Table of Content

25 February 2015, Volume 43 Issue 2

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Food Science & Technology

Enzymatic Preparation，Separation，Purification and Antioxidant Activity Evaluation of Whey Protein Peptides

Ren Jiao-yan Lai Ting Jiang Yan-qing Lu Yun-jun Liu Peng Liao Wen-zhen

2015, 43(2):  1-7.  doi:10.3969/j.issn.1000-565X.2015.02.001

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Whey protein peptides were prepared via enzymolysis，and the corresponding conditions were optimized by taking antioxidant activity and protein recovery as two indicators． Then，the enzymatic hydrolysate was separated and purified by means of column chromatography，and the molecular mass of the product was measured． The results indicate that (1) alkaline protease is more suitable for the enzymolysis than trypsogen，flavorzyme and papain，with an optimal substrate dosage of 4． 0%，an optimal enzyme dosage of 8000U/g and an optimal enzymolysis time of 4h; (2) fraction A obtained by DEAE-52 cellulose column chromatography exhibits the highest antioxidant activi-ty，with a reducing power value of 0． 3200 ±0． 0041 and a DPPH radical scavenging activity of 6． 58% ±0． 36%;(3) further separation of fraction A via Sephadex G-15 gel column chromatography helps to obtain fraction G with a DPPH radical scavenging activity of 6． 73% ±0． 083%; and (4) the main component identified from fraction G，which contains three amino acids (namely Lys，Leu and Ser)，is of a molecular mass of 378u．


Determination of 4-Methylimidazole Content via Ion Chromatography-Mass Spectrometry

Yu Shu-juan Liu Ding-bo Xu Xian-bing Wu Xin-lan

2015, 43(2):  8-12.  doi:10.3969/j.issn.1000-565X.2015.02.002

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In order to quantitatively and qualitatively determine the content of 4-methylimidazole in samples with simplicity，convenience and accuracy，a new method using cation exchange chromatography-mass spectrometry was developed． This method，with a detection limit of 0． 25μg/L，a linear range varying from 2． 5 to 200μg/L，a linear correlation coefficient of 0． 9997，a relative standard deviation of 2． 32% ～ 4． 25% and a recovery varying from 92． 7% to 96． 3%，was then used to test the 4-methylimidazole in caramel pigment，cola and some other samples．The results show that the proposed method is of high separation degree，good sensitivity，accurate quantification，high precision and low detection limit．


Heat Penetration Characteristics and Quality Kinetics of Roasted Broiler Chicken Wings During Heat Sterilization

Li Bian-sheng Tan Li Zhou Hou-yuan Ruan Zheng Guo Wei-bo Lin Guang-ming Yang Huan-bin

2015, 43(2):  13-19.  doi:10.3969/j.issn.1000-565X.2015.02.003

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This paper deals with the heat penetration characteristics，quality change and quality kinetics of roasted broiler chicken wings with different moisture contents (w =30% ～40%) sterilized at different lethality values (F =0 ～5min)． The results indicate that (1) the heating and cooling rate indexes (f h and f c ) as well as the heating and cooling lag factors (j h and j c ) both decrease with the decrease of moisture content; (2) samples with lower moisture content may reach a higher lethality value at the same heating and holding time; (3) F value has no obvi-ous effect on the water activity a w (P ＞0． 05); (4) the curves of TBA value obey the zero-order kinetic equation and the corresponding reaction rate k increases with the decrease of moisture content; (5) sterilization with low le-thality value helps to improve the shear force，hardness and chewiness of roasted broiler chicken wings，and the corresponding decreasing curves all obey the first-order kinetic equation; and (6) the damage rates of shear force，hardness and chewiness all decrease with the decrease of moisture content．


Preparation of Frucooligosaccharides via Biotransformation by Aspergillus niger 6640

