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Table of Content

    25 June 2015, Volume 43 Issue 6
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    Chemistry & Chemical Engineering
    Adsorption Property and Sacrificial Effect for Tertiary Oil Recovery of Lignin Derivatives
    Qiu Xue-qing Zhang Zhi-ming Yang Dong-jie Huang Kai Zhou Ming-song
    2015, 43(6):  1-8.  doi:10.3969/j.issn.1000-565X.2015.06.001
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    By investigating the influences of pH value，urea and inorganic salts on the adsorption property of sodium
    lignosulfonate (SL) on calcium carbonate (CaCO3)，it is found that the electrostatic interaction and the hydro-gen bondingare not the main adsorption driving forces of SL adsorption on CaCO3 surface，and that the salts with strong complexation ability as well as the blocking of some carboxyl groups of SL with lithium chloride may decrease the adsorption capacity of SL，which means that the complexation between the carboxyl of SL and CaCO3 is the main adsorption driving force． Moreover，by using carboxymethylated lignin (CAL) with high carboxyl content (2. 59mmol/g) as a sacrificial agent in tertiary oil recovery，it is found that CAL is of outstanding sacrificial effect even at low mass concentration，with a maximum sacrificial effect value being up to 95. 15%; and that both CAL and SL possess good compounding effect with sodium dodecyl benzene sulfonate．

    Distribution Regularity of Residence Time in Flatted Reactor Radiated by Multi-Frequency Ultrasonic
    Zou Hua-sheng Lü Xue-ying Li Xue-feng
    2015, 43(6):  9-14.  doi:10.3969/j.issn.1000-565X.2015.06.002
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    Flatted ultrasonic reactor is the core component of the continuous biodiesel production equipment． As a reflection of the flow pattern，the back-mixing degree and the reaction effect，the residence time distribution (RTD) is significant to the design，manipulation and control of flatted ultrasonic reactors． In this paper，the RTD curves were obtained through measuring the outlet KOH concentration of the flatted multi-frequency ultrasonic reac-tor with a pHB-3 type pH tester in real time，with KOH solution as the tracer in the pulse method and with purified water as the main fluid． Then，the contributions of ultrasonic power and fluid flow to the flow condition and non-ideality of the fluid in the reactor were investigated，and a fitting of the experimental data was performed by using a continuous-flow stirred tank reactor (CSTR) model． The results show that，under the action of 200W ultrasonic，the theoretical number of series kettles is respectively 6. 06 and 6. 76 when the flow rate is respectively 20 and 30L/h; and that，at a high flow rate，the simulation effect becomes better and the flow pattern most likely tends to plug flow．
    Analysis of Pyrolysis Mechanism of 5-Hydroxymethyl Furfural by Using PY-GC-MS and In-Situ FT-IR
    Liao Yan-fen Guo Zhen-ge Cao Ya-wen Ma Xiao-qian Lin Yan
    2015, 43(6):  15-21.  doi:10.3969/j.issn.1000-565X.2015.06.003
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    Pyrolysis experiments of 5-hydroxymethyl furfural (5-HMF) were conducted and the product composi-tion was detected by using a PY-GC-MS analyzer． The results show that nearly 86% of the pyrolysis product is fu-ran ring-contained substance，and that a certain amount of small molecules exist in the product，which means that the pyrolysis process of 5-HMF is mainly a side-chain degradation process concomitantly with the fracture of furan rings． Moreover，the converting law of the product in the pyrolysis process was supervised in real time via in-situ FT-IR． The results show that furfural and 5-methyl furfural mainly form when the temperature ranges from 130 to 230℃，furfuryl alcohol and 5-formyl-2-furfurylacetate mainly form after 250 ℃ and the formation continues to the middle and later periods of the whole process，while the dominant pyrolysis product of 5-HMF，namely furan-2，5-dicarbaldehyde，forms throughout the whole pyrolysis process． According to the results obtained from fast pyrolysis experiment and in-situ FT-IR，the pyrolysis mechanism is speculated as follows: as the most primary reaction，fu-ran-2，5-dicarbaldehyde forms from two consecutive dehydrogenations and then converts into 5-methyl furfural after the dehydroxylation and hydrogenation of hydroxymethyl; the whole fracture of hydroxymethyl side chain and alde-hyde group side chain leads to the formation of furfural and furfuryl alcohol; and 2-methylfuran may be produced via the secondary pyrolysis of furfural and furfuryl alcohol．
