Abstract ( 314 )   HTML   PDF (309KB) ( 1176 )   The chemical reactions between fluid and porous matrix affect greatly the mass transfer process in porous media. A convection-reaction-diffusion mathematical model is thus developed by deriving a comprehensive formula of the representative elementary volume (REV), to describe the mass transfer process in porous media when the fluid and porous matrix take reversible chemical reaction. A numerical solution to the model is available by way of the finite volume implicit method. Taking the indirect reduction of iron ore in static bed into account, the influences of such main parameters as flow rate, particle size, equilibrium constant in chemical reaction and reaction rate and the ratio of the Peclet number to the Thiele number on the distribution of gas concentration and of fractional solid conversion are all analyzed. The results are useful for the conceptual design and operation of reactor. References | Related Articles | Metrics

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Enhancing the digestion efficiency of diaspore ore pulp by sweetening technique Zhang, Ting-An (1); Wang, Yan-Li (1); Wang, Yi-Yong (1); Dou, Zhi-He (1) 2005, 26 (7):  667-669.  DOI: - Abstract ( 248 )   HTML   PDF (205KB) ( 728 )   Al(OH)3 was introduced as additive to enhance the digestion efficiency of the diaspore ore pulp by sweetening technique and the digestion processs was investigated experimentally, especially effects of the mole fraction of the diaspore pulp before adding the Al(OH)3 in it, digesting temperature, dosage of Al(OH)3 and time for sweetening on the alumina thus produced. The results revealed that the appropriate conditions for digestion process are as follows: the mole fraction of the pulp should be controlled in the range from 1.55 to 1.60; sweetening temperature 210-220°C and time 15-20 min; Al(OH)3 dosage 10%-15% of the pulp. Under such conditions, the digestion efficiency of alumina can be increased to over 88.8% with the mole fraction of the solution less than 1.4 after sweetening process. References | Related Articles | Metrics

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Trajectory planning and simulating of 3-TPT parallel machine tool Yang, Bin-Jiu (1); Cai, Guang-Qi (1); Luo, Ji-Man (1); Shi, Hong (1) 2005, 26 (7):  670-672.  DOI: - Abstract ( 262 )   HTML   PDF (482KB) ( 608 )   The 3-TPT parallel machine tool developed by Northeastern University was investigated. Based on a structure analysis, the 3-TPT parallel mechanism shows the translation as its kinematic feature. The position equation is given as well as both the direct and inverse kinematic solutions to it. How the telescopic rod of driving link moves due to the movable platform which is moving in accordance to a planned movement was discussed and proposed. The planned trajectory was verified via a kinematic simulation done for the virtual prototype. The results showed that the way proposed to plan the trajectory is simple to implement with favorable applicability. References | Related Articles | Metrics

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Prediction of high-temperature low-cycle fatigue life of aeroengine's turbine blades at low-pressure stage Chen, Li-Jie (1); Xie, Li-Yang (1) 2005, 26 (7):  673-676.  DOI: - Abstract ( 216 )   HTML   PDF (325KB) ( 1005 )   Develops a full-size finite element model of turbine blades at low-pressure stage. According to the test-rig used and actual working load, an elasto-plastic finite element analysis was made using the software ANSYS with the loads due to centrifugal force and airflow pressure to operating blades taken into account. The effect of fit clearance between hoping strips and blades orifices on the stress distribution on blade was explored. It was found that the weak points of the static blade strength are the first throat section of blade tenon, the blade orifices and the side round root of blade back. Then, a high-temperature low-cycle fatigue life was predicted for the turbine blades. The results showed that the maximum fit clearance between hoping strips and blade orifices affects greatly the static strength and fatigue life of blades, and the mean fit clearance should be taken into consideration when calculating fatigue life. In addition, the calculated fatigue life of blades lowers greatly with the increasing temperature. References | Related Articles | Metrics

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Mathematical models of cylindricality error with sampling points in rectangular spatial coordinates Chen, Li-Jie (1); Zhang, Lei (1); Zhang, Yu (1) 2005, 26 (7):  677-679.  DOI: - Abstract ( 242 )   HTML   PDF (267KB) ( 974 )   An attempt is made to solve radically the key problem on evaluating the cylindricality error with sampling points in rectangular spatial coordinates. According to the definition of cylindricality error as specified in the national standards, a mathematical model was developed to evaluate the cylindricality error by least square method, to which the origin of coordinates can be randomly selected and no isogonal requirements for sampling points. The simulated results are found highly coincident with the calculated results by the model, and the error arising from the model is negligible. Based on the model, the cylindricality in conformity with minimum conditions can be calculated by way of four-dimensional non-restraint optimization algorithms. The model can be used on either measuring machines with rectangular spatial coordinates or other intelligent measuring instruments. References | Related Articles | Metrics