Liu Dong-mei Zhou Jin-song Shang Yong-he Yang Dan-xia Ke Yi-chun Yu Shu-juan

2015, 43(2):  20-26.  doi:10.3969/j.issn.1000-565X.2015.02.004

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In this paper，the preparation conditions of fructooligosaccharides (FOS) via the biotransformation by Aspergillus niger 6640 (A．niger 6640) were optimized，and the properties of crude enzyme of β-Ffase from A． ni-ger 6640 were investigated． Then，β-Ffase was isolated and purified by using an anion column of DEAE Sepharose CL-6B，and its molecular mass was preliminarily measured by means of SDS-PAGE electrophoresis． The results show that (1) the optimal conditions for FOS preparation should be controlled at a pH value of 7． 6，a fermentation time of 40 h，a fermentation temperature of 33 ℃ and a sucrose mass fraction of 40%; (2) in the buffer of Na 2 HPO 4 -citric acid for the biotransformation using vacuum-dried β-Ffase，the optimal conditions are determined as pH 6． 5，a reaction time of 16h and a β-Ffase dosage of 0． 19g; and (3) the molecular mass of β-Ffase after isola-tion and purification is about 75ku．


Effects of Heat-Moisture Treatment on Physicochemical Properties and Digestibility of Maize Starch

Fu Xiong Zhang Ming Zhu Si-ming Huang Qiang

2015, 43(2):  27-32,65.  doi:10.3969/j.issn.1000-565X.2015.02.005

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Heat-moisture treatment (HMT) was performed for normal maize starch with different moisture contents，and the effects of HMT on the morphology，viscosity，thermodynamic properties，crystallinity and digestibility of the starch were investigated． The results show that (1) the integrity of starch granules with HMT keeps well but frag-ment appears on the granules surface; (2) the polarization cross still exists in the treated starch but it partially dis-appears at high moisture content; (3) after the HMT，the gelatinization temperature of starch increases，the peak viscosity，the terminal viscosity，the breakdown value and the gelatinization enthalpy decrease，while the crystallin-ity first increases and then decreases with the increase of moisture content; (4) A + V crystal pattern appears in the starch treated at high moisture content，which indicates the formation of starch-lipid complex; and (5) the contents of resistant starch and slow digestible starch in the starch with HMT both increase with the increase of the moisture content．


Architecture & Civil Engineering

Test and Numerical Analysis of Subway-Induced Vibrations of Metro-Line Nearby Buildings

2015, 43(2):  33-40.  doi:10.3969/j.issn.1000-565X.2015.02.006

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The subway-induced vibration response of the nearby buildings along Guangzhou Metro Line 3 was inves-tigated via site measurement，and the vibration propagation in buildings was numerically analyzed． The results show that (1) in frame structures，the vibration peak decreases with the increase of building height; (2) the subway-in-duced vibration frequency varies from 30 to 80Hz，mainly in the range of 30 ～50Hz; (3) the vibration reduction of the internal structure column is more significant than that of surrounding columns; (4) more beams on the column may result in greater energy loss; and (5) the acceleration caused by subway vibration may have an impact on the comfort level of people in buildings．


Simplified Calculation of Longitudinal Seismic Ｒesponse of Cable-Stayed Bridges Subjected to Pulsed Ground Motions

Xu Yan Huang Yong-fu Li Jian-zhong

2015, 43(2):  41-47.  doi:10.3969/j.issn.1000-565X.2015.02.007

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In order to investigate the effect of near-fault pulsed ground motions on cable-stayed bridges，the charac-teristics of near-fault pulsed ground motions are analyzed and are fitted to different numerical pulse models by means of the least square method． Then，the complex cable-stayed bridge is simplified into a system with single degree of freedom in longitudinal direction via the equivalent modal method，and the dynamic differential equations of the ca-ble-stayed bridge subjected to near-fault pulsed ground motions are therefore established and solved． Meanwhile，the analytical relationships between the top displacement as well as the bottom moment of the tower and the period as well as the amplitude of the pulse velocity are obtained to further reveal the general law of bridge seismic respon-ses varying with pulse parameters． Finally，finite element analyses of both single-tower and double-tower cable-stayed bridges are carried out to verify the accuracy of the proposed method． The results indicate that the method is of simplicity，feasibility and an acceptable error．