    Theoretical Investigation into Pyrolysis Behaviors of α-O-4 Lignin Dimer
    Wu Shu-bin Liu Chao Deng Yu-bin
    2015, 43(6):  22-29,36.  doi:10.3969/j.issn.1000-565X.2015.06.004
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    In order to reveal the depolymerization mechanism of α-O-4 linkages in lignin during the process of py-rolysis，phenolglycerol-α-phenyl ether is selected as the α-O-4 lignin dimer mold compound，and its pyrolysis behaviors at 773K and 101kPa are simulated according to the density functional theory (DFT)． Then，the enthalpy changes of each step are calculated． It is found that the dimer pyrolysis starts from the dissociations of Cα —O and Cα —Cβ bonds． According to the thermodynamics possibility，the following pyrolysis is designed into differentpaths，and the final pyrolytic products are found to contain small molecule compounds (methanol，ethanol，ethylene glycol and ethylene oxide)，phenol and para-substituted phenols (p-methyl phenol，p-ethyl phenol and p-hydroxybenzyl alcohol)，benzene and substituted benzene (benzyl alcohol)． In all these phenolic compounds，p-methyl phenol and p-ethyl phenol are the most possible products，which are followed by phenol． In addition，the pyrolysis behaviors of α-O-4 and β-O-4 lignin dimers are compared． The results show that all the differences between the two lignin dimers are attributed to their different structures．
    Effect of Preimpregnation with Ionic Liquid Microemulsion on Enzymolysis Efficiency of Eucalyptus
    Yang Ren-dang Li Long Yang Fei
    2015, 43(6):  30-36.  doi:10.3969/j.issn.1000-565X.2015.06.005
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    The effects of the composition，impregnation mode and treatment condition of alkali-strengthened DILMS (Double Ionic Liquid Microemulsion) on the enzymatic hydrolysis efficiency of eucalyptus were discussed，and the variation of monose content in the residue and the impregnation liquid was analyzed． Moreover，the increment of glucose in the enzymatic hydrolysis process was quantitatively investigated by means of the ion chromatography． Finally，suitable DILMS impregnation conditions，that is，a temperature of 100 ℃，an impregnation duration of 8 h and a substrate size of 40 meshes (namely a diameter of 180 ～380μm)，were determined． Experimental results indicate that，by using the alkali-strengthened quadrol (70℃，3h) impregnation with the DILMS preimpregnation，the glucose proportion in the total reducing sugar increases from 64. 33% to 96. 34%，the enzymatic hydrolysis efficiency improves from 35. 8% to 83. 2%，the actual yield of glucose is 2. 11 times that of the untreated raw mate-rial． It is thus concluded that the alkali-strengthened DILMS is effective in improving the preimpregnation efficiency．
    Effects of Different Carbon Aerogel Conductive Agents on Performance of Li-MnO2 Battery
    Yang Wei Chen Sheng-zhou Xue Jian-jun Hu Xin-fa Xia Xin-de Lin Wei-ming
    2015, 43(6):  37-41.  doi:10.3969/j.issn.1000-565X.2015.06.006
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    Carbon aerogel was prepared by means of the sol-gel method from resorcinol and formaldehyde through CO2 supercritical drying，freeze drying and ambient drying，and the resistivity and pore structure of the product were characterized via N 2 low-temperature adsorption desorption，four-probe method and SEM． Moreover，the influence of carbon aerogel conductive agent on the high-rate discharge performance of Li-MnO2 battery was investigated． The results indicate that (1) the carbon aerogels produced via different drying methods are of similar resistivity but distinctly different specific surface areas; (2) the carbon aerogel prepared via CO2 supercritical drying possesses the highest specific surface area (1017. 85m 2 /g) and the largest constant-current specific discharge capacity (101mAh/g at a current of 100mA); (3) the voltage plateau of the carbon aerogel prepared via CO2 supercritical drying is 80mV higher than that prepared via ambient drying; and (4) there is little difference in the 1 mA discharge capacity of different carbon aerogels． All these above-mentioned statements show that carbon aerogel conductive agents possess higher performance than the commercial acetylene black．
