Loading...

Table of Content

    25 May 2007, Volume 35 Issue 5
    Previous Issue    Next Issue
    Electronics, Communication & Automation Technology
    Information Encryption Algorithm Based on Multiple Chaotic Mappings
    Liu lin-mei Qiu Shui-sheng Xiang Fei Xiao Hui-juan
    2007, 35(5):  1-5. 
    Asbtract ( 262 )   PDF (364KB) ( 999 )  
    Related Articles | Metrics

    In order to improve the security of chaotic encryption , a dynamic encryption algorithm based on multiple chaotic mappings is proposed. In the proposed algorithm , two cascaded chaotic subsystems composed of simple chaotic mappings are adopted , and their outputs are added to the plaintext with modulus to obtain encrypted information. The iterations of the subsystems are randomly changed , so that the unpredictability of the encrypted information is enhanced. Simulation tests and security analyses show that the proposed algorithm possesses large key space , high sensitivity to plaintext and key , and excellent security against varied attacks via statistical and differential characteristics and phase space reconstruction.

    Fuzzy LMS Algorithm Dominated by ELSE-Action
    Li Wei-jun Yu Qing-jun Xie Sheng-li
    2007, 35(5):  6-9. 
    Asbtract ( 256 )   PDF (232KB) ( 543 )  
    Related Articles | Metrics

    In order to overcome the incomplete inference mechanism and great computational complexity in FSSLMS algorithm , a new fuzzy LMS algorithm dominated by ELSE-action is presented. In the presence of an ELSE rule , the inference mechanism can be successfully executed with slight computational complexity in any input data conditions. As compared with other fuzzy LMS algorithms , the proposed algorithm is better because it constructs a simpler and more reliable fuzzy rule. Experimental results show that the proposed algorithm is of not only less computational complexity but also better perfonnances than other fuzzy LMS algorithms and other conventional LMS algorithms.

    Predictive Frame Refreshment ßased on Scene-Context Reference Frame
    Ai Yu-hua Ye Wu Feng Sui-li Hu Bing Xie Ming
    2007, 35(5):  10-14. 
    Asbtract ( 297 )   PDF (341KB) ( 574 )  
    Related Articles | Metrics

    In order to avoid the error propagation due to packet loss and bit error during the video transmission in wireless network , a novel error-resilient scheme with predictive frame refreshment is proposed based on scene-context reference frame. By segmenting the video sequences , the corresponding predictive frames locating at the original frames and needing to be intra-frame refreshed are predictably coded based on the scene-context reference frame within the same scene scope. The predictive frame refreshment is then implemented by means of the scene-flag and refresh-signal synchronization between the encoder and the decoder. As compared with the traditional intra-frame refreshment method , the proposed scheme can obviously reduce the frame bit rate with a similar reconstructed video quality when the video transmits over an unreliable wireless network that requires high intra-frame refreshment rate.

    Frequency-Domain Resolution and Its Improvement During Empirical Mode Decomposition
    Hu Wei-ping Mo Jia-lini Du Ming-hui
    2007, 35(5):  15-19. 
    Asbtract ( 377 )   PDF (332KB) ( 309 )  
    Related Articles | Metrics

    The main task of Empirical Mode Decomposition (EMD) is to offer the monocomponents or narrow band signals prior to Hilbert transform. During the EMD , the frequency band of intrinsic mode function (IMF) is rather wide due to the mode mixing and the signal interaction. In order to solve this problem , the band width of IMF resulting from a single EMD is investigated , and the corresponding instantaneous frequency resolution is calculated ,
    on the basis of which an improved signal masking method is proposed to narrow the frequency band of signal before the standard EMD. Experimental results show that the proposed method can not only overcome the mode mixing in EMD completely but also avoid the disadvantages caused by the signal interaction , thus effectively improving the frequency-domain resolution expressed by IF after the Hilbert transform of IMF.