Vertical Vibration of Partially-Embedded Pile in Unsaturated Soil

Zhang Min Wang Xing-hua Feng Guo-rui Liang Yan

2015, 43(2):  48-57.  doi:10.3969/j.issn.1000-565X.2015.02.008

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In this paper，first，the motion response of unsaturated free field under symmetrical condition is obtained via operator splitting and variable separation，in which the wave equation of three-phase porous media and the cou-pling of two immiscible fluids (namely water and air) filled in pores are taken into consideration． Then，on the ba-sis of the continuity condition of upper and lower regions as well as the assumption of Winkler's elastic support at the pile tip，the differential equation of pile vibration is deduced，the frequency domain response of the partially-embedded elastic support pile under steady harmonic vibration is theoretically analyzed，and the closed forms of the impedance function of pile top are obtained． Finally，the complex impedance curves of pile top in unsaturated soil are compared with those in saturated soil，and good agreement is found between the theoretical results and the re-sults obtained from the existing boundary element method and the virtual pile method，which means that the theoret-ical derivation is correct． Parameter analysis results indicate that the complex stiffness of pile top significantly de-creases with the increase of extended segment length; and that the pore water contributes to the dynamic behavior only in approximately saturated condition，while the influences of the saturation and the reaction coefficient at soil layer bottom are rather limited．


Fire Resistance of Bolted Steel-Glulam-Steel Connections

Zhang Jin Xu Qing-feng Bai Yi-wei Cai Jian-guo

2015, 43(2):  58-65.  doi:10.3969/j.issn.1000-565X.2015.02.009

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In order to reveal the fire resistance of bolted steel-glulam-steel connections using common tree species in China as the material，four connection specimens were tested to obtain the corresponding charring rates，and two groups of (eight) specimens were tested to reveal their fire endurance in different load levels． It is found that (1) the charring rate of interior area at steel splint edge is lower than that of external area; (2) the horizontal charring rate is lower than the vertical one in different cross sections; (3) the charring rate tends to reduce with the prolon-ging of fire duration; (4) changing the end-to-end distance from 7d to 10d cannot remarkably improve the fire en-durance limit of the bolted connections when the distance meets the regulatory requirements; (5) the fire endurance limit of the connections significantly decreases with the increase of load level; and (6) in the same conditions，the temperature rise of specimens in fire endurance tests is higher than that in charring rate tests．


Initial Parameter Method for Deflection Calculation of Concrete Composite Girder with Corrugated Steel Webs

Li Ming-hong Wan Shui Jiang Zheng-wen Ma Lei

2015, 43(2):  66-74.  doi:10.3969/j.issn.1000-565X.2015.02.010

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In order to accurately calculate the deflection of concrete composite girder with corrugated steel webs，the initial parameter equations of deflection curve of the girder，which take into consideration the influence of shear deformation，were deduced． In the investigation，first，the distribution characteristics of the shear stress in girder sections were analyzed，and a simplified formula for calculating the shear stress in webs was obtained． Then，the initial parameter equations of deflection curve of the girder were deduced，and a deflection calculation method was put forward． Moreover，the deflection of concrete composite girder with corrugated steel webs under three typical loads，namely the midspan-concentrated load，the symmetrical load and the uniformly-distributed load，was ana-lyzed by using the proposed method，and the results were compared with those obtained by experiments and finite element analysis，finding that the proposed theoretical method is accurate and applicable． Finally，by using the proposed method and the finite element method，the influences of depth-to-span ratio and aspect ratio on the shear deformation of the composite girder were explored，and a limit value of depth-to-span ratio was suggested for deter-mining whether the influence of shear deformation should be considered during the deflection calculation．


Distortional Buckling Analysis of Steel-Concrete Composite Box Beams Under Negative Moment

