Archive

15 December 2007, Volume 28 Issue 12 Previous Issue    Next Issue
---
OriginalPaper


For Selected:

Download Citations EndNote Ris BibTeX

Toggle Thumbnails

OriginalPaper

Select

Improved fuzzy-smith approach for active queue management He, Ling (1); Zhang, Nan-Nan (1); Yang, Mu-Yi (1); Jing, Yuan-Wei (1) 2007, 28 (12):  1673-1676.  DOI: - Abstract ( 247 )   HTML   PDF (406KB) ( 675 )   The transmission delay brings about disadvantages of congestion control in network, while the relevant existing algorithm depends on the exactitude of model excessively. A new active queue algorithm is thus proposed by improving Smith estimate compensator in combination with fuzzy control, which is link up with TCP. The improved Smith estimate compensator can control more timely the TCP congestion, and fuzzy controller can get rid of an exact model for the object to control. In this way, the advantages of Smith estimate compensator and fuzzy controller may complement each other. The results of numerical example show the validity of such a tactical combination. References | Related Articles | Metrics

Select

Synchronization of chaotic systems using terminal sliding mode control Yan, Min-Xiu (1); Jing, Yuan-Wei (1) 2007, 28 (12):  1677-1680.  DOI: - Abstract ( 247 )   HTML   PDF (250KB) ( 618 )   A terminal sliding mode controller of a class of second-order chaotic systems is studied on the basis of drive-response synchronization. The finite time synchronization of chaotic systems is realized by designing a continuous terminal sliding mode controller with an improved sliding surface introduced to get rid of the singularity phenomenon resulting from improper choice of parameter. Simulation results showed that the modified terminal sliding controller will not only reduce the chattering effectively but also improve the track ability and steady accuracy of the system, thus enabling the finite-time synchronization of chaotic systems to come true. References | Related Articles | Metrics

Select

Improved Canny algorithm for edge detection Lu, Zhe (1); Wang, Fu-Li (1); Chang, Yu-Qing (1) 2007, 28 (12):  1681-1684.  DOI: - Abstract ( 337 )   HTML   PDF (405KB) ( 1856 )   Because of the high similarity between the gradient magnitudes of low-contrast edge and noise, the conventional Canny algorithm for detection, which is based on the double-threshold to detect and connect edges, damages partly the low-contrast edge though it suppresses noise. An improved Canny algorithm is therefore proposed instead of the double-threshold one, which detects and connects the edges in accordance to the difference of the gradient direction between the edge and the noise, so as to protect efficiently the details of all low-contrast edges with the noise suppressed simultaneously. The new approach is thus superior to the conventional one. Simulation tests have verified the effectiveness of the improved Canny algorithm for edge detection. References | Related Articles | Metrics

Select

Multiloop feedback control strategy for high-performance single-phase power supply through sinusoidal inverter Chen, Hong-Zhi (1); Liu, Xiu-Chong (1); Qian, Xiao-Long (1); Yan, Shi-Jie (1) 2007, 28 (12):  1685-1688.  DOI: - Abstract ( 227 )   HTML   PDF (258KB) ( 855 )   A multiple feedback loop control scheme is presented for single-phase power supply through sinusoidal inverter. The proposed outer control loop uses two PI controllers for the independent control as magnitude/phase to ensure a highly steady precision of the voltage output from inverted power supply. The inner control loop uses voltage output as a feedback to ensure a fast response to the voltage output and reduce waveform distortion. A new algorithm is proposed to detect the phase of sinusoidal voltage output from the inverted power supply so as to make the high-precision control of power supply inversion easy to implement. The simulation results verify that the control system based on the proposed method has excellent dynamic/static characteristics to keep all voltage output waveforms highly sinusoidal under any loading conditions. References | Related Articles | Metrics

Select

Uniform design based method of T-S modeling Li, Yan (1); Mao, Zhi-Zhong (1) 2007, 28 (12):  1689-1692.  DOI: - Abstract ( 228 )   HTML   PDF (152KB) ( 646 )   T-S fuzzy system is widely applied to different data-based modeling methods. As the core of T-S system, the fuzzy rule sets is the most important factor to the precision and generalization of the system, but the number of fuzzy rules is very difficult to determine. Taking account of how these rules are generated in view of cluster subtraction, the cluster radius (CR) affects the number of rules directly. Thus, the uniform design is chosen to set the cluster radius so as to determine the number of rules easier and simplify the modeling of complex multi-variable system. The effectiveness of the method proposed is verified through a simulation example. References | Related Articles | Metrics