    Evaluation AIgorithm of Fingerprint Quality ßased on Feature Fusion
    Ma Li-hong Yu De-cong Lu Han-qin Chen Zhi-qing
    2007, 35(5):  20-24. 
    Asbtract ( 308 )   PDF (371KB) ( 552 )  
    Related Articles | Metrics

    In order to solve the problem of quality difference in fingerprint in public security fingerprint database , a new fusion method to evaluate fingerprint quality is proposed by combining the spatial and the frequency features of a fingerprint image. In this method , the black-pixel ratio in the central area , the ring structure of Fourier spectrum and the directional Gabor features are first employed to respectively assess the fingerprint quality , and their corresponding evaluation performances are discussed. Then , according to the evaluation capacities of these features for different quality images , a nonlinear fusion approach is presented to obtain the final quality scores by weighing the nonlinear fusion of the features mentioned above. The fusion criterion is finally tested in a public security fingerprint database , the results demonstrate that the proposed nonlinear fusion algorithm is feasible in fingerprint quality evaluation.

    Cone-Beam Reconstruction Range Based on R-Iine Algorithm
    Li Zhen-zhen Du Ming-hui
    2007, 35(5):  25-29,40. 
    Asbtract ( 279 )   PDF (394KB) ( 755 )  
    Related Articles | Metrics

    The reconstruction ranges of various cone-beam source trajectories are mathematically described based on the R-line algorithm , and the definition and existence of the reconstruction ranges are studied. Then , the section characteristics of the reconstruction ranges of several typical trajectories such as orthogonal double circles , helix and saddle trajectories are investigated. The effect of trajectory discretization on the reconstruction accuracy is finally discussed. Experimental results show that the sets of reconstructed points are controlled by the geometric parameters of the reconstruction range , and that the reconstructed points after the trajectry discretization non-uniformly distribute with an uneven reconstruction error distribution.

    Pre-Integrated Volume Rendering Based on Shear-Warp
    Li Bin Tian Lian-fang Chen Ping Mao Zong-yuan
    2007, 35(5):  30-34. 
    Asbtract ( 251 )   PDF (304KB) ( 582 )  
    Related Articles | Metrics

    In order to improve the quality of the 3 D medical image reconstructed via Shear-W arp , an improved pre-integrated volume rendering (IPVR) algorithm based on Shear-Warp is proposed , in which the volume rendering equation and the light model are adopted to determine the final re-sampling value and to construct an intermediate image. Thus , the aliasing artifacts resulting from the under-sampling in the standard Shear-W arp algorithm can be avoided by the pre-integrated volume rendering technology. Experimental results demonstrate that the proposed method meets the requirement of real-time volume rendering with good display performance.

    Skew Correction of Railway Ticket Images Based on Hough Transform
    Liang Tian-cai Pi You-guo Peng Jing Zhu Zhao-hua
    2007, 35(5):  35-40. 
    Asbtract ( 313 )   PDF (400KB) ( 1084 )  
    Related Articles | Metrics

    In order to implement the skew correction of images in the anti-false and auto-checking system for railway ticket , a method of the skew correction is proposed based on Hough transform. In the proposed method , the objective information of the ticket images is extracted from the background according to the attribute of railway ticket images and the existing algorithm of skew detection , and the horizontal trajectories are smoothed before picking up the characteristic line of text. Theh , multi-stage Hough transform is adopted to determine the skew angle , and the line fitting technique is used to correct the skew images. Experimental results verify the effectiveness and reliability of the proposed algorithm.

    Augmented Reality Registration AIgorithm ßased on Natural Feature
    Zhao Xin-Can Zuo Hong-fu
    2007, 35(5):  41-45. 
    Asbtract ( 232 )   PDF (326KB) ( 646 )  
    Related Articles | Metrics

    In the augmented reality registration algorithm of fiducial points , many artifical markers are added in the real scene , which makes the system veηcomplex. In order to solve this problem , a robotic visual servo system is analyzed , and an augmented reality registration algorithm based on natural feature with virtual visual servo technology is proposed. Then , by taking the geometrical characters including point and moment as the image characters ,matrices describing the interaction between the variation of image character and that of virtual relative pose , namely , the Jacobian matrices of the image , are presented , by which a 3D registration algorithm based on natural feature is achieved. As compared with the hybrid tracking and the coplane four-point registration algorithms , the proposed algorithm is of higher registration accuracy.