Zhou Wang-bao Jiang Li-zhong Li Shu-jin Kong Fan

2015, 43(2):  75-80,95.  doi:10.3969/j.issn.1000-565X.2015.02.011

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Distortional buckling is one of the important buckling patterns of steel-concrete composite box beams un-der negative moment，and the rotational and lateral restraint stiffness of the steel beam bottom plate is one of the key factors influencing the distortional buckling． In this paper，the equivalent lateral and rotational restraint stiff-ness of the steel beam bottom plate in negative moment region is investigated，and a coupling relationship between the restraint stiffness and the external load is revealed． Then，formulas to calculate the critical stress of the flexural-torsional buckling of steel-concrete composite box beams are deduced based on the elastic foundation beam method，and the corresponding critical buckling moments are further obtained． The proposed calculation method is finally compared with the existing methods through examples． Example results show that the distortional buckling moment of the composite box beams under negative moment is only slightly affected by the length; and that，under negative moment，the calculated buckling moments accord well with those obtained by ANSYS finite element method when the reduction factor of rotational restraint stiffness is set as 0． 5． The proposed method makes use of the lateral and rotational restraint stiffness of the steel beam bottom plate in a more scientific manner，and the coupling instability between the steel beam bottom plate and the web plate is considered，so that the method is of great significance in the sense of physics and of great convenience as well． This research provides a theoretical foundation for the calcu-lation of critical stress of distortional buckling of the composite box beams under variable axial force．


Effect of Green Technology on Eco Performance of Office Buildings in the South of the Five Ridges

Jiang Tao Hu Wen-bin Liang Tian

2015, 43(2):  81-87.  doi:10.3969/j.issn.1000-565X.2015.02.012

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Based on a national three-star greening project，namely the project of office hall design for the adminis-trative committee of Dongguan Eco Park，a series of computer simulations and energy consumption measurements are carried out to analyze and compare the effects of several passive and active energy-saving techniques on the eco performance of office buildings in the South of the Five Ｒidges． The passive energy-saving techniques include the o-rientation optimization as well as the utilization of sunshading，natural lighting and ventilation，and the active ener-gy-saving techniques include water recycling and air conditioning supported by water source heat pump． Then，a priority of the aforementioned passive techniques with less technological demand but greater efficiency，as well as an auxiliary use of the active energy-saving techniques to meet the requirements in particular conditions，is sugges-ted，which helps to improve the eco performance and reduce the energy consumption of office buildings．


Mechanical Engineering

Design of Extrusion Equipment with Axial Screw Vibration and Simulation of Vibration Characteristics

Wu Shang-sheng Hu An-tao Du Jin

2015, 43(2):  88-95.  doi:10.3969/j.issn.1000-565X.2015.02.013

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In this paper，first，novel mechanical principle-based extrusion equipment with axial screw vibration is designed，and the principle of the axial screw vibration is analyzed． Then，according to the theory of envelopes，the mathematical equations of the undulant vibration surface are established，and a 3D model of the extrusion e-quipment is constructed． Moreover，by the force analysis of the vibration parts，a physical model describing the screw vibration is established，and the key parameters are theoretically inferred out． Finally，in ADMAS environ-ment，a dynamic simulation of vibration characteristics of the extrusion equipment is carried out． The results show that the designed extrusion equipment exhibits a simple harmonic vibration waveform with small distortion and high stability，which means that the equipment is feasible and effective．


Theoretical Investigation into Friction Ｒesistance Calculation of Van Body Surface in the Presence of Air Film

Xie Xiao-peng Cao Li-feng Zeng Jian-hao

2015, 43(2):  96-101.  doi:10.3969/j.issn.1000-565X.2015.02.014

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According to the friction resistance decrease of van body surface observed by experiments in the presence of air film，three theories，namely the thickened boundary layer theory，the mixed deceleration theory and the thickened boundary layer-mixed deceleration theory，are put forward to explore the mechanism of air-film drag re-duction，and a model to calculate the friction resistance of van body surface in the presence of air film is estab-lished． Then，the friction resistances of van body surface with and without air film are qualitatively compared and analyzed，respectively． The results show that the friction resistance decreases in the presence of air film，which is consistent with the previous experimental results obtained by the authors． This research provides a theoretical foun-dation for the practical application of air-film drag reduction of van body surface．


Blade Analysisof Wind Turbine Considering Aeroelasticity

Chen Jin Li Song-lin Guo Xiao-feng Sun Zhen-ye

2015, 43(2):  102-106,113.  doi:10.3969/j.issn.1000-565X.2015.02.015

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A novel approach，which utilizes a modified blade element-momentum theory and the finite element method，is presented to analyze the blade performance of wind turbine considering aeroelasticity． Then，the ap-proach is used to analyze the performance of the blades of an 850MW wind turbine at various wind speeds． The re-sults show that aeroelasticity obviously influences the performance of large-size wind turbines at high wind speed and greatly reduces the accuracy of the original design． The presented approach is of guiding significance for the aerody-namic shape design，load calculation and structural design of blades．