Select

Design and simulation based on fuzzy self-adaptive PID for secondary cooling control system during continuous casting Liu, Wen-Hong (1); Wang, Biao (1); Ma, Jiao-Cheng (1); Xie, Zhi (1) 2007, 28 (12):  1693-1696.  DOI: - Abstract ( 378 )   HTML   PDF (838KB) ( 577 )   To improve billet quality and the trackability and stability of secondary cooling water during continuous casting, the tundish temperature is introduced into the water distribution for secondary cooling to design the relevant control system, based on the distribution model, tundish temperature, surface temperature and fuzzy self-adaptive PID. A spray cooling system is thus set up for simulation in lab to test the step signal from the conventional, integral separated and fuzzy self-adaptive PID controllers and the simulated casting. The simulation results show that the fuzzy self-adaptive PID controller's performance is better than the other two controllers', which provides a foundation for further study and application. References | Related Articles | Metrics

Select

Design of strong pulsed magnetic field stimulator for cardiomuscle Liu, Chun-Ling (1); Xu, Bin (1); Wang, Xu (1); Du, Yu-Yuan (1) 2007, 28 (12):  1697-1700.  DOI: - Abstract ( 215 )   HTML   PDF (1097KB) ( 1014 )   A strong pulsed magnetic field stimulator was designed successfully and made for cardiomuscle to study the biomagnetic effect on heart. An electromagnetic field with magnetic induction up to 10.6 Tesla can be obtained at the center of its exciting coil when the DC charging voltage is 1200 V. The method to calculate the induction is given. An open chest frog was stimulated by the pulsed magnetic field with magnetic induction 2.7 T at 0.2 Hz, and the result showed that its heart rate is restored after a fluctuation caused by the stimulator. References | Related Articles | Metrics

Select

Application of self-tuning-fuzzy PID algorithm in hydraulic turbine governor Zhao, Hai (1); Song, Chun-He (1); Han, Xu-Dong (1); Zhu, Peng (1) 2007, 28 (12):  1701-1704.  DOI: - Abstract ( 245 )   HTML   PDF (200KB) ( 686 )   Fuzzy PID algorithm has been widely applied to industrial process control, extraction of fuzzy rules, proportion, quantizing factors and membership function are all determined subjectively to certain extent in fuzzy controller design. An improved fuzzy adaptive PID algorithm (IFPID) is thus proposed, using PSO algorithm to optimize the preprocessed membership function. Comparing the simple PID algorithm with the conventional fuzzy PID algorithm, in a simulation test of turbine governor, the proposed algorithm shows shorter regulating time and smaller overshoots when the system is disturbed by response frequency and load fluctuation. References | Related Articles | Metrics

Select

Performance of space-time block code in time-varying fading channel Sha, Yi (1); Men, Jin-Ling (1); Wang, Jing-Wu (2); Wang, Guang-Xing (1) 2007, 28 (12):  1705-1708.  DOI: - Abstract ( 246 )   HTML   PDF (327KB) ( 785 )   The performance of STBC (space-time block code) in time-varying fading channel is studied with its practicability in focus. A simulation model in time-varying fading channel is developed using SIMULINK, which consists a channel, transmitting end and receiving end. Further, the channel comprises a multipath Rayleigh channel and Gaussian white noise, the transmitting end comprises signal source, serial-parallel converter, modulator, STBC and power dividing block and the receiving end comprises signal combiner, maximum likelihood decoder, modem and BER computing block. Simulating results indicated that in a flat and slowly fading channel the performance of STTD (space-time transmit diversity) is much better than it in single transmitting/receiving case and can be improved quickly with increasing SNR. But, if in a flat time-varying fading channel, the performance of STTD degrades with increasing maximum Doppler shift especially in case of high SNR. References | Related Articles | Metrics

