Table of Content

25 June 2017, Volume 45 Issue 6

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Physics

Statistical Properties of Partially Random Complex Network Based on Penrose Tiling

FU Xiu-jun PENG Cai-xia DUAN Xue-qing

2017, 45(6):  1-7.  doi:10.3969/j.issn.1000-565X.2017.06.001

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In order to extend the models and exploit new features for complex networks,the statistical properties of random complex networks are explored.In the investigation,first,on the basis of the Penrose tiling composed of two kinds of rhombus,random connections of the vertex are added to construct a partially random complex network in which the connecting probability depends on the vertex type.Then,the main characteristic parameters of the network are calculated by using analytical and numerical methods.It is found that the degree distribution,the ave- rage inter-node distance and the cluster coefficient of the partially random complex network are all close to those of general random networks but obey different variation laws,which means that the proposed quasi-periodic complex network possesses not only the common properties of general networks but also abundant specific features.

Dynamic Distribution of Electrostatic Potential in Vertical Cylindrical Oil Tank During Filling

WANG Liang-wang CHEN Guo-hua

2017, 45(6):  8-14.  doi:10.3969/j.issn.1000-565X.2017.06.002

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In this paper,first,by taking into consideration the variation of space charge density with the filling time in oil tanks in the filling process,a dynamic distribution model of electrostatic potential in vertical cylindrical oil tanks is established.Then,the effectiveness of the model is verified by comparing the results obtained by the model with the experimental ones in the literature.Finally,the proposed model is employed to analyze the dynamic distri- bution laws of electrostatic potential in three kinds of tanks respectively without filling pipeline,with middle crane tube filling and with bottom pipeline filling.The results show that (1) both the maximum spatial potential and the maximum oil-surface potential of the three above-mentioned tanks first increase and then decrease with the oil filling rate; (2) the bottom pipeline slightly affects the electrostatic potential distribution in tanks,while the middle crane tube significantly reduces the potential; and (3) with the diameter increase of the middle crane tube,the maximum spatial potential decreases at constant filling flux but increases at constant filling velocity.This research provides references for the selection of transportation conditions and parameters and helps to reduce the electrostatic risk du- ring the filling of oil into tanks.

Investigation into All-Optical Diode Based on Cascaded Nonlinear Microcavity

LI Chao WANG Min LIU Dao-liu HU Yong-lu WU Jun-fang

2017, 45(6):  15-19.  doi:10.3969/j.issn.1000-565X.2017.06.003

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All-optical diode is one of the key devices of future optical communication and photonic computer.In this paper,the nonreciprocal optical transmission characteristics of a new-type all-optical diode based on nonlinear photonic crystal (PC) are analyzed by means of finite difference time domain,and two ultrashort pulse lasers are used to pump the PC directly-coupled microcavity and the side-coupled microcavity,respectively,so that the non- linear optical bistable state of the two microcavities can be accurately adjusted and a high-performance optical di- ode,which is of a unidirectional transmission rate up to 90% and a forward-reverse transmission contrast ratio of more than 80,is realized in a broad operating bandwidth of more than 0. 44nm (dozens of times that in the litera- ture).

Thermodynamic Mechanism of Electrocaloric Effect of Dielectrics in Electrostatic Field

HAN Guang-ze XING Qian

2017, 45(6):  20-24,30.  doi:10.3969/j.issn.1000-565X.2017.06.004

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The promising solid-state refrigerator based on the electrocaloric effect plays an important role in the cooling of microelectronic devices.In this paper,a fundamental thermodynamic differential equation considering the polar energy was proposed,and the thermodynamic expressions of heat capacity,temperature,entropy and heat flux in electrostatic field were derived.Then,a verification of the expressions was conducted by using the experimental data of barium titanate,and a good accordance was found.It is concluded that the electrocaloric effect owes itself to the variation of electric dipole moment with temperature and becomes obvious with the increase of temperature sensi- tivity of permittivity.Thus,the research on giant electrocaloric effect in the future should focus on the drastic change region of permittivity with temperature.