    Mechanical Engineering
    Three-Dimension Modeling of Manufacturing Plant Scene Based on RGB-D Sensor
    Quan Si-bo Li Wei-guang Zheng Shao-hua
    2015, 43(6):  42-47.  doi:10.3969/j.issn.1000-565X.2015.06.007
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    Environment perception is a prerequisite for the autonomous intelligent operation of automatic guided ve-hicles，and 3D maps are more suitable than the 2D ones for representing an unstructured scene． However，the existing laser radar-and vision-based methods both have some deficiencies． In this paper，a ＲGB-D sensor mounted on a mobile robot with open-source ＲOS framework is used to build an integrated system for the three-dimension modeling of large-scale and complex scenes in manufacturing plants，and the architecture of hardware and ＲOS software modules of the system as well as the scanning strategy is introduced． Moreover，an experiment is carried out to investigate the automatic continuous scanning of a region in a manufacturing plant scene，the data registration and the three-dimension modeling of the system． The results show that the proposed system meets the requirements of three-dimension scene modeling well．
    Theoretical Model and Eigen Solutions of Cylindrical Magnetorheological Fluid Couplings
    Wang Gong-xian Zhang Yu Hu Zhi-hui Zhou Peng-zhong
    2015, 43(6):  48-55.  doi:10.3969/j.issn.1000-565X.2015.06.008
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    A nonlinear system dynamics model of cylindrical magnetorheological fluid (MRF) couplings，which considers such properties as the maximum transmission torque，the adjustable torque multiple，the phase difference of angular velocity，the stabilization time and the designed coupling dimension，is established，and the dominant eigen solutions reflecting the property indicators of the couplings is presented． Based on the eigen solutions，the dimension and properties of a MRF-132DG coupling are designed and evaluated． The results show that the proposed theoretical model and eigen solutions possess definite physical meanings，thus avoiding complicated numerical analysis of mathematical models and complex curve fitting of experimental property parameters． This research provides direct guidance and reference for the design and property analysis of MＲF couplings with the structure similar to MRF-132DG．
    Control Strategy of Modal Space for a Hydraulically-Driven Stewart Platform Considering Passive Joint Damping
    Tian Ti-xian Jiang Hong-zhou Huang Qi-tao He Jing-feng Tong Zhi-zhong Nie Bo-xun
    2015, 43(6):  56-62,70.  doi:10.3969/j.issn.1000-565X.2015.06.009
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    In order to overcome the system over-damping caused by the conventional hinged form commonly-used in parallel manipulators in industry，a modal space controller with positive pressure feedback is presented． In this controller，the highly-coupled multiple-input multiple-output systems in the physical space are transformed into six independent single-input single-output decoupled systems in the modal space，and the positive pressure feedback technology is employed to tune each degree of freedom (DOF) with over-damping independently and to broaden the bandwidth of each DOF to the eigenfrequencies． In the investigation，first，the influence of passive joint damping on the control characteristics of a hydraulically-driven Stewart platform is analyzed based on the modal decoupling theory． Then，the structure and the design method of the modal space controller with pressure feedback are presented． Finally，an experiment is carried out to testify the effectiveness of the proposed controller． The results indicate that the designed modal space controller effectively broadens the system bandwidth，thus reducing the coupling effect between each two DOFs and improving the response speed．
    Analysis of Dynamic Bifurcation and Stability of Gear System with Multiple Clearances and High Contact Ratio
    Li Fa-jia Zhu Ru-peng Jin Guang-hu Bao He-yun Ye Fu-min
    2015, 43(6):  63-70.  doi:10.3969/j.issn.1000-565X.2015.06.010
