Table of Content

25 September 2021, Volume 49 Issue 9

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Contents



2021, 49(9):  0. 

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Food Science & Technology

Investigation into Interaction Mechanism and Antioxidant Activity of Resveratrol and Modified Pectin



Li Lin, Yu An-ling, Wu Zhi, et al

2021, 49(9):  1-10.  doi:10.12141/j.issn.1000-565X.210046

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Resveratrol (RES) is a kind of stilbene compound with bioactivities, and its structure would be destroyed under ultraviolet or heating treatment, thus weakening its bioactivities. Pectin was able to form non-covalent bonds with RES, which was in favor of protecting antioxidant activity of RES. In this study, the structure of pectin was modified by the method of enzymolysis combined with ultrasound treatment. The molecular and microscopic structure of modified pectin was first characterized, and then the interaction mechanism between pectin and RES was discussed by isothermal titration method. At last, the antioxidant activity of RES-pectin complex under ultraviolet or heating treatment was tested. The resulted showed enzymolysis combined with ultrasound modification method remarkably reduced molecular weight and degree of methyl esterification (DM) of pectin. The molecular weight of 4 -min enzymolysis pectin (PE45U) was only 2% of that of unmodified pectin. SEM images showed more irregular fragments of pectin structure after modification. The combined enzymolysis with ultrasound method exposed a great number of –OH of pectin, which considerably increased the interaction sites and affinity between RES and pectin. The interaction sites number between PE45U and RES was 24 times of that between unmodified pectin and RES. The antioxidant activity of RES was significantly enhanced after interacting with pectin under ultraviolet or heating treatment (p<0.05). This study provided new insights to solve the problem of poor ultraviolet and thermal stability of RES and other stilbene when applied in food industry.

Safety and Potential Functional Characteristics of Bacillus coagulans 13002



LIU Dongmei, ZHAO Shan, ZHOU Qinyu, et al

2021, 49(9):  11-21.  doi:10.12141/j.issn.1000-565X.200367

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In this study，the acute toxicological safety，prebiotic in vitro and functional characteristics in vivo of Bacillus coagulans 13002 were evaluated.The results show that Bacillus coagulans 13002 is non-toxic，which acutely oral for female and male KM mice，and that it possesses good tolerance to simulated gastrointestinal digestion fluid.Moreover，it is resistant to Staphylococcus aureus ATCC 12598 （G+） and Escherichia coli ATCC 25922 （G-），which can obviously destroy the microstructure.These results indicate that the combination of Bacillus coagulans 13002 with fructooligosaccharide has a certain recovery effect on cyclophosphamide-induced tissue damage in mice，which can increase blood cells，improve protein synthesis rate and glucose utilization，and remove excess cholesterol to maintain the health of mice.

Recombinant Expression and Biochemical Characterization of Unspecific Peroxygenase GmaUPO



LAN Dongming NIE Xiaoshuang MA Yunjian WANG Yonghua

2021, 49(9):  22-28.  doi:10.12141/j.issn.1000-565X.210050

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Unspecific peroxygenase （UPO） has broad application prospects due to its unique stereoselectivity and enantioselectivity in catalyzing organic substrate.In this study，a putative unspecific peroxygenase gene （GmaUPO） was found from the genome of Galerina marginata，and the corresponding gene sequence was obtained by means of the whole gene synthesis technology.Moreover，Pichia pastoris X-33 gene engineering bacteria of GmaUPO inducible expression was constructed.Under the optimal fermentation condition，the enzyme activity of the fermentation broth can reach 6U/L，the relative molecular mass of GmaUPO is about 40ku，the optimal reaction temperature is 35℃and the optimal pH is 9.0.The recombinant GmaUPO can synthesize aromatic oxygen-containing compounds by using H2O2 to catalyze the hydroxylation of the inert C—H bond in aromatic substances under mild condition，which means that it possesses great application potential in the fields of flavors and fragrances.

Effect of DBD Cold Plasma Treatment on Activity and Conformation of Polyphenol Oxidase



CHENG Junhu WANG Huifen HAN Yongxu

2021, 49(9):  29-36.  doi:10.12141/j.issn.1000-565X.200635

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PPO （Polyphenol Oxidase）-induced enzymatic browning affects the quality of fruits and vegetables.To elucidate the mechanism of cold plasma on PPO and avoid browning，this study investigated the effect of cold plasma on PPO activity and conformation.The results showed that the enzyme activity of PPO could hardly be detected when the treatment time reached 120s and 180s.The active species of cold plasma destroyed the PPO secondary structures with the decrease of α-helix （from 39.92% to 9.47%），and the increase of β-sheet （from 15.32% to 44.30%） （180s）.Fluorescence emission spectrum showed that after cold plasma treatment，the PPO fluorescence intensity decreased from 512.9 to 330.6，and the position of the maximum absorption peak showed a red shift of 1.75nm.The 3D fluorescence spectra showed that the DBD plasma destroyed the polypeptide chain skeleton of the PPO molecule.Atomic force microscopy （AFM） showed that DBD plasma induced PPO molecule aggregation and then depolymerization，thus affecting the enzyme activity.In conclusion，cold plasma treatment changed the secondary and tertiary structures of PPO，and promoted the degeneration of protein oxidation and reduction of enzyme activity，providing theoretical support for the application of cold plasma in the inhibition of enzymatic browning and the maintenance of quality for fruits and vegetables.