Effect of Sound Reinforcement System on Chinese Speech Intelligibility in Primary School Classrooms

PENG Jian-xin WANG Dan

2017, 45(6):  25-30.  doi:10.3969/j.issn.1000-565X.2017.06.005

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Chinese speech intelligibility was evaluated in 3 primary school classrooms with different reverberation time under the conditions with or without sound reinforcement system for children of different ages.The results show that，for both Grade 3 and Grade 5 children,when the interfered noise level in classrooms is relatively high (60dBA),not only the Chinese speech intelligibility scores without the sound reinforcement system but also the scores with the sound reinforcement system at a sound pressure level of 70 dBA are significantly improved and are higher than the scores with the sound reinforcement system at a sound pressure level of 75dBA.However,these in- telligibility scores are not significantly different from those obtained under the condition that the teacher uses normal speech sound pressure level to teach in quieter environmental noise conditions.It is thus concluded that,in order to obtain a speech intelligibility score equaling that without sound reinforcement system,a higher signal-to-noise ratio is needed when the sound reinforcement system is used.

Traffic & Transportation Engineering

Optimization of Metro and Bus Network Considering Travel Behaviors

TIAN Sheng XU Kai MA Mei-na

2017, 45(6):  31-36.  doi:10.3969/j.issn.1000-565X.2017.06.006

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In order to effectively adjust the supporting bus lines after the opening of a new subway line,an optimi- zation of metro and bus network is made from the viewpoint of travel behavior.By introducing the prospect theory to describe the behaviors of bounded rational travelers and by assuming that travelers always chase the maximum value of foreground,a model for route selection is set up.Moreover,the equilibrium state of the road network under the prospect theory and the utility theory is analyzed by testing the network.The results show that the time of equilibrium state under the prospect theory is longer than that under the utility theory,and that the former shows obvious flow oscillation.In addition,the influence of the change threshold of foreground value on the equilibrium flow reflects the risk resistance of travelers to uncertainty,so that it is more suitable for the real situation and more effective in determining the final bus line.

Condition Evaluation of Subgrade in Highway Operation Period Based on Analytical Hierarchy Process

WANG Yi-min GUO Ji-xing LI Lin-sheng HUANG Sheng-jun WANG Peng

2017, 45(6):  37-43,51.  doi:10.3969/j.issn.1000-565X.2017.06.007

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In order to further improve the maintenance quality of subgrade,the subgrade condition evaluation is analyzed based on the standard method and the analytical hierarchy process,respectively.Then,according to the investigation results of subgrade condition carried out for three typical highways in Guangdong Province,the weight parameters of twenty-one factors and five components are determined via an analytical hierarchy process,and the subgrade condition index of fifteen test sections is calculated.Finally,a comparison is made between the calcula- ted results and the results obtained by the standard method.It is found that,as compared with the standard me- thod,although the analytical hierarchy process basically gives the same results,it is more objective and can reflect the subgrade condition and diseases in highway operation period in detail,which helps to perform subgrade main- tenance engineering more reasonably with clear aims.

Offset Optimization Model Between Intersections with Different Signal Cycles

YAN Xiao-wen XU Jian-min JING Bin-bin

2017, 45(6):  44-51.  doi:10.3969/j.issn.1000-565X.2017.06.008

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In order to implement the coordination control between sub-regions with different signal cycles,the idea of coordination control between intersections with different signal cycles in a large period is proposed.Then,by ana- lyzing the traffic arrival law between intersections with different signal cycles,a delay model based on the traffic wave theory is established,and an offset optimization method based on the minimum delay is proposed.Finally,by taking two signalized intersections with different cycle lengths as the examples,a VISSIM simulation is performed to analyze the effect of coordination control in a comparative way.Simulated results show that,after the coordination control,the average vehicle delay and the average number of stops decrease by 13. 60% and 6. 43%,respectively,which means that the proposed method is effective.This research provides a novel idea as well as a method for the coordination control between sub-regions with different signal cycles.

Traffic State Identification for Urban Expressway Based on Spectral Clustering and RS-KNN

SHANG Qiang LIN Ci-yun YANG Zhao-sheng BING Qi-chun TIAN Xiu-juan WANG Shu-xing

2017, 45(6):  52-58.  doi:10.3969/j.issn.1000-565X.2017.06.009

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In order to improve the accuracy of traffic state identification for urban expressway,a traffic state identi- fication model based on spectral clustering and RS-KNN (Random Subspace Ensemble K-Nearest Neighbors) is de- veloped.In the investigation,first,on the basis of spot traffic parameters data and according to the operation cha- racteristics of traffic flow,the traffic state is divided into four categories with the consideration of the four levels of service for Chinese roads.Then,the classified traffic flow data are used to train the RS-KNN model.Finally,by using the real data of an expressway in Shanghai,China,an experimental verification and a comparative analysis for the proposed model are carried out.Experimental results demonstrate that the proposed model not only improves the accuracy of traffic state identification but also possesses good robustness; and that the identification rate of the proposed model is 7. 3%,4. 9% and 4. 5% higher than that of the standard KNN model,the BP neural network and the SVM model,respectively.