Select

Microstructure and properties of C-SiC-B4C composites prepared by hot pressing sintering (II): Oxidation behavior Yu, Liang (1); Ru, Hong-Qiang (1); Cai, Ji-Dong (1); Zuo, Liang (1) 2007, 28 (12):  1709-1712.  DOI: - Abstract ( 210 )   HTML   PDF (677KB) ( 649 )   C-SiC-B4C-TiB2 composites were hot pressed at 2000°C with graphite flake, SiC, B4C and TiO2 as raw materials. The oxidation behavior of C-SiC-B4C-TiB2) composites in steady atmosphere at 600-1400°C was analyzed in view of isothermal oxidation with oxidation mechanism studied through TG/DTA thermal analysis, and XRD and SEM were used for the phase composition and cross-sectional morphology of oxide layer. The results showed that the oxidation kinetic curves of the composites are in form of parabola. No matter what content of graphite flake is the oxide layer comprises oxide film and transition layer. The composite with 20% graphite flake content has an excellent oxidation resistance with self-reduction properties at 1400°C and forms a compact oxide film which is composed of TiO2 or SiO2·TiO2 solid solution that has not become glass yet and its morphology shows dendritic structure. References | Related Articles | Metrics

Select

Comparison of texture and properties of IF steel with ELC steel Guo, Yan-Hui (1); Wang, Zhao-Dong (1); Li, Shou-Wei (1); Zou, Wen-Wen (1) 2007, 28 (12):  1713-1716.  DOI: - Abstract ( 329 )   HTML   PDF (583KB) ( 807 )   The microstructure, texture and mechanical properties of an ELC steel and an IF steel both produced by hot rolling in ferrite region, cold rolling and annealing were compared. The results showed that deformation bands are dominant in the ELC while equiaxed grains grow in the IF after hot rolling in ferrite region. The hot band texture of ELC includes not only strong α-fiber but weak γ-fiber, while that of IF is mainly the γ-fiber. However, after cold rolling and annealing, ELC presents mainly the γ-fiber texture with peak at {111} <112> , and IF presents the strong and well-proportioned γ-fiber texture which provides obviously higher strength than ELC. Moreover, the values of mean plastic strain ratio and percentage elongation of IF are 0.6 and 5% higher than ELC, respectively, with higher tensile strength and lower yield strength provided. References | Related Articles | Metrics

Select

Temperature-stress coupling computation and warping analysis for controlled cooling of plate Zhou, Na (1); Wang, Bing-Xing (1); Wu, Di (1); Zhang, Dian-Hua (1) 2007, 28 (12):  1717-1720.  DOI: - Abstract ( 229 )   HTML   PDF (351KB) ( 708 )   Based on the boundary conditions of heat convection on plate surface during header cooling, a numerical simulation was done using the software ANSYS in combination with indirect temperature-stress coupling computation for the temperature field and stress/strain field in three different cooling processes. Comparing the different temperature-time histories and stress-strain curves on plate's cross section as resulting from simulation, the plate warping deformation due to three different cooling modes was analyzed. The results showed that the alternate cooling with big and small headers benefits the decrease in the temperature gradient along plate thickness, and the temperature gradient affects unobvious the plate warping. The cooling homogeneity on plate's top and bottom surfaces are the main cause for plate warping. The conclusion will provide a theoretical foundation to control the cooling process for plates. References | Related Articles | Metrics

Select

Crystallization behavior of glass-ceramics prepared from boron mud Shi, Pei-Yang (1); Zhang, Da-Yong (1); Wang, Yuan-Yuan (1); Jiang, Mao-Fa (1) 2007, 28 (12):  1721-1724.  DOI: - Abstract ( 233 )   HTML   PDF (920KB) ( 572 )   According to the characteristics of the composition of boron mud, ferrous tailing and fly ash as raw materials, the crystallization behavior of glass-ceramics in different mixture ratios was studied systematically. The results showed that, with the increasing boron mud the initial crystallizing temperature of such glass ceramics lowers, and the principal crystalline phase is hedenbergite. When the boron mud component comes to 30%-40% in mixture ratio, the crystal distribution become relatively uniform. Transforming the crystal form from branch to ball can improve the properties of glass ceramics. References | Related Articles | Metrics