    A Novel Microstrip Patch Rectenna with 5. 8 GHz
    Deng Hong-lei Kong Li
    2007, 35(5):  46-49,64. 
    Asbtract ( 233 )   PDF (330KB) ( 1568 )  
    Related Articles | Metrics

    As the microstrip patch rectenna is light and is of large inception area , it is very suitable for the microwave power transmission in microwave plane and high flat , where the requirement for weight is serious. In this paper, a novel microstrip patch rectenna with 5. 8 GHz is introduced , and its parameters are optimized with the help of simulating softwares such as IE3D VlO. 0 and ADS 2003C. It is proved from experiments that the structure is feasible and a high rectification efficiency of 78.2% can be reached.

    Judgment on Consistency of Blind Source Separation Outputs with Source Signals
    Yao Zhi-xiang Liu Huan-bin Su Hui
    2007, 35(5):  50-53. 
    Asbtract ( 319 )   PDF (251KB) ( 913 )  
    Related Articles | Metrics

    In the blind source separation (BSS) , it is necessarγto judge whether the BSS outputs are consistent with the source signals. In this paper , based on the statistical independence of statistical independence variable functions , a method to judge the consistency of the outputs in independent component analysis (ICA) with the source signals is presented. In this method , the correlation matrix of two mixing matrices which respectively belong
    to the source signals and the source differences is calculated , and the consistencies of the independent components with the source signals are then judged according to the maximum correlation coefficients corresponding to each independent component. Simulated and experimental results indicate that the independent components are consistent with the corresponding source signals when the maximum correlation coefficients converge 1 , and that the maximum correlation coefficient should not be less than O. 8 to ensure the separation accuracy.

    Computer Science & Technology
    SeveraI EssentiaI Laws Required by Modern Network Traffic
    Chen Yun-long Ye Wu Feng Sui-li
    2007, 35(5):  54-59. 
    Asbtract ( 297 )   PDF (373KB) ( 587 )  
    Related Articles | Metrics

    In order to model the modern network traffics in multi-time scales which enables the parameters to have physics meanings , the basic characteristics of the long-range dependence (LRD) in network traffics are investigated, and several essential laws required by modern network traffics are proposed. The relationships among the parameters such as Cγor cf that describes the quantitative LRD , the traffic aggregated level m and the average arrival rate λ in long-range dependence traffic are then revealed , followed by verification with real measured data. The proposed laws include the opinions that there exists LRD in network traffics indeed , certain statistically-quantitative relationships between the average arrival rate involving the TCP and IP levels , etc. and the parameter Cγ or Cf .

    Extension and Realization of Dynamic Power Management Architecture
    Liu Fa-gui Mai Wei-peng Huang Kai-yao
    2007, 35(5):  60-64. 
    Asbtract ( 343 )   PDF (335KB) ( 780 )  
    Related Articles | Metrics

    In the traditional dynamic power management (DPM) architecture , positive policies are generally adopted without considering the great power consumption due to power state transitions , and the policy optimization is not taken into account. This paper aims at the above-mentioned problem and extends the original DPM architecture by adding two modules , namely , the system workload detecting and policy optimizing modules. Several examples are then performed to implement the policy optimization algorithm on the new architecture , which reveals the feasibility and flexibility of the proposed extended architecture.