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    In this paper，a dynamic model of straight spur gear system with high contact ratio (HCR)，multiple clearances and time-varying meshing stiffness was established，the energy equations of the model were established based on the principle of work and power，the meshing stiffness of the gear system was calculated by means of finite element method，and the dynamic bifurcation and jump characteristics of the system were investigated by using the Runge-Kutta method． The results show that (1) there are abundant dynamic bifurcation characteristics in the HCR gear system influenced by multiple clearances; (2) with the increase of rotation speed，single-period，multi-period and chaotic motions appear in the system，and the motion state jumps from chaos to period motion in a crisis manner; (3) there is an obvious jump in the chaotic area; (4) the backlash greatly affects the system; for instance，the motion state is periodic when the backlash is less than 3. 85 × 10－5 mand is chaotic in most areas when the backlash is larger than 3. 85 ×10-5m; (5) the motion state of the gear system is in the crisis area of chaotic and periodic motions at low damping ratios and may get into single-period stable state via the channels of reversing bifurcation at high damping ratios; and (6) the driven clearance greatly affects the motion state of the system，while the driving clearance only has little influence on the motion state．
    Out-of-Plane Stability of Crane Jib with Double Ｒods Considering Flexibility of Fixed Joint
    Wang Teng-fei Lan Peng Lu Nian-li
    2015, 43(6):  71-76.  doi:10.3969/j.issn.1000-565X.2015.06.011
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    Proposed in this paper is an analytical method for the out-of-plane stability analysis of crane jib with double rods． In this method，the effect of lateral flexibility of the fixed joint on the jib stability is considered，and a dimensionless lateral stiffness coefficient is introduced to measure the lateral constraint． Then，by establishing the deformation differential equation in the critical state，the characteristic equations of out-of-plane instability and the corresponding critical force are deduced． It is found that the analytical results are completely consistent with the ANSYS simulation results． Moreover，the expressions of the characteristic equations，respectively in two limited lateral stiffness conditions of the fixed joint and in the degradation case of the jib to single rod，are discussed，and the influence of lateral stiffness of the fixed joint on the stability of the jib is analyzed． The results show that a suitable increment of the lateral stiffness may significantly improve the stability of the jib until the lateral stiffness reaches a certain value．
    Contact Stress Analysis and Crowning Design of Friction Pair with Rollers Under Misalignment and Skewing Conditions
    Chen Xiao-yang Zhou Yue Shen Xue-jin Wang Zhi-jian Zhang Xiao-ling Ma Chun-qing
    2015, 43(6):  77-83.  doi:10.3969/j.issn.1000-565X.2015.06.012
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    Based on the static elastic-contact theory，a model to describe the mechanical contact between the roller and the race is established under misalignment and skewing conditions，and the fast Fourier transform (FFT) and the conjugate gradient method are employed to obtain the elastic deformation and the contact stress，respectively．Then，the influences of different parameters on the contact stress distribution are analyzed． The results show that (1) at a constant skewing angle，both the misaligned load effect and the edge effect remarkably improve with the increase of the misalignment angle; (2) at a constant misaligned angle，the skewing phenomenon becomes more obvious with the increase of the skewing angle，and the misalignment angle helps to weaken the edge effect caused by the contact between the roller and the inner race，while the misaligned load effect and the skewing phenomenon both become worse when the roller is contacted with the outer race; and (3) with the increase of the length-to-dia-meter ratio，both the misaligned load effect and the skewing phenomenon become more obvious． In addition，a crowning design method considering both the misalignment and the skewing of the roller is presented to improve the anti-misalignment and anti-skewing ability of roller bearings．
    Three-Parameter Weibull Distribution of Machining Center Based on ITLS and DE
    Wang Xiao-feng Zhang Ying-zhi Shen Gui-xiang Long Zhe Zhang Li-min
    2015, 43(6):  84-88.  doi:10.3969/j.issn.1000-565X.2015.06.013