Select

Effect of rolling-bonding process on structure and mechanical properties of aluminum foam sandwich Zu, Guo-Yin (1); Hao, Liang (1); Zhang, Min (1); Yao, Guang-Chun (1) 2007, 28 (12):  1725-1728.  DOI: - Abstract ( 257 )   HTML   PDF (1145KB) ( 675 )   The process technology combining rolling-bonding technique with powder metallurgic foaming to prepare AFS (aluminum foam sandwich) was studied. Discusses the effect of the process technology applied to both face plate and core powder on the powder compactness, and it in relation to foaming effect. The foaming mechanism of AFS through the rolling-bonding process was found preliminarily. The results showed that the rolling process can provide very high compactness of core powder which decreases greatly the loss of H2 released from the foaming agent TiH2 in AFS during foaming. Thus, the foaming power is so sufficient that the defects such as bubble-free layer and large-size connected holes hardly occur. When the content of TiH2 is 1wt% the ideal foaming structure can be got after rolling-bonding and foaming processes to decrease production cost. AFS thus made has high flexural strength and other better mechanical properties as verified by three-point tests. References | Related Articles | Metrics

Select

Preparation of TiB2 coating and its corrosion resistance to electrolyte Ban, Yun-Gang (1); Yang, Shao-Hua (1); Kan, Hong-Min (1); Wang, Zhao-Wen (1) 2007, 28 (12):  1729-1732.  DOI: - Abstract ( 250 )   HTML   PDF (450KB) ( 793 )   TiB2 coating was electrodeposited on graphite substrate from K2TiF6-KBF4-KF-KCl-LiF molten salts at 820°C for 3 hr with a current density 0.7 A/cm2, of which the composition of the electrolyte used is 15 K2TiF6, 24 KBF4, 48KF, 8KCl, 5LiF in wt%. The penetration of sodium and electrolyte into the TiB2 coating used as cathode of aluminum electrolysis was studied. After electrolysis for 4 hr, the SEM analysis showed that Na, F and Al penetrated slightly into the TiB2 coating, and XRD pattern showed that there is a little NaF in the graphite substrate. Compared with graphite cathode, TiB2 coating can slow up. sodium formation and decelerate sodium penetration, but can not hinder sodium from penetration thoroughly. References | Related Articles | Metrics

Select

Access control model for computer-supported collaborative design system Xu, Hong-Xue (1) 2007, 28 (12):  1733-1736.  DOI: - Abstract ( 237 )   HTML   PDF (267KB) ( 705 )   The existing access control models are imperfect to meet the requirements for a collaborative design system nowadays. Based on the characteristics of collaborative design and RBAC (role-based access control) model, a new model named MDACM (message-driven access control model) is developed to solve security problem due to the distributivity and dynamic ability of collaboration through an authority that is expressed by a message entity or integrated message entity in combination with filter rule, then control by static allocation. Moreover, the workflow control base is introduced into the model to affect message entity and support the workflow management of computer-supported collaborative design system. An application as example is given to demonstrate the effectiveness of the model. References | Related Articles | Metrics

Select

Novel STFT of window duration increasing optimization based on instantaneous frequency Li, Yun-Gong (1); Yao, Zhao (2); Liu, Jie (1); Liu, Jing-Tao (1) 2007, 28 (12):  1737-1740.  DOI: - Abstract ( 265 )   HTML   PDF (382KB) ( 633 )   What role the window function plays in time-frequency analysis and the shortcoming of S transform are discussed. It is revealed that the result of the analysis is affected greatly if the window is narrow or the window duration is adjusted according to the analysis frequency. Based on STFT, a new method of time-frequency analysis is presented, where the window duration is adjusted automatically according to the time-varying characteristic of signal. Taking the change of instantaneous frequency as the criterion for the change of signal spectrum structure, the method can increase window duration before the change of instantaneous frequency so as to cause the window to cover the whole or majority of local stationary signal, thus obtaining the optimum time-frequency resolution for all local of stationary signal. The method proposed applies to analyzing and comparing the chirp signal, time-varying signal and the noisy overlapped signal. The results show that it can exactly represent the time-frequency distribution of signal with optimum time-frequency resolution obtained, and is non-sensitive to noise. The method is therefore regarded as advanced and practical. References | Related Articles | Metrics

Select

FEM simulation of initial cracking process due to thermal fatigue Yan, Ming (1); Sun, Zhi-Li (1); Yang, Qiang (1); Chen, Feng-Xi (2) 2007, 28 (12):  1741-1744.  DOI: - Abstract ( 398 )   HTML   PDF (499KB) ( 1236 )   The process and rules of the initial cracking due to thermal fatigue are studied considering the multi-linear kinematic hardening of material, with a simple sample as model analyzed by FEM. During the half cycle of warming the crack is closing and its two wall surfaces extrude each other because of thermal expansion. Then, the plastic compressive deformation comes into being when the compressive stress reaches the yield limit. During the half cycle of cooling, the sample tends to restore its original shape. However, because the plastic compressive deformation formed before cannot come back, the crack opens gradually. One of the necessary conditions of the initial cracking due to thermal fatigue is that the material on high temperature side has been deformed compressively and plastically, which is different from the cracking due to common fatigue. References | Related Articles | Metrics