Experimental Investigation into Longitudinal Temperature Field of CRTS Ⅰ Ballastless Track in Bridge-Tunnel Transition Section

2017, 45(6):  59-65.  doi:10.3969/j.issn.1000-565X.2017.06.010

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According to the continuous observation of longitudinal temperature distribution of ballastless tracks and roadbed slabs in the high-speed railway bridge-tunnel transition section in China's central complex mountainous area,the corresponding temperature distribution laws were obtained,and a suitable spring longitudinal temperature gradi- ent load model was established.Analytical results show that (1) from the outside to the inside of the tunnel,the temperature variation amplitude of the rail gradually decreases,and the temperature peak time of 75 meters inside the tunnel lag for 4h than that of 22 meters outside the tunnel; (2) the longitudinal temperature of the rail increa- ses with the increase of the tunnel's diameter and the maximum position range locates at 0 ～8m; when the tunnel depth is more than 75m,the temperature variation amplitude of the rail obviously becomes small and remains stable at 0.2℃; (3) the longitudinal temperature of the roadbed slab increases with the increase of the tunnel's diameter and the maximum position range locates at 0 ～8m; when the tunnel depth is more than 25m,the temperature vari- ation amplitude of the slab obviously becomes small and remains stable at 1.7℃; (4) the maximum longitudinal temperature variation amplitudes of both the rail and the slab in a day appear in the duration of 14:00 ～ 16:00; and (5) the longitudinal temperature gradient mode can be divided into two types: one is the rail type and the other the slab type,and the longitudinal temperature gradients of both the rail and the slab can be fitted by the piecewise function.

Big Data-Based Fatigue Life Analysis of Steel Box Girder in Large-Span Suspension Bridge

MA Ru-jin XU Shi-qiao WANG Da-lei CHEN Ai-rong

2017, 45(6):  66-73.  doi:10.3969/j.issn.1000-565X.2017.06.011

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In order to effectively use the mass data accumulated by bridge monitoring system to analyze the perform- ance of a bridge,first,by taking Xihoumen Bridge as an object,a multi-scale nonlinear finite element model is established,and a method to verify the reliability of the proposed model according to such monitoring data as wind speed,temperature,vehicle load and displacement is presented.Next,on the basis of mass data recorded by the WIM system,six types of standard fatigue vehicles are determined and applied to the multi-scale finite element model to calculate the stress response of the details of steel box girder.Then,by combining Palmgren-Miner linear cumulative damage theory with the stress amplitude,the theoretical fatigue life of structural details in the steel box girder is obtained.Moreover,by means of filtering,denoising and other big data processing methods,the moni- tored stress data are analyzed to calculate the actual fatigue life of the weld details and to determine the correction coefficient of the theoretical fatigue life.Finally,according to the corrected fatigue life,the structural details of the steel box girder in different positions are divided into four fatigue grades.This research provides a new ap- proach to obtaining the fatigue life of the details without laying sensors.It also serves as a guidance for the daily maintenance and management of steel box girders in long-span bridges.

Pedestrian Detection Method Based on Adaptive Pulse-Coupled Neural Networks

WANG Ze-sheng DONG Bao-tian WANG Ai-li

2017, 45(6):  74-80.  doi:10.3969/j.issn.1000-565X.2017.06.012

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It is rather difficult to detect pedestrians accurately in the traffic images stained by speckle noise and in- tensity distortions under complex illumination.In order to solve this problem and improve the accuracy and automa- tion level of information extraction from traffic images,a new pedestrian detection method,which is based on adap- tive pulse-coupled neural networks,is proposed.In the investigation,first,the ignition contribution values between the central nerve and its neighborhoods are determined according to the quasi-Euclidean distance between pixels.Then,a key control parameter named initial threshold is set by merging gray feature and neighborhood information.Finally,multi-strategy morphological modifications are performed on the initial detection results to obtain the final pedestrian information.Experimental results demonstrate that the proposed method greatly eliminates the impact of noise,well restrains the over-segmentation,and helps to obtain satisfactory detection results with good adaptability.