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    In order to solve the problems existing in the parameter estimation of three-parameter Weibull distribu-tion，an improved total least square (ITLS) method is proposed for parameter estimation，and a differential evolu-tion (DE) algorithm is adopted for parameter optimization． DE helps to accurately and rapidly find a global optimal solution of the objective function in the optimization process，and ITLS helps to obtain realistic and reasonable re-sults because it considers not only the independent but also the dependent variables during the regression analysis．At the same time，by taking the square sum of deviations as the constraint rule，ITLS helps to achieve the best curve fitting effect with higher authenticity． The proposed method is then used to establish a three-parameter Weibull distribution model of a machining center，and the results are compared and analyzed． Analytical results show that the proposed method effectively improves the accuracy and authenticity of the reliability model of machi-ning centers and thus provides an effective method for the reliability modeling of the complete appliance．
    Effects of Cooling/Lubrication Conditions on Surface Integrity of Pure Iron Materials During Turning
    Kong Jin-xing Deng Fei Zhao Wei He Ning
    2015, 43(6):  89-95.  doi:10.3969/j.issn.1000-565X.2015.06.014
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    In order to improve the surface quality of pure iron materials during the finishing turning，some experi-ments were carried out at the same cutting parameters under such four cooling/lubrication conditions as dry cutting，water-based cooling，rapeseed oil lubrication and minimum quantity lubrication (MQL)，and the influence mecha-nisms of cooling/lubrication conditions on the surface integrity of the pure iron workpiece were analyzed． The re-sults indicate that (1) as compared with the dry cutting and the water-based cooling，the MQL and the rapeseed oil lubrication are more advantageous to the improvement of the surface roughness of the workpiece; (2) the surface microhardness varies in the same trend under different cooling/lubrication conditions，and the depth of hardened layer is about 60 ～70μm; (3) the surface grains show severe tensile and distorted plastic deformation，and the dry cutting results in the deepest deformation while the water-based cooling results in the shallowest deformation; and (4) the surface residual stresses in the tangential and the axial directions are both tensile and insensitive to coo-ling/lubrication conditions，and the tangential stress is larger than the axial one． These experimental results are of great significance for selecting suitable cooling/lubrication conditions to improve the surface integrity of pure iron materials during the finish turning．
    Design of Precision Inverter Power Supply for Micro Arc Welding
    Yang Kai Cao Biao Liu Han-bo
    2015, 43(6):  96-102.  doi:10.3969/j.issn.1000-565X.2015.06.015
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    In order to improve the control precision of welding current and the stability of arc with low current du-ring the micro arc welding，a precision inverter power supply is designed． In this power supply，a digital control system based on the digital signal processor is introduced into the traditional argon tungsten arc welding inverter，and the limited bipolar control method is used to realize the soft switching of the full-bridge inverter． In addition，the electrical characteristics of the arc load are introduced，the requirements of welding process for the power su-pply are analyzed，two kinds of waveform control schemes respectively for direct current and pulse are designed，and the software procedure of the power system and the corresponding control algorithm are expounded． It is de-monstrated that both the precise control of output energy and the nice consistency of waveforms can be achieved by accurately controlling such output parameters as current，time，frequency and pulse width; and that the integral separation PID control algorithm helps to realize a smooth transition of the arc from arcing to breakdown and then to annihilation，thus improving the stability of arc with low current．
    Mechanics
    Application of Improved Calculation Method of Ｒayleigh Damping Coefficient to Seismic Ｒesponse Analysis of Quay Crane Structure
    Li Zhe Wang Gong-xian Hu Yong Hu Ji-quan
    2015, 43(6):  103-109,121.  doi:10.3969/j.issn.1000-565X.2015.06.016