Chemistry & Chemical Engineering

Structure and Properties of Eu3+-Containing PVA/CMC Fluorescent Hydrogels



YE Jun YE Fang XIONG Jian

2021, 49(9):  37-45.  doi:10.12141/j.issn.1000-565X.200726

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As a permanent implantable medical material and pharmaceutical formulation component，Polyvinyl alcohol （PVA） has a wide range of applications.In this work，water was used as the only medium to successfully prepare a composite fluorescent hydrogel of PVA，carboxymethyl cellulose （CMC） and carboxymethyl cellulose/rare earth complex （CMC/Eu，i.e.CE） by a freeze-thaw cycle method.The morphology and structure of the hydrogels were characterized by SEM and FT-IR.The results show that hydrogen bonding and other interactions occurred among CE，CMC and PVA to form multi-pore structure.DSC and XRD results show that the crystal structure of PVA is retained in the hydrogel after the addition of CMC，but the crystallinity decreases.The improvement of the mechanical properties of these hydrogels is due to the hydrogen bonding of the hydroxyl in CE，CMC and PVA molecules as well as other interactions between molecular chains，which improve the fusion between molecular chains and enhance the bonding strength among various components.Especially，when the mass ratio of CMC to PVA is 1：5，its tensile modulus of elasticity can reach 39.86kPa，and the compressive modulus of elasticity can reach to 273.31kPa.Photoluminescence （PL） results show that the PVA/CMC/CE hydrogel has the 5D0→7F2 characteristic emission peak of Eu3+ near 635nm when the excitation wavelength is 394nm.It displays red fluorescence under ultraviolet light，indicating that the hydrogel has a basis for potential applications in fluorescent probes，anti-counterfeiting and biomarkers.

Simulation and Experiment Investigation into Specific Heat Capacity Enhancement of Nitrate Molten Salt Nanofluid



WEI Xiaolan, LIN Guoqing, DING Jing, et al

2021, 49(9):  46-55.  doi:10.12141/j.issn.1000-565X.200641

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Nanofluid composed of molten salt and nanoparticles are important materials for the effective power ge-neration and heat storage system of solar energy.It is of great significance to find out why nanoparticles are able to enhance the specific heat capacity of molten salt.In this paper，nanoparticles were added in molten salt at diffe-rent contents，and the specific heat capacity variation of complex fluids was measured by means of DSC.Then，the molecular dynamic simulation was adopted to explore the reason for the rise of specific heat capacity of complex fluids.In the simulation，the number of molten salt molecules is fixed and the content of nanoparticles is changeable，so as to analyze the effects of the content of nanoparticles on the specific heat capacity，structure and distribution of molten salt.It is indicated that，when the mass fraction of nanoparticles is 1.0%~1.5%，the increase of specific heat capacity is the largest.The additional interaction force produced by the high-density clustering of molten salt anions on the surface of nanoparticles or by the regular restricted distribution on the surface of nanoparticles with smaller particle size （about 1nm） is the main reason for the increase of the specific heat capacity of nano-fluids.In addition，calculation results confirm the positive correlation between the dispersity of the nanoparticles and the increase of specific heat capacity.The addition of nanoparticles can reduce the distance between anion and cation in molten salt to a certain extent，resulting in the change of Coulomb energy，which is another reason for the increase of specific heat capacity.

Inversion Method Based on Chicken Swarm Optimization for Hazardous Chemicals Leakage and Diffusion Accident



CHEN Guohua, HU Xuewei, ZHOU Lixing, et al

2021, 49(9):  56-64.  doi:10.12141/j.issn.1000-565X.200695

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Dangerous chemicals leakage and diffusion accidents occur occasionally in the chemical plant.The key to dealing with such accidents is to confirm the location and rate of leakage sources quickly and accurately.Aiming at the defects of traditional leakage source inversion method，which is time-consuming and low accuracy，this paper proposes a leakage diffusion accident inversion method based on chicken swarm optimization （CSO） algorithm.This method takes the error between the gas concentration data monitored by the gas sensor and the calculated value of the model as the optimization objective.It transforms the inversion problem of hazardous chemical leakage and diffusion accident into an optimization objective minimization problem，and solves this problem with the chicken swarm optimization algorithm.In order to improve the accuracy of the algorithm，a weighted centroid method is used to construct a high quality initial solution set，which achieves an accuracy of 1m.The simulation results show that the chicken swarm optimization algorithm can accurately find the leakage source location in a short time，and its robustness can meet the actual demand; and that the method can realize the rapid and accurate positioning of hazardous chemical leakage sources in the chemical park and the accurate estimation of the strong leakage sources，thus providing timely and effective support for emergency decision-making.