Select

Structure and tribological properties of a-C:H films deposited by RF PECVD Li, Ming (1); Lin, Zeng (1); Wang, Feng (1); Ba, De-Chun (1) 2007, 28 (12):  1745-1748.  DOI: - Abstract ( 501 )   HTML   PDF (382KB) ( 1198 )   The hydrogenated amorphous carbon (a-C:H) thin films were successfully deposited on stainless steel substrate by radio frequency plasma enhanced chemical vapor deposition (RF PECVD). The microstructure and morphology of the film were investigated by means of Raman spectroscopy, X-ray photoelectron spectroscopy, infrared spectrometry and atomic force microscopy. The friction and wear behavior of the film sliding against a stainless steel ball under different loads and at different velocities were examined on a pin-on-disc tester. It was found that the film prepared by RF PECVD has typical hydrogenated diamond-like characteristics and is very smooth and compact, and it shows good friction-reducing and wearable behavior when sliding against a stainless steel ball. The results also revealed that the films wearability is in relation to the graphite transfer film formed on the worn surface and the graphitization of the film in tribological process. References | Related Articles | Metrics

Select

Fragmentation methods of Nocardia cell and its IR spectral analysis Wei, De-Zhou (1); Jia, Chun-Yun (1); Cao, Cheng-You (2); Liu, Wen-Gang (1) 2007, 28 (12):  1749-1753.  DOI: - Abstract ( 284 )   HTML   PDF (266KB) ( 623 )   The fragmentation of Nocardia was investigated by ultrasonic method and cell autolysis, and both could fragment well the microbe. But, the latter requires longer time than the former. The total time required and power output are the key influencing factors of ultrasonic method, and frequent short-time fragmenting steps and 1.5 g/L bacterium density are beneficial to cell fragmentation. In the cell autolysis process, time is the key factor, and that the NaCl density is 1% and temperature at 50°C is beneficial to cell autolysis in which the collaborative effect of all enzymes in Nocardia is better when pH value is 7-9. The result of IR spectral analysis indicated that the categories of radicals found in cell walls after either ultrasonic method or cell autolysis are almost the same. References | Related Articles | Metrics

Select

Effect of Ni3Si coating on resistance to NaCl/O2/H2O synergic corrosion behavior of Ti6Al4V alloy Yu, Cun-Zhen (1); Wei, De-Zhou (1); Zhu, Sheng-Long (2) 2007, 28 (12):  1754-1757.  DOI: - Abstract ( 268 )   HTML   PDF (525KB) ( 507 )   The effect of Ni3Si coating deposited by magnetron sputtering on the synergic anticorrosion behavior of the alloy Ti6Al4V was investigated at 600°C. The results showed that Ni3Si coating possesses excellent resistance to the synergic corrosion due to water vapor, O2 and NaCl because of the SiOx formation on the coating surface in corrosion process, while the alloy suffers from catastrophic corrosion, including not only the inner oxidation but also lots of corrosive products flaking off without the coating. The anticorrosion behavior of the alloy and coating were studied using scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), X-ray diffraction (XRD), electron probe microanalysis (EPMA) and X-ray photoelectron spectroscopy (XPS), with the anticorrosion mechanisms of the coatings discussed. References | Related Articles | Metrics

Select

SOD effect of cadmium chloride on acute toxicity of grass carp Wang, Gui-Yan (1); Hu, Xiao-Min (1); Zhou, Qi-Xing (2); Sun, Xue-Qi (3) 2007, 28 (12):  1758-1761.  DOI: - Abstract ( 318 )   HTML   PDF (105KB) ( 791 )   The acute toxicity of cadmium chloride to grass carp was investigated by stagnophile testing, as well as the effect of superoxide dismutase systems (SOD) on grass carp's liver, kidney and gill tissues. The results showed that the LC50 for grass carp are 45.58, 34.81, 28.63 and 24.05 mg·L-1 when the acting time of acute toxicity of cadmium chloride are 24, 48, 72 and 96 h, respectively. The high ecological toxicity of cadmium is thus proved to grass carp. The activity of SOD in grass carp's liver and kidney tissues decreases first then increases and decreases once again when Cd2+ presents low concentration pollution, while the activity of SOD is inhibited obvious all along (p<0.05) when Cd2+ presents high concentration pollution. However, the activity of SOD in grass carp's gill tissues decreases first then increases when Cd2+ presents low concentration pollution, while the activity decreases first then increases and then decreases once again when Cd2+ presents high concentration pollution. It was revealed that the activity of SOD in grass carp's gill tissues is much lower than in liver and kidney tissues. References | Related Articles | Metrics