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    As the Ｒayleigh damping coefficient remarkably influences the time-history analysis accuracy of the seis-mic response of quay crane structures，an improved calculation method of Ｒayleigh damping coefficient is proposed．In this method，both the spectrum characteristics of the ground motion and the frequency characteristics of the structure itself are taken into consideration，which makes the calculation more reasonable． Then，a series of dynam-ic time-history analyses of quay crane structures are performed by using different calculation methods of damping co-efficient，and the results are compared with those obtained by the shaking table test． It is found that，under differ-ent seismic wave excitations，when the numerical calculation results are closest to the test ones，different damping coefficient calculation methods are adopted; and that the time-history calculation results of quay crane structures ob-tained by the improved method under various seismic response accord well with the experimental ones．
    CEL Algorithm-Based Analysis of Dynamic Characteristics of Amphibious Aircraft Landing on Water
    Yao Xiao-hu Huang Yu-tai Ou Zhi-cheng Liu Xiao-ming Hu Bo-ren
    2015, 43(6):  110-115.  doi:10.3969/j.issn.1000-565X.2015.06.017
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    Aiming at the water landing of amphibious aircrafts，this paper presents a fluid-structure interaction (FSI) model of a certain amphibious aircraft head and analyzes the transient structural dynamic response of the head ditching by using the coupled Eulerian-Lagrange (CEL) method． Moreover，the stress，impact force and mass center velocity of the head at different ditching angles and vertical speeds are discussed． The results show that (1) the bottom pressure peak appears in the initial ditching stage and appears again with the heading up of the air-craft head; (2) during the ditching，the pressure of the head skeleton changes significantly; (3) with the de-crease of the hitting angle，the stress of the head reduces; and (4) both the head stress and the bottom impact force reduce with the decrease of ditching speed．
    Singular Perturbation Analysis of Large-Diameter and Thin-Wall Pipeline During Ultra-Deep S-lay Installation
    Han Qiang Wang Zhi-gang Zhang Yong-qiang Tao Xu
    2015, 43(6):  116-121.  doi:10.3969/j.issn.1000-565X.2015.06.018
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    In this paper，the analytical solution of the pipeline during ultra-deep S-lay installation was obtained based on the theory of singular perturbation． Then，the effects of tension，water depth and current force on the pipeline's configuration and bending moment were investigated． Moreover，a numerical simulation of the pipeline installation was conducted by means of the finite element method，and the results were compared with the theoreti-cal singular perturbation solution． Theoretical results show that (1) a suitable increase in tension is good for the installation because it makes the pipeline configuration more flat; (2) deep water may result in steep configuration and large moment peak near the seabed，which is harmful to the pipeline installation; and (3) the current force has the same effect on the pipeline installation when it is opposite to the forward direction．
    Molecular Dynamics Simulation of Wrinkles in Zigzag Graphene Under Gradient Tension
    Huang Jian-zhang Han Qiang
    2015, 43(6):  122-126,141.  doi:10.3969/j.issn.1000-565X.2015.06.019
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    This paper deals with molecular dynamics simulation of the wrinkling deformation of a zigzag square sin-gle-layer graphene sheet (SLGS) subjected to gradient tensions． In the investigation，the formation and evolution of the wrinkles on graphene surface are analyzed，and the effects of boundary and loading conditions on the wrink-ling deformation are explored． Then，the variations of the wrinkling amplitude，the wavelength，the out-of-plane displacement and the direction angle with the loading displacement are revealed，and the effects of graphene size，temperature and loading grad on the wrinkling are discussed． It is found that (1) the formation and evolution process of wrinkles can be divided into four stages，namely the prophase stage，the metaphase stage，the ana-phase stage and the telophase stage; (2) with the increase in loading displacement，the wrinkling amplitude，the ratio of amplitude to wavelength and the maximum out-of-plane displacement all increase，while the wrinkling wavelength and the direction angle decrease; and (3) both the size and the temperature remarkably affect the gra-phene wrinkling，while the loading grad has little effect on the wrinkling．