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Point cloud fitting of NURBS curved surface in reverse design of automobiles Zhao, Yu-Ming (1); Zhang, Guo-Zhong (1); Yu, Zhe-Feng (1) 2005, 26 (7):  680-682.  DOI: - Abstract ( 445 )   HTML   PDF (113KB) ( 1881 )   A group of point cloud data is obtained by way of no contact CDD photogrammetry for reverse design of automobiles. The point cloud data are screened and classified with combining the three softwares together, i.e., Tritop, Atos and CATIA, thus making a characteristic curve net for the point cloud data by curve fitting technique. Then, a relevant curved surface is shaped using the fitting technique of NURBS curved surface. Comparing the curved surface thus shaped with the original point cloud data, the errors of the curved surface are analyzed and the result shows that only the error at recess edge increases a bit in a very small range. It conforms with the actual requirement for design. The way applying several softwares in combination to curved surface shaping is therefore proved available to reverse design of automobiles. References | Related Articles | Metrics

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Parametric correlation between expansion deformation of coal mass and adsorption thermodynamics Wu, Shi-Yue (1); Zhao, Wen (1); Guo, Yong-Yi (2) 2005, 26 (7):  683-686.  DOI: - Abstract ( 260 )   HTML   PDF (286KB) ( 1081 )   Different coal samples were tested for their adsorptive capacities so as to determine their adsorbability parameters with CO2, CH4 and N2 as adsorbates. According to moistened length as adsorbed by porous media, model of pore structure, surface physico-chemistry and elasticity, the formulas of adsorptive expansion stress and strain of coal mass are derived. In addition, the influence of such parameters as adsorption constants, temperature, gas pressure, specific surface area of coal mass and the cross section area adsorbing gas molecules on the stress and strain are discussed. The formulas can be used more widely than existing ones and easy to calculate the strain and stress under different restrictive conditions. The bigger the specific surface area of coal mass and the cross-section area adsorbing gas molecules, the higher the gas adsorbability and the adsorptive expansion stress and strain of coal mass. References | Related Articles | Metrics

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Isolation of Sphaerotilus natans and its biosorption of Pb2+ Qin, Yu-Chun (1); Guan, Xiao-Hui (2); Wei, De-Zhou (1); Shen, Yan-Bai (1) 2005, 26 (7):  687-690.  DOI: - Abstract ( 245 )   HTML   PDF (160KB) ( 698 )   Improving the technique of culture separation, the strain Sphaerotilus natans was isolated from a kind of wastewater. A test was done for its colonial morphology, biochemical and physiological features, growth curve, culture preservation and biosorption of heavy metals. The strain was identified to be of Sphaerotilus as the 14th group of sheathed bacteria. Testing results showed that Sphaerotilus natans has excellent effect on adsorption of Pb2+. The biosorption can reach equilibrium within 10 minutes. The removal rate of Pb2+ approaches to 100% under conditions that pH=5.5, drying biomass =0.6 g/L and initial Pb mass concentration ρ0&le20 mg/L. References | Related Articles | Metrics

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Study on screening for flocculant-producing strain BS-5 and its features Hu, Xiao-Min (1); Dong, Yi-Hua (1); Li, Liang (1) 2005, 26 (7):  691-694.  DOI: - Abstract ( 225 )   HTML   PDF (192KB) ( 479 )   A strain named BS-5 was screened from river bed sludge. Its metabolin has a high and stable flocculability and can be used as a microbial flocculant through proper culture. After optimizing the cultural conditions, the strain produced a highly activated flocculant MBFBS-5 with a flocculating rate up to 97.5% in Kaolin suspension. Then, the relationship of the time for culture to its flocculability and the distribution of the flocculating activity in culture medium was studied. The thermal stability and the effect of MBFBS-5 dosage and pH value on flocculability were also researched in Kaolin suspension. The results showed that it has such advantages as short culturing time, low dosage, wide pH range and high thermal stability. The results of applying it to the wastewater treatment in beer industry indicated that MBFBS-5 has a high flocculability by which the removal rate of COD is up to 79.2%. References | Related Articles | Metrics