Evolution Rule of Microcosmic Cracks in Pavement Concrete Under Multi-Field Coupling

QIN Xiao SHEN Ai-qin GUO Yin-chuan ZHOU Sheng-bo HE Tian-qin

2017, 45(6):  81-88,102.  doi:10.3969/j.issn.1000-565X.2017.06.013

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The evolution and spatial distribution rule of microcosmic cracks are two key factors affecting the durabi- lity of pavement concrete.In order to explore the evolution of microcracks initiation,propagation and compression for pavement concrete in actual working environment in cold regions,multi-field fatigue tests were conducted,and SEM,CT and image segmentation techniques were adopted to compare the crack characteristics such as area densi- ty,average width，maximum length and fractal dimension for specimens respectively in a single field,in double fields and in three-field coupling condition.Then,the dynamic damage rules of microcracks under different loading levels and with different coupling schemes were discussed in meso scale.The results show that (1) under the ac- tion of single load,the maximum length of cracks shows a“initiating-closing-extending”trend,while the average width reveals a“compressing-expanding”trend,and the fractal dimension first increases and then decreases with the increase of loading cycles; (2) the crystallization swelling stress initiated by loading-freezing-thawing coupling effect makes the crack area density and the maximum crack length both increase,and the concrete reveals fatigue failure with small crack length and width under 80% loading condition; (3) under the loading-freezing-thawing- wetting-drying three-field coupling condition,the additional dry shrinkage stress causes a shrinkage stress in the parallel direction of the crack and a compressive stress in the vertical direction of the crack,which makes the crack length increase,the crack width decrease,and more micro-cracks nucleate.

Chemistry & Chemical Engineering

Synthesis of Phenol-Furfural Resins Using Hydrogenolysis Products of Lignin Regenerated via Ionic Liquid Pretreatment

CHANG Jie KASSANOV Bekbolat WANG Ju LIU Jun FU Yan

2017, 45(6):  89-95.  doi:10.3969/j.issn.1000-565X.2017.06.014

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A hydrogenolysis process was performed for regenerated bamboo lignin after ［AMIM］OAc pretreatment by using a high-pressure batch autoclave with a rotation rate of 450r/min in 2MPa H 2 atmosphere at 260℃ for 80min,and a GC-MS analysis was conducted,finding that most hydrogenolysis products of lignin (HPL) are phenolic com- pounds with short chains or aromatic compounds containing phenol hydroxyl.Then,HPL was used as a substitution for phenol to synthesize phenol-furfural resins (PFU),and the effects of substitution rate of HPL for phenol on the bond strength,solid content,curing time,free formaldehyde content,free phenol content and viscosity of PFU were investigated.The results show that，at a substitution rate of 60%,the lignin-based PFU is of a bond strength up to 2. 06MPa as well as a free phenol content lower than those regulated by Chinese national standards,and the curing time greatly shortens.Moreover,DSC results indicate that the lignin-based PFU possesses strong thermosta- bility.

Preparation and Pb²⁺ Removal Capacity of Phosphorylated Lignin

PANG Yu-xia CAI Meng LOU Hong-ming

2017, 45(6):  96-102.  doi:10.3969/j.issn.1000-565X.2017.06.015

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Due to its limited adsorption capacity for metal ions in aqueous solutions,alkali lignin is unsuitable for direct industry application as an absorbent of heavy metals.In this paper,a phosphorylation modification of alkali lignin was carried out,and the adsorption capacity of the phosphorylated alkali lignin (PAL) for Pb²⁺ was investi- gated by means of IR,particle charge detection,SEM and atomic absorption spectroscopy,followed with a mecha- nism exploration.The results indicate that (1) after the phosphorylation,the surface of lignin becomes coarse and porous,the specific surface area increases from 2. 12 to 11. 17m² /g,and the adsorption process becomes fast,with a higher adsorption capacity of Pb²⁺ ; (2) the adsorption mainly depends on the electrostatic interaction between Pb²⁺ and such negative functional groups as phosphate,phenolic hydroxyl and carboxyl,as well as on the ion ex- change between H⁺ and Pb²⁺ ; (3) the Pb²⁺ removal capacity of PAL is mainly affected by the PAL mass,the ini- tial mass concentration of Pb²⁺ ,the pH value and the temperature; and (4) the Pb²⁺ removal increases with the increase of PAL mass and pH value,and reaches the maximum 92. 36% at 30℃.