    In-Plane Free Vibration of Rectangular Plates in Arbitrary Boundary Conditions
    Wang Qing-shan Shi Dong-yan Luo Xiang-cheng
    2015, 43(6):  127-134.  doi:10.3969/j.issn.1000-565X.2015.06.020
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    This paper deals with the in-plane free vibration of rectangular plates in arbitrary boundary conditions via the improved Fourier series method (IFSM)． In the investigation，first，the admissible functions of the plate dis-placement are expressed as an improved Fourier sine series to overcome the relevant discontinuities or jumps of elas-tic boundary conditions． Then，the unknown expansion coefficients of the admissible functions are considered as generalized variables and are determined by using the Ｒayleigh-Ｒitz technique combining with the energy functional based on the energy theory． Thus，the common in-plane vibration problem is converted into a standard eigenvalue problem． Finally，the results of rectangular plates in various boundary conditions are presented and are compared with those in the literature and with those obtained by the finite element method． It is found that the proposed method is of strong reliability，good convergence and high accuracy．
    Biological Engineering
    Identification and Nitrite Degradation Ability of Bacillus cereus LJ01
    Liu Dong-mei Luo Tong-hui Yang Dan-xia Huang Juan Wu Hui Yu Yi-gang Li Li
    2015, 43(6):  135-141.  doi:10.3969/j.issn.1000-565X.2015.06.021
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    A strain LJ01 with strong nitrite degradation ability was isolated from fermented bean paste and was iden-tified as Bacillus cereus． Then，the primary cell localization of this nitrite reductase was examined by measuring the enzyme activity of different cellular components from LJ01 cell． After LJ01 was induced by 100 mg/L sodium nitrite solution and treated with lysozyme，the crude enzyme solution of LJ01 was first separated by means of the anion DEAE Sepharose Fast Flow chromatography，and the nitrite degradation activity of fractions a，b and c was measured． Moreover，by using inorganic electron donors such as 0. 1mol/L succinic acid and sodium sulfite solu-tion，fraction c was identified as a critical nitrite reductase and was separated by Sephadex G-150 column to get pure protein． The identification results show that 0. 54mg of active enzyme protein with an activity of 4004. 89U/mg can be obtained from 1L of the fermentation liquid，and that the specific NiR activity of the purified enzyme increa-ses by 17. 57 folds with a recovery of 2. 37%． In addition，SDS-PAGE results show that the monomer molecular mass of LJ01 is about 30ku．
    Analysis of Elimination Effect of Enzyme-Combined Mouthwash on Dental Plague
    Chen Gu Lei Hai-jin Wang Hong Chen Cong-cong Xiang Jia-jia Zhang Shao-bo
    2015, 43(6):  142-146.  doi:10.3969/j.issn.1000-565X.2015.06.022
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    Dental caries is closely related to dental plaque，a biofilm in which bacteria attach to the teeth surface．This paper deals with the feasibility of eliminating dental plague by using a kind of mouthwash in which combined enzymes are used to degrade glucan and starch． In the investigation，the Tureskey modified Q-H indexes of 20 vo-lunteers were measured to compare the elimination effect of the enzyme-combined mouthwash，the mouthwash with-out enzymes and the commercially available mouthwash with essential oil． Statistical results indicate that，when the enzyme content is higher than 0. 5mg/L，the mouthwash containing β-glucanase and α-amylase is more effec-tive than the one without enzymes; and that，when the enzyme content is higher than 5. 0mg/L，the enzyme-com-bined mouthwash presents a dental plague elimination rate higher than that of the commercially available mouth-wash． It is thus concluded that the mouthwash with combined enzymes is effective in eliminating dental plague．This research lays a theoretical foundation for developing products for the daily prevention of dental caries．
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