Springback Prediction of Ｒectangular Profiles During Three-Dimension Stretch Bending Forming

Teng Fei Liang Ji-cai Zhang Wan-xi Wang Xue Gao Song

2015, 43(2):  107-113.  doi:10.3969/j.issn.1000-565X.2015.02.016

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In this paper，first，a reconfigurable flexible die for the three-dimension stretch bending forming is de-signed，and the springback of profiles during the forming is predicted by means of the support vector regression and the finite element simulation． Then，six factors that greatly affect the springback magnitude (including material pa-rameters，geometrical parameters and process parameters) are analyzed by using the finite element method，and their impact trends on the springback are also investigated． Moreover，these six factors are employed to design a simulation of three-dimension finite-element stretch bending，and the simulated results are used to train and test the springback prediction model based on the support vector regression machine． Finally，for the purpose of verifying the proposed apringback prediction model，the predicted results are compared with those obtained by the widely-used neural network forecasting method and the finite element simulation． It is found that the proposed model is more accurate than the neural network-based method，and that，in experiments，suitable compensations to the die shape according to the springback value predicted by the model may effectively reduce the springback and the shape deviation．


Vision Recognition and Framework Extraction of Loquat Branch-Pruning Robot

Huang Biao Shao Ming Song Lei

2015, 43(2):  114-119,126.  doi:10.3969/j.issn.1000-565X.2015.02.017

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Proposed in this paper is a method of image recognition and framework extraction for loquat branches，which is based on the analysis of the image characteristics of loquat branches． In this method，first，a common seg-mentation threshold is determined by transforming the brightness intensity． Then，the initial characteristic image of branches is obtained by the superposition of the segmented image and the converted binary image． Moreover，the linked feature of loquat branches is used to extract the image feature again and to eliminate the background noise．Finally，a compensation of the boundary contour and non-rational discontinuity of branches image is made to imple-ment the extraction of branches frame and to acquire the branche diameter and the center coordinates for robot prun-ing． A case study is also carried out to verify the accuracy of the proposed method，and an identification rate of 91．2% is obtained．


Optimal Design of Generalized Stewart Platform with Global Dynamic Isotropy Based on a Pair of Circular Hyperboloid of one Sheet

Tian Ti-xian Jiang Hong-zhou He Jing-feng Tong Zhi-zhong Huang Qi-tao

2015, 43(2):  120-126.  doi:10.3969/j.issn.1000-565X.2015.02.018

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The traditional Stewart platform cannot achieve complete dynamic isotropy due to its strict payload re-quirement，while the generalized Stewart platform based on a pair of circular hyperboloid of one sheet gives the ana-lytical form of parameters constraint conditions satisfying local complete dynamic isotropy，and breaks the limit of payload characteristics． In this paper，for the purpose of measuring the modal frequency characteristics of general-ized Stewart platform in large workspaces，a new global dynamic isotropy index is proposed based on the modal a-nalysis． By using this index as the optimal goal and by taking the analytical form of local complete dynamic isotropy as the constraint condition，a structural optimization method，which satisfies the local complete dynamic isotropy and the best global dynamic isotropy in workspace，is proposed． Design example shows that the proposed method provides a novel approach to designing Stewart parallel platform in large workspaces．


Materials Science & Technology

Flexural Load-Affected Diffusion rules of Chloride Through Concrete in Splash Zone

Xiong Jian-bo Su Da-gen Li Peng-ping Wang Sheng-nian

2015, 43(2):  127-132,138.  doi:10.3969/j.issn.1000-565X.2015.02.019

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The influence of stress level on the diffusion rules of chloride through maritime high-performance con-crete in splash zone was investigated under constant flexural load，and the load-affected microstructure of the con-crete and the hardened paste was also analyzed by means of SEM-EDS and BET tests． The results show that (1) in the pure bending section，the content of chloride in the concrete at a given depth increases with the increase of the flexural load; (2) for typical maritime high-performance concrete mix，there is approximately an exponential corre-lation between the flexural load and the constant load factor，so that the influence of flexural load on chloride diffu-sion coefficient should be considered in the durability design of concrete structures; (3) the increase in flexural load not only widens the micro-cracks in the interfacial transition zone but also improves the proportion of capillary and macro pores in the hardened paste，and eventually results in the increase of the total pore volume and average pore size，thus decreasing the resistance of concrete to chloride ion penetration．