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Analysis of creep effect on prestressed steel composite beams with high-strength concrete Wang, Lian-Guang (1); Liu, Li (1); Cui, Jing-Qi (2) 2005, 26 (7):  695-698.  DOI: - Abstract ( 194 )   HTML   PDF (236KB) ( 797 )   Under the action of long-time loading, creep and shrinkage deformation will come to being in the high-strength concrete of a prestressed steel composite beam with flexible shear connectors, thus causing the stress to redistribute in concrete slab and steel beam. Introducing a comprehensive method combining the age-adjusted effective modulus with mean stress and considering the deformation relationships among the concrete slab, steel beam and prestressed cable, two mathematic models are developed separately for the elastic analysis of the simply supported composite beam and the viscoelastic analysis of the same beam with the creep effect on the concrete taken into account. With the numerical computation/analysis program discussed through an example, the moment, strain variation, deformation properties and the interface slip of the simply supported composite beam are analyzed. References | Related Articles | Metrics

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Deformation calculation of prestressed steel composite beams with high-strength concrete Liu, Li (1); Wang, Lian-Guang (1); Hou, Xian-Yu (2) 2005, 26 (7):  699-702.  DOI: - Abstract ( 199 )   HTML   PDF (167KB) ( 445 )   Under the action of bearing load, the relative slip at interface between steel beam and concrete of a composite beam affects greatly its bearing capacity, deformation and resistance to shock. In order to evaluate correctly the load-bearing performance of a prestressed steel composite beam with high-strength concrete, the equivalent cross-sectional area and virtual work principle are taken into account to derive the calculation formulas of deformation of the composite beam according to actual loading conditions, including all interactions between different forces and the effect of slip at interface. Analyzes the effect of relative slip at interface on the deformation of the composite beam under symmetric concentrated load and/or uniform load. The calculated result is verified in good conformity with test result, and shows that the slip at interface can increase the deformation of the composite beams by over 10 percent. References | Related Articles | Metrics

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- - 2005, 26 (7):  703-706.  DOI: - Abstract ( 216 )   HTML   PDF (326KB) ( 652 )   - References | Related Articles | Metrics

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Magnon softening of two-dimensional triangular insulating ferromagnet at finite temperature Cheng, Tai-Min (1); Du, An (1); Xianyu, Ze (1) 2005, 26 (7):  707-710.  DOI: - Abstract ( 216 )   HTML   PDF (188KB) ( 494 )   A magnon-phonon interaction model is developed on the basis of two-dimensional triangular insulating ferromagnet. The magonon spectrum is studied through Matsubara-Green function, and the magnon dispersion curve is calculated on the main symmetric point and line in Brillouin zone for different parameters in the system. It is concluded that at the boundary of Brillouin zone magnon linewidth broadening and magnon softening are both enhanced. The influences of longitudinal and transverse phonon on magnon spectrum softening and linewidth broadening are compared and discussed, as well as the influences of other relevant parameters and temperature change. The following conclusions are thus drawn: (1) The closer the magnons come to the boundary of Brillouin zone, the more intense the magnon-phonon coupling and the clearer the magnon softening; (2) The vibration of magonon spectrum is irrelevant to the intense of magnon-phonon coupling; (3) The smaller the stiffness constant of spin and the lower the Debye temperature ΘD of the material, the clearer the magnon softening; (4) Below the transition temperature (Tc) of ferromagnetic, the higher the temperature, the clearer the magnon softening; (5) On the Σ line (including the point Γ, M) and Z line (including the point M , K) , the longitudinal phonon have greater influence on magnon softening than the transverse one. References | Related Articles | Metrics

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Ground state properties of Ising metamagnet in transverse field Liu, Jing (1); Wei, Guo-Zhu (1); Gu, Yong-Wei (1); Zhang, Qi (1) 2005, 26 (7):  711-714.  DOI: - Abstract ( 255 )   HTML   PDF (165KB) ( 571 )   The ground state properties of the two-sublattice Ising metamagnet in the transverse field are studied introducing the mean-field theory. A phase diagram is given via the h-Ω rectanguler coordinates where h is the longitudinal field and Ω is the transverse field. The ground state energy, the longitudinal total magnetization, staggered magnetization and susceptibility and the transverse total magnetization are all calculated. The results show that when the transverse field Ω is small but the longitudinal field h great, the first-order transition occurs, and when the former is great but the later small the second-order transition occurs in the system. The effect of the transverse field Ω on the ground state properties of the two-sublattice Ising metamagnet is important. References | Related Articles | Metrics