    Novel Algorithm for K-Nearest Neighbors of Massive Data Based 00 Spacial Partitioo
    Ping Xue-lian Xu Rong-li Kong lun Liu Sheng-lan
    2007, 35(5):  65-69. 
    Asbtract ( 269 )   PDF (356KB) ( 863 )  
    Related Articles | Metrics

    In the reverse engineering , the first thing for processing the measured data is to build up the topology of the point cloud , which is generally implemented by calculating the K-nearest neighbors. In this paper , the existing algorithms of K-nearest neighbors are analyzed , and a new algorithm for K-nearest neighbors of massive data based on spacial partition is proposed. In the proposed algorithm , the effects of K value and point-cloud density and number on the side length of small sub-cubes are considered , and the most suitable searching range is obtained by finding the suitable side length of small sub-cubes and by excluding small sub-cubes without point cloud inside. Thereby , the searching speed is raised and the correctness of searched results is ensured. The proposed algorithm is finally verified by the second exploiting programming of reverse engineering software.

    Dynamic Mean-LEL Portfolio Selection Model
    Guo Fu-hua Deng Fei-qi
    2007, 35(5):  70-74,80. 
    Asbtract ( 237 )   PDF (352KB) ( 527 )  
    Related Articles | Metrics

    This paper aims at a dynamic portfolo selection prob1em via the optimization method. Firstly , in the standard Black -Scholes financial market , the dynamic mean -limited expectation loss (LEL) portfolio selection model is established , in which the risk of portfolio is measured by the LEL. Secondly , the explicit expressions for the optimal portfolio strategy and the mean-LEL efficient frontier are obtained. Finally , the method of solving the model is illustrated by a numerical example. It comes to the conclusion that the value at risk (VaR) is about 2 - 10 times that of LEL under the same expected terminal wealth and portfolio strategy.

    Random I/O Performance of Buffer Scheduling Algorithm for Tape Library
    Wu tao Yang Jie
    2007, 35(5):  75-80. 
    Asbtract ( 237 )   PDF (394KB) ( 494 )  
    Related Articles | Metrics

    In order to improve the on-line storage efficiency of magnetic tape , a buffer scheduling algorithm for tape library is put forward ， in which the medium changer is virtualized as a logical block device and the disk drive is used as a buffer. An active write-back method and a data prefetching strategy are then presented to manage the random I/O process orderly and to improve the random I/O performance. Besides , the performance of the algorithm is ana-lyzed in detail and a simulation is performed to test the algorithm. The results demonstrate that the proposed algorithm greatly deduces the aggregate and single I/O response time.

    Mining Algorithm for Multi-Level Fuzzy Association Rules Based on SOFM Network
    Li Xue-jun Li Long-shu Xu Yi
    2007, 35(5):  81-85. 
    Asbtract ( 357 )   PDF (363KB) ( 588 )  
    Related Articles | Metrics

    In order to represent a complex large concept hierarchy tree , this paper proposes a more general coding scheme which applies concept hierarchy into the mining of fuzzy association rules. As it is difficult to determine the membership function subjectively , a self-organizing feature map (SOFM) network is introduced to determine the membership function of sample data. Based on the improved coding scheme and the SOFM network , fuzzy set is then introduced to design a new algorithm of mining multi-level fuzzy association rules. Experimental results show that the proposed algorithm is of high efficiency and scalability and can effectively mine multi-level fuzzy association rules that are meaningful and easily understandable.

    Periodic Sequences with Large 2-adic and κ-error 2-adic Complexities
    Dong Li-Hua Hu Yu-pu Zeng Yong
    2007, 35(5):  86-89. 
    Asbtract ( 319 )   PDF (252KB) ( 568 )  
    Related Articles | Metrics

    According to the theory of stream ciphers in cryptology , the 2-adic complexity and. the κ-error 2-adic complexity similar to other complexity measures must have large values. In this paper , the relationship between the linear complexity and the 2-adic complexity is investigated based on the Chinese Remainder Theorem and some other related theories in the number theory , and the existence of N-periodic sequences that simultaneously achieve the maximum 2-adic complexity and a great κ-error 2-adic complexity is proved. Then , a lower bound of the number of the N-periodic sequences with such properties is given. The existence of many such sequences can effectively thwart the attacks against the keystreams by exhaustive search.