Influence of Polyacrylamide on Interfacial Properties of Macro-Synthetic Fiber/Cement Matrix

He Rui Li Yong-peng Ren Si-run Wang Zhen-jun

2015, 43(2):  133-138.  doi:10.3969/j.issn.1000-565X.2015.02.020

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In order to overcome the poor bond performance of macro-synthetic polypropylene fiber/cement matrix，macro-synthetic polypropylene fiber was soaked in polyacrylamide solution，and fiber pullout test，microhardness test，X-ray diffraction analysis and scanning electron microscopy analysis were subsequently carried out to evaluate the effect of polyacrylamide on the interfacial properties of fiber/cement matrix． The results show that fiber/matrix interfacial bond properties improve due to the treatment with polyacrylamide solution; for instance，the fiber pullout curve becomes fuller and the interfacial debond postpones． Moreover，significant improvement can be observed with the increase of polyacrylamide content in the solution． It is also found from microanalysis that the treatment results in a decrease of CH crystal in the interfacial region，an increase of interface microhardness，a thinner transition lay-er as well as a densified hydration products structure with alternate CH，C-S-H and AFt． Thus，the weak area be-tween the fiber and the cement matrix improves significantly．


Properties of Asphalt Modified with Organic Montmorillonite/Epoxy Resin

Xiao Xin-yan Zhang Deng-ke Yan Ying Zhu Wen-qiang

2015, 43(2):  139-143,150.  doi:10.3969/j.issn.1000-565X.2015.02.021

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Organic montmorillonite (OMMT) /epoxy resin was used to modify asphalt via melt blending，and the compatibility of the compatibilizer and asphalt，as well as the microstructure，tensile strength，break elongation，thermal stability and viscosity-temperature properties of the modified asphalt，was characterized by means of FT-IＲ，XRD，fluorescent microscopy，universal material testing，TG analysis and Brookfield viscometry． The results show that (1) the dispersion of epoxy resin in the modified asphalt becomes more uniform due to the incorporation of OMMT，which results in an exfoliated structure; (2) the high-temperature performance and mechanical properties of the modified asphalt improve after the doping of OMMT; (3) as compared with the asphalt modified with epoxy resin，the asphalt modified with OMMT/epoxy resin exhibits better thermal stability，with increase of 30． 1℃ and 15℃ in initial and final decomposition temperature respctively; and (4) the asphalt modified with OMMT/epoxy resin is suitable for road construction due to its gently improved viscosity during the curing process．


Infiltrants for Post-Processing of Three-Dimension Printing Specimens

Cheng Jiang Wu Jiao-jiao Xu Shou-ping Zhou Dong-wei Zhou Liang

2015, 43(2):  144-150.  doi:10.3969/j.issn.1000-565X.2015.02.022

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This paper deals with the water resistance，compressive strength，dimensional deviation and surficial mi-crostructure of gypsum-based three-dimension printing specimens affected by filling enhancers(namely infiltrant A)，base materials of infiltrant B，dosage of waterborne epoxy emulsion in infiltrant B and immersion time． The re-sults show that(1) nano-silicone superhard curing agent is the most suitable enhancer for infiltrant A because it sig-nificantly improves the compressive strength of printing specimens; (2) waterborne polyurethane emulsion PU-202B is the most appropriate base material of infiltrant B; (3) the addition of waterborne epoxy emulsion in infiltrant B improves the compressive strength and water resistance of printing specimens，but excess waterborne epoxy emulsion may result in a dimensional deviation of the specimens; (4) the best immersion time for the three-dimension print-ing specimens into infiltrants A and B is 130s and 35s，respectively; and (5) after being immersed in infiltrant A and subsequently in infiltrant B，the specimens are of high compressive strength，weak water absorption，smooth surface and strong bond capability．