Supercritical CO₂ Fluid Extraction of Natural Flavor Components in Tobacco Stem

YI Cong-hua JI Wei-ni KONG Hao-hui ZHOU Rong

2017, 45(6):  103-108,116.  doi:10.3969/j.issn.1000-565X.2017.06.016

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In order to implement the high-valued utilization of tobacco stem,supercritical CO₂ fluid extraction was conducted to extract the flavor components from waste tobacco stem and to prepare essential oil with natural tobacco flavors.Then,by taking the extraction yield as an evaluation index,single-factor and orthogonal experiments were respectively carried out to optimize the extraction process,Finally,the flavor components in the obtained extracts were analyzed by means of GC-MS.The results show that,under the optimal extraction conditions,that is,an ex- traction temperature of 60 ℃,an extraction pressure of 32 MPa,a CO₂ flow rate of 24 L/h,an extraction time of 2. 5 h,when 85% ethanol solution with a mass fraction in tobacco stem of 20% is adopted as the entrainer,the ex- traction yield reaches 1. 70%; and that many important flavor components are contained in the 27 kinds of identi- fied components,such as β-damascenone,megastigmatrienone,β-cembrenediol,geranyl acetone,neophytadiene,and so on.

Structure Characterization and Reaction Kinetics of TDI-TMP Prepolymer

ZHONG Li ZHANG Li HUANG Hong

2017, 45(6):  109-116.  doi:10.3969/j.issn.1000-565X.2017.06.017

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FT-IR,NMRand high-resolution MS were used to characterize the chemical structure of toluene diiso- cyanate (TDI)-trimethylolpropane (TMP) prepolymer,and HPLC-MS was adopted to detect the concentration of each oligomer in the reaction intermediates and to further reveal the reaction kinetics of TDI and TMP.The results indicate that (1) the TDI-TMP addition reaction is a second-order reaction; (2) temperature significantly affects the reaction selectivity of 2'-and 4'-NCO in TDI; (3) the 2'-NCO selectivity increases from 0. 41 to 0. 64 when the temperature increases from 50℃ to 80℃; (4) the reaction rate constants of the three steps of the reaction at 80℃ are 0. 18540,0. 03789 and 0. 01140mol^-1 ·L^-1 ·min^-1 ,respectively,with the corresponding activation energy be- ing 12. 76,16. 58 and 25. 63 kJ/mol,respectively; and (5) the third step of the reaction is more sensitive to temperature than the first two steps,so that appropriately raising temperature in the later reaction may result in a more sufficient reaction.

Catalytic Wet Peroxide Oxidation of Phenol on CeO₂ -ZSM-5 Fixed Bed Reactor

YANG Yi ZHANG Hui-ping YAN Ying

2017, 45(6):  117-123,130.  doi:10.3969/j.issn.1000-565X.2017.06.018

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In this paper,first,CeO₂ -ZSM-5 zeolite catalysts were prepared by means of impregnation method and were applied to the catalytic wet peroxide oxidation of phenol in a fixed bed reactor.Then,the phase structure,specific surface area and pore structure of CeO₂ -ZSM-5 were characterized via XRD and N₂adsorption-desorption.Finally,the effects of temperature,bed height and feed flow rate on the conversion rates of phenol,H₂O₂ and total organic carbon (TOC),as well as on the cerium leaching concentration and the selectivity of CO₂ ,were investiga- ted.Characterization results show that CeO₂ -ZSM-5 catalysts are micro-pore materials; and that，after the loading of active components,the crystal form of CeO₂ -ZSM-5 almost keeps unchanged but the specific surface area decrea- ses.Moreover,from the activity evaluation results,it is found that (1) the conversion rates of phenol,H₂O₂ and TOC,as well as the selectivity of CO₂ all increase with the increase of temperature and with the decrease of feed flow rate; (2) with the increase of bed height,the conversion rates of phenol,H₂O₂ and TOC all increase,while the selectivity of CO₂ decreases; (3) the cerium leaching concentration is small under all conditions,which means that the catalysts possess good stability; and (4) no by-products are observed in the process of CWPO.