    A Database Model Based on P2P System
    Yu Mei Zhao Zheng Yu Jian
    2007, 35(5):  90-93,99. 
    Asbtract ( 273 )   PDF (329KB) ( 841 )  
    Related Articles | Metrics

    In order to overcome the botùeneck node in the distributed database system in client/ server mode and to reduce the network transfer load for keeping the data consistency between nodes , a local relation model (LRM) of database based on P2P system is proposed , and the theoretic semantics and architecture of LRM are presented. Moreover, an instance is presented to analyze the data transfer according to domain relation and the way to the realization of coordination formulas between P2P nodes. It is finally concluded that the proposed LRM helps to reduce the data communication between nodes , improve the system reliability and provide flexible sharing on data and service.

    Chemistry & Chemical Engineering
    Thermodynamic Analysis of Microcline-CaSO4 -CaCO3 System
    Shi Lin Chen Ding-sheng
    2007, 35(5):  94-99. 
    Asbtract ( 332 )   PDF (361KB) ( 644 )  
    Related Articles | Metrics

    In order to produce soluble potash fertilizer by means of calcination , the thermodynamic analysis and ex-perimental research about the pyrolysis reaction of microcline-CaSO4 -CaCO3 system were carried out. The results in-dicate that , for CaO-SiO2 , CaO-Al2O3 , SiO2-Al2O3 and CaO-SiO2-Al2O3 systems , 2CaO • SiO2 and 2CaO • Al2O3 • SiO2 will first generate in CaO-rich area during the process of solid-phase thermal decomposition reaction , and that the calcined products will further transfer into 2CaO • SiO2 and 3CaO • Al2O3 with the increase of CaCO3 content. According to such a trend , the best molar ratio of microcline: CaSO4 : CaCO3 is 1: 1: 14 , which is further validated by experiments.

    Relationship Between Preparation Process and Resistivity of ZnO Semiconductor Powder
    Wu lian-qing Zhong Yi yan Dong-liang
    2007, 35(5):  100-103,108. 
    Asbtract ( 262 )   PDF (328KB) ( 767 )  
    Related Articles | Metrics

    ZnO semiconductor powders doped with Al2O3were synthesized via solid synthesis. The inf1uences of Al2O3 doping content , calcination temperature and soaking time on the resistivity of ZnO powders were then analyzed by means of XRD. Experimental results show that ZnAl2O4 spinel may exist in ZnO semiconductor powders and the electric conductivity may decrease when the doping content of Al2O3 overruns O. 5 % in molar ratio , and that ZnO powders with low resistivity can be obtained when enough Al3+ enter the ZnO crystal lattice at a certain calcinations temperature for a certain soaking time. However , excessive calcination temperature and soaking time may result in the formation of ZnAl2O4 spinel from Al2O3 and ZnO , which makes the replacing ratio of Al3+ for Zn2+ decrease and the electron scattering occur, thus increasing the resistivity of ZnO powders. It is also indicated that the synthesized ZnO powders are of a resistivity of 18kΩ•cm when the reaction system is calcined at 1300℃ for 3 h with a Al2O3 doping content of O.5% .

    Performance of Trivalent and Hexavalent Chromium Passivation Films Based on Zinc Plating
    Zeng Zhen-ou Zou lin-guang Zhao Guo-peng Liu lian-ping
    2007, 35(5):  104-108. 
    Asbtract ( 259 )   PDF (435KB) ( 601 )  
    Related Articles | Metrics

    In order to replace the hexavalent chromium in passivation solution with trivalent chromium and achieve pollution-free production for zinc plating , the cOITosion resistances , electrochemical behaviors , heat-resistant abilities and microstructures of trivalent and hexavalent chromium passivation films were studied via neutral salt spray (NSS) test , Tafel plot curves and SEM. The results of NSS test show that trivalent chromium passivation film can
    pass 84 h of NSS test and possesses better cOITosion resistance than the hexavalent one. The Tafel plot curves indicate that trivalent chromium passiva.tion film is of a lower cOITosion rate but a higher heat-resistant ability than the hexavalent one. Moreover , the SEM micrographs show that trivalent chromium passivation film is compact even after heat treatment , while the microstructure of hexavalent chromium passivation film is loose reticular.