Select

Comparative study on growth of four varieties of Spirulina platensis and their hydrogen release behavior Li, Quan-Shun (1); Xu, Cheng-Hai (1); Jia, Qing-Shu (2); Peng, Run-Ling (1) 2007, 28 (12):  1762-1765.  DOI: - Abstract ( 332 )   HTML   PDF (650KB) ( 728 )   A comparative investigation was done experimentally for four varieties of Spirulina platensis, covering their growth conditions and hydrogen release behavior. The aim is to explore in depth the utilization of the hydrogen release from Spirulina platensis as energy resources. The result indicated that different varieties of Spirulina platensis require different optimal growth conditions and that their hydrogen releases are different greatly in both time required and quantity. A conclusion is thus drawn that the variety screening and improvement can be regarded as the mean to increase the hydrogen releasing quantity from Spirulina platensis. References | Related Articles | Metrics

Select

Dynamic response and liquefaction potential of large-size ash stacked dam Li, Ming (1); Liang, Li (1); Zhao, Jun (1); Wang, Chang-Jian (1) 2007, 28 (12):  1766-1769.  DOI: - Abstract ( 253 )   HTML   PDF (489KB) ( 654 )   Discusses the relationships between stress and strain, dynamic modulus and dynamic strain and the degree ratio of liquefaction to stress and number of cycles of destructive vibration in view of the fly ash consolidation with liquid drained (CD) and undrained (CU) to which the triaxial tests of fly ash samples taken from a stack yard of a petrochemical plant were done statically and dynamically. The finite element software ANSYS was applied to the static analysis of the heightened ash stacked dam and the dynamic response of a tailing dam under the action of Park Field seismic wave. A liquefaction analysis was made to the ash stack yard by way of shear stress correlation. The results showed that the relative density of fly ash (Dr) affects greatly the area of liquefaction region, i.e. the smaller the Dr the bigger the area. A conclusion is drawn that the control of Dr is indispensable to the liquefaction stability of ash stacked dam. References | Related Articles | Metrics

Select

Evaluation of high rock slope quality based on theory of extenics Kang, Zhi-Qiang (1); Zhou, Hui (2); Feng, Xia-Ting (1); Yang, Cheng-Xiang (1) 2007, 28 (12):  1770-1774.  DOI: - Abstract ( 289 )   HTML   PDF (112KB) ( 813 )   A forecasting method is proposed for the high rock slope stability of Longtan hydropower station, based on the matter element model as deduced from the theories of extenics. The elements in classical and sectorized field are defined using the stability classification and influencing factors on rock slope, then an extension forecasting model is developed for comprehensive evaluation of the classification of rock slope stability by the correlation function of matter elements and extension sets. The forecasting results are thus obtained through such an evaluation. An exemplification shows that the method proposed can forecast the classification of rock slope quality more accurately and scientifically, thus providing a more reliable basis for taking economic and reasonable supporting/reinforcing measures. References | Related Articles | Metrics

Select

On the explosion proof of magnesium powder in view of its sensitivity to ignition Li, Gang (1); Zhong, Ying-Peng (1); Yuan, Chun-Miao (1); Chen, Bao-Zhi (1) 2007, 28 (12):  1775-1778.  DOI: - Abstract ( 287 )   HTML   PDF (132KB) ( 1078 )   The main technological processes for magnesium powder production are reviewed. The sensitivity to ignition was tested for four kinds of magnesium powder of which the D50 included 6, 47, 104 and 173 μm, as well as the minimum ignition energy (MIE) and minimum ignition temperature (MIT). Respectively, the MIE test results for the four samples are <2, 260, 300 mJ and >2000 J, and the MIT values for relevant dust clouds are 480, 520, 620°C and higher than 700°C. With respect to the MIT of a dust layer, all the values are higher than 450°C. Then, the risk of conventional technological processes of magnesium powder production and their possible ignition sources are discussed in a perspective of the sensitivity to ignition. References | Related Articles | Metrics