Electrochemical Corrosion Behaviors of Titanium Alloy in Different Solutions

HE Ya-feng LU Wen-zhuang GAN Wei-min

2017, 45(6):  124-130.  doi:10.3969/j.issn.1000-565X.2017.06.019

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In this paper,first,the electrochemical corrosion behaviors of titanium alloy Ti6Al4V were investigated in such different solutions as NaCl,NaBr and KBr at various mass fractions (6. 5%,12. 5% and 18. 5%),and the corresponding corrosion polarization curves and dynamic parameters were obtained.Then,the electrochemical corrosion mechanism of titanium alloy was explored by means of SEM.Finally，the fractal feature of corrosion pits was obtained by means of the pixel-covering fractal dimension method,and the relationship between the corrosion sur- face topography and the fractal was revealed.The results show that (1) different from the titanium alloy in NaBr and KBr solutions,the titanium alloy in NaCl solution possesses wider activation range and longer oxidation dissolution time; (2) the corrosivity of titanium alloy in NaBr solution is stronger than that in NaCl and KBr solutions at the same mass fraction; and (3) the fractal dimension of titanium alloy in the three kinds of solutions gra-dually changes with the increase of mass fraction; for instance,the fractal dimension in NaBr solution is the most，which results in the most complex topography,while that in NaCl solution is the least,which results in a relatively flat topography.

Environmental Science & Technology

Investigation into Coagulation of Fine Particles by Combination of Seed Particles with Acoustic Wave

LIU Ding-ping LUO Wei-le

2017, 45(6):  131-138.  doi:10.3969/j.issn.1000-565X.2017.06.020

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In order to reveal the coagulation efficiency of fine particles by the combination of seed particles with acoustic wave,a numerical simulation is performed by coupling the population balance model and the Eulerian mul- tiphase model and by introducing the acoustic coagulation kernel function via some user-defined functions.From the simulation at constant particle size and flow velocity,the coagulation efficiency varying with acoustic frequency,sound pressure level,residence time and initial dust concentration is investigated.The results indicate that (1) the total coagulation efficiency of fine particles is greatly influenced by the acoustic frequency; (2) there is an optimum acoustic frequency for coagulation; (3) high acoustic frequency is conducive to the coagulation of small particles,while low acoustic frequency is favorable for the coagulation of large particles; (4) higher sound pressure level may result in greater vibration amplitude and higher coagulation efficiency of fine particles; (5) longer residence time benefits the collision between fine particles and thus promotes the coagulation; and (6) the increase of the initial dust concentration effectively improves the total coagulation efficiency of fine particles,and the maximum coagula- tion efficiency is near the initial peak diameter.All these above-mentioned conclusions are consistent with the ex- perimental ones.

Experimental Investigation into Removal of Soluble Silicate in Groundwater by Using Compound Coagulants

TAO Hui LAI Lian-hua CHEN Qing BAI Xin-zheng

2017, 45(6):  139-144.  doi:10.3969/j.issn.1000-565X.2017.06.021

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In order to effectively remove the soluble silicate in water,by taking the groundwater with a soluble sili- cate content of 50 ～60mg/L as the research objective,coagulation experiments for the soluble silicate removal by using different compound coagulants were performed.The results show that (1) when the dosage of Ca(OH)₂ is 450mg/L,the removal of soluble silicate and the turbidity reaches 51.16% and 74. 8%,respectively; (2) with the increase of Ca(OH)₂ dosage (more than 450mg/L),the removal of soluble silicate slightly increases while the pH value of the effluent greatly increases,too; (3) FeCl₃ has a poor removal on soluble silicate (less than 12. 55%) but has an advantage in turbidity control; (4) MgO possesses poor efficiency for both soluble silicate re- moval (less than 14. 53%) and turbidity control,and the optimal MgO dosage is 400mg/L; (5) the compound of FeCl₃ and Ca(OH)₂ possesses good performance on both soluble silicate removal and turbidity control,more than 60% of soluble silicate is removed and the effluent turbidity is less than 0. 65NTU; (6) the compound of FeCl₃ and MgO also possesses good performance on both soluble silicate removal and turbidity control,more than 75% of solu- ble silicate is removed; (7) the compound of Ca(OH)₂ and MgO results in a soluble silicate removal up to 73. 76%,which is relatively less than that contributed by Ca(OH)₂ only (81. 41%); and (8) among the three a- bove-mentioned compound approaches,the compound of FeCl₃ and MgO with a Fe³⁺ dosage of 16. 8 mg/L and a MgO dosage of 500mg/L is the best because it results in a soluble silicate removal of 76. 67% and an effluent tur- bidity of 0. 83NTU,and because it helps to obtain effluent with the lowest pH value,which saves the acid added in the later process.