    Effect of Cerium on Performance of Cu -Based Zr Pillared Clay Catalyst
    Dong Xin-fa Cao Yi-qian Lin Wei-ming
    2007, 35(5):  109-112. 
    Asbtract ( 295 )   PDF (270KB) ( 496 )  
    Related Articles | Metrics

    The clay pillared by multi-oligomeric hydroxyl cation was used to synthesize Zr-RE-PILC (RE = Ce , La ,Y) supports , and was treated by SO42-. Then , Cu-based pillared clay catalyst Cu/Zr-RE-PILC with a Cu massfraction of 3% was prepared by means of impregnation. Moreover , the catalytic performance of Cu/Zr-RE-PILC for the selective reduction of NO by propylene in the presence of Ce , La and Y was investigated in a micro reactor.XRD was finally adopted to characterize the catalyst. The results indicate that both the catalytic activity for the selective reduction of NO and the thermal stability of the supports at a high temperature can be improved by introducing Ce in the catalyst , that Zr-Ce-PILC support with excellent thermal stability can be synthesized in a Zr/ Ce ratio ( molar ratio) of 5 at an aging temperature of 65 "C and a calcination temperature of 500 ℃ , and that , when the
    feed composition is 0. 22% NO-0.15% C3 H62% O2 -97.63% He and the space velocity is 50000 mL/ (h•g)  , the NO conversion reaches 65% at a reaction temperature of 300℃, and reaches 22.5% even at a reaction temperature of 500℃ over Cu/Zr-Ce-PILC catalyst.

    Preparation and Properties of New-Type Porous Thermal Insulation Material
    Gao Xue-nong Wang Duan-yang Huang Huo-yang Fang Yu-tang
    2007, 35(5):  113-116,131. 
    Asbtract ( 316 )   PDF (353KB) ( 1149 )  
    Related Articles | Metrics

    Based on the micro-scale heat and mass transfer mechanism , a new-type porous thermal insulating material was prepared hy means of microwave heating and expanding , with expanded perlite as the aggregate , sodium silicate as the adhesive , and calcined kaolin , CaCO3 and Li-hentonite as the additives. The effect of heating and expanding method on the performance of the prepared material was then analyzed , and the variation of thermal conductivity with component proportion was investigated. The results indicate that the optimal mass ratio of expanded perlite/ sodium silicate/Li -hentonite/ calcined kaolini CaCO3 is 46: 36: 13: 3: 2 , that the contents of expanded perlite and sodium silicate are two main factors influencing the thermal conductivity of the product , and that the additions of Li-hentonite , calcined kaolin and CaCO3 can effectively improve the mechanical strength and water resistance of the prepared porous thermal insulating material.

    Modificaion of Wheat Straw Alkali Lignin by Oxidation and Sulfomethylation
    Liang Wen-xue Qiu Xue-qing Yang Dong-jie Lou Hong-ming
    2007, 35(5):  117-121. 
    Asbtract ( 324 )   PDF (348KB) ( 487 )  
    Related Articles | Metrics

    In order to improve the water solubility and increase the relative molecular mass of wheat straw alkali lignin (W AL) , the modification of W AL by oxidation and sulfomethylation was carried out with F enton agent as the oxidant and sodium sulfite as the sulfonating agent. The charge density distributions of the structural elements of aromatic groups in lignin and hydroxymethylignin were analyzed based on the molecular orbital theory，finding out that the possible position of sulfomethylation is C-5 in guaiacyl suit. Then , sulfomethylignin was obtained by the sulfomethylation of WAL after the oxidation. FTIR results show that the product exhibits a typical absorption of sulfomethylate group. The conductometric titration reveals that the content of sulfomethylate group is 0. 96 mmol / g.Moreover , a methoxyl content of 5.41 % and a Mw value of 6653 are respectively measured by the Ziesel method and GPC , and a surface tension of 45. 3 mN/m at a solution mass concentration of 30 g/L is measured. A similar dispersion of the product to that of calcium lignosulfonate in cement slurry is finally revealed by fluidity test.