Select

TOPSIS method to solve group decision problems with preference information in ordinal interval form Fan, Zhi-Ping (1); You, Tian-Hui (1) 2007, 28 (12):  1779-1781.  DOI: - Abstract ( 245 )   HTML   PDF (128KB) ( 650 )   For the group decision making problems with alternative preference information in form of ordinal interval, a TOPSIS (technique for order preference by similarity to ideal solution) method is proposed to analyze the decision making process. Describing such problems, a distance formula is given between two random ordinal intervals. Then based on the conventional TOPSIS method, the calculation steps are given to solve group decision making problems with ordinal intervals, where the key point is using the distance formula given above to calculate the distance(s) between each and all alternatives and the positive or negative ideal solution and, further, the alternatives are ranked in accordance to the relative closeness coefficient of every alternatives calculated. A numerical example is given to illustrate the feasibility and effectiveness of the proposed method. References | Related Articles | Metrics

Select

Multi-attribute decision making in view of degree of preference for part of alternatives Guo, Ya-Jun (1); Yi, Ping-Tao (1) 2007, 28 (12):  1782-1785.  DOI: - Abstract ( 235 )   HTML   PDF (234KB) ( 692 )   During multi-attribute decision making, it is difficult to assign weights directly for all attributes, and decision makers therefore prefer offering the relevant information for part of alternatives. How to use partly the alternative preference information to make decision is studied, of which the basic process is to use G1-method to convert the language information into data information. Then, a programming model is developed to approach the idea about decision and, by solving the model, the optimum weights are obtained. The method is very simple to use and embodies the integration of instinctive decision making with scientific decision making. An example is given to illustrate the effectiveness of the proposed method. References | Related Articles | Metrics

Select

- - 2007, 28 (12):  1786-1790.  DOI: - Abstract ( 248 )   HTML   PDF (207KB) ( 1239 )   - References | Related Articles | Metrics

Select

- - 2007, 28 (12):  1791-1794.  DOI: - Abstract ( 212 )   HTML   PDF (181KB) ( 836 )   - References | Related Articles | Metrics

Select

Influence of the slight structural variation on elastic constants of chromites spinel Li, Mei-Ling (1); Sun, Feng-Jiu (1) 2007, 28 (12):  1795-1798.  DOI: - Abstract ( 247 )   HTML   PDF (357KB) ( 842 )   According to the first principles, the lattice structure, elasticity and electronic properties of three kinds of chromites spinel subject to slight structural variation are studied by the pseudowaves plane (PWP) approach based on density functional theory (DFT) and generalized gradient approximation (GGA). The calculated and experimental results are compared and show that the values of lattice constant, bulk module and shear module are all in good agreement. The slight structural variation enables the bulk modulus to decrease considerably and the Young's modulus increases clearly with increasing coordinate value of atomic oxygen, but the shear modulus and Poisson ratio decreases substantially. It is concluded that the electron exchange action between iron and chromium actions is the main influencing factor on the variation of the elasticity after analyzing the electronic properties such as DOS (density of states), the most nearest-neighboring bond lengths between Fe/Cr actions and O anion and electronic populations. References | Related Articles | Metrics

Select

Beam current simulation of plume from nitrogen plasma gun in atmosphere Yu, Han-Jiang (1); Sun, Feng-Jiu (1); Zhang, Jun (1) 2007, 28 (12):  1799-1802.  DOI: - Abstract ( 196 )   HTML   PDF (1050KB) ( 446 )   To provide a theoretic foundation for industrial plasma applications, in locally thermodynamic equilibrium, the beam current from a nitrogen plasma gun was simulated in atmosphere, through solving the RNG k-Ε equation, and difference grid. The shape of beam current was thus got and it was basically in conformity to that measured in simulation. The temperature field of the plasma beam current was calculated on the condition of different gas flux, with the shape of beam current found through plotting its boundary at 600 K. The results showed that when the gas flux F<0.8 m3/h, the size of beam current decreases with decreasing gas flux, and when F>0.8 m3/h, the size distribution of beam current tends to be stable. If so, a better plasma source is available to plasma applications. It was verified the best size range of beam current for plasma applications is 7-8 mm which is also the maximum one. References | Related Articles | Metrics