    Preparation of Hydrogen Peroxide by Eco-Friendly Electrolysis
    Xu Ke-feng Li Zhong Li Hua-liang Xia Qi-bin
    2007, 35(5):  122-125. 
    Asbtract ( 365 )   PDF (269KB) ( 1191 )  
    Related Articles | Metrics

    Hydrogen peroxide was prepared by means of electrolysis in an electrolytic cell with activated carbon fiber cloth as the cathode and titanium electrode coated with lrO2•RuO2 (Ir-Ru/Ti) as the anode. The influences of voltage , pH value and air flowrate on the production efficiency were then analyzed , and the effects of titanium electrode and Ir-Ru /Ti electrode on the hydrogen peroxide production performance were compared. The results show that Ir-Ru/Ti anode can greatly increase the peroxide yield and enhance the stability of peroxide production in comparison with the titanium anode , that peroxide can be efficiently produced by electrolysis in both acidic and neutral conditions , that the peroxide concentration increases with the air flowrate , that the voltage has great influence on the peroxide production with a suitable value , and that a hydrogen peroxide concentrat,ion of 8.18 x10-4 mol/L can be achieved in a neutral solution without any chemical addition after 90-min electrolysis at a voltage of 20V and an air flowrate of 80 mL / min.

    Effect of Emulsifier on Kinetics and Nucleation Mechanism of Semi -Continuous Emulsion Polymerization
    Sun Zhi-juan Zhang Xin-ya Jiang Qing-mei Huang Hong Chen Huan-qin
    2007, 35(5):  126-131. 
    Asbtract ( 283 )   PDF (402KB) ( 835 )  
    Related Articles | Metrics

    Acrylate emulsions were prepared hy means of semi -continuous emulsion polymerization , and the influence of emulsifier concentration [E] on the polymeric kinetics and nucleation mechanism was investigated. Then , the evolvement of particle size distrihution with [E] in the whole polymerization process was analyzed. Experimental results show that the polymerization rate Rp ∝[E]1.28 and the nucleation mechanism of the system is "micellar nucleation" when [E] is more than 0.01 mollL , whereas Rp ∝[E]0.17 and the main nucleation mechanism is "homogeneous nucleation" when [E] is less than 0. 01 mol/L. Furthermore , the particle size distribution of emulsions in the whole polymerization process proves that the nucleation mechanism varies with the value of [E].

    Preparation of Ibuprofen Solid Lipid Microparticles
    Zhang Li-juan Liu Lei Long Chun-xia Yan Hong
    2007, 35(5):  132-136. 
    Asbtract ( 292 )   PDF (340KB) ( 310 )  
    Related Articles | Metrics

    Ibuprofen solid lipid microparticles (SLMs) were prepared by means of high-shear emulsification , and the effects of emulsification temperature , cooling temperature , stirring rate and initial drug content on the performance of SLM were investigated. The results show that the mean diameter of SLM slightly decreases and the monodispersity becomes better with the increase in emulsification temperature and stirring rate and with the decrease in cooling temperature , that the entrapment efficiency of ibuprofen in SLM becomes greater in low emulsification and cooling temperatures , and that the initial drug content has little effect on the mean diameter , the monodispersity and the entrapment efficiency. Moreover , it is found that , in the optimal conditions , namely , an emulsification temperature of 85 ℃ , a cooling temperature of 5  ℃, a stirring rate of 12000 r/min and an initial drug content of 10% , ibuprofen SLM with good monodispersity and a prolonged drug release time from 3 h to 12 h can be prepared , and the mean diameter and entrapment efficiency achieve (3.81 ±0. 12)μm and 91. 35% ±1. 18% , respectively.

News
 
More>>
Featured Article
More>>
Most Read
More>>
Most Download
More>>
Most Cited
More>>
Links
More>>