Preparation of Butanone and Acetone via CatalyticDecarboxylation of Levulinic Acid



ZHANG Xin, SI Zhihao, SUN Yong, et al

2021, 49(9):  65-72.  doi:10.12141/j.issn.1000-565X.200022

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CuO-Bi2O3/H-β catalyst with high dispersion was prepared by taking H-β molecular sieve as the carrier，and butanone （MEK） and acetone （Ace） were prepared via the decarboxylation of levulinic acid （LA）.Then，the parameters affecting the decarboxylation performance of LA were investigated and the catalysts were characterized．Under the condition of 290℃，initial pH 5~6 and decarboxylation reaction for 3h，the conversion rate of LA can reach 88.06%，the yield of MEK can reach 40.75%，and the total yield of MEK and Ace can reach 61.05%.The research results show that the catalyst has high decarboxylation activity and excellent recycling performance.Moreover，the characterization results show that CuO-Bi2O3/H-β possesses both weak acid-base sites and medium-strong acid-base sites，and the introduction of Bi element promotes the dispersion of CuO in the carrier，and that the Cu/Bi component plays a synergistic catalytic decarboxylation role.

Materials Science & Technology

Influence of Ce Addition on Microstructure and Corrosion Resistance to Molten Aluminum of Fe-Cr-B Alloys



CHEN Weiping, LI Bing, LING Zicheng, et al

2021, 49(9):  73-79.  doi:10.12141/j.issn.1000-565X.200014

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Fe-Cr-B alloy has excellent corrosion resistance to molten aluminum，but its toughness is poor.In order to improve the toughness of Fe-Cr-B alloy，the influence of Ce addition （0~0.92%，mass fraction） on the microstructure，mechanical properties and corrosion resistance of Fe-Cr-B alloy in molten aluminum at 750℃ was investigated.The results show that the addition of Ce changes the boride structure in Fe-Cr-B alloy from a continuous network，dendritic and long rod-like structure to a short rod-like and block structure with less interconnection.With the Ce content increases，the alloy's impact toughness gradually increases，and the corrosion resistance to molten aluminum increases first and then decreases.The uniformly distributed short rod-like boride can improve the alloy's impact toughness while maintaining excellent corrosion resistance to molten aluminum.The Fe-Cr-B alloy with 0.59% Ce has the best comprehensive properties，its impact toughness is 187.97% higher than that of Ce-free，and its corrosion resistance to molten aluminum reaches 5.9 times that of typical die steel H13.

PTC Materials with Low Curie Temperature Point Based on Waterborne Acrylic Resin Matrix



LI Jing, HAN Shumei, LI Wenjun, et al

2021, 49(9):  80-87.  doi:10.12141/j.issn.1000-565X.200656

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Conductive polymer composites （CPCs） with positive temperature coefficient （PTC） have many applications in self-regulating heating fields.However，current researches on CPCs are mainly concentrated in the high temperature region，and few reports are concerned on low temperature segment.This study proposed a method of making a low Curie temperature point PTC material with water-based acrylic resin as matrix，and discussed the effects of temperature-controlled materials and different proportions of conductive fillers on Curie temperature.By adding Ni powder into the copolymer of water-borne acrylic resin and organic acid crystal，the PTC materials with low initial resistance and a Curie temperature point near the melting point of organic acid crystal were obtained.The Curie temperature point of the material can be adjusted within a certain range by regulating the proportion of Ni powder.Results show that，when the mass fraction of Ni powder is 30%，the initial resistivity of the material can reach 1.96Ω·cm，and the PTC intensity can exceed 6.Heating test results show that the heating capacity and electrical properties of the materials have no significant change after the thermal cycle，indicating good repeatability.

Crystallization Kinetics and Properties of Anatase Glass-Ceramic Glaze



PENG Cheng, SONG Xiaojiao, LIN Xiaoqing, et al

2021, 49(9):  88-94.  doi:10.12141/j.issn.1000-565X.200697

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A method for the preparation of anatase glass-ceramic glaze at the cooling stage was developed in this paper.The crystallization process of this glaze was analyzed by means of TG-DSC and XRD，and the crystallization kinetics was also studied.Experimental results show that the frit precipitates at the beginning of the heating stage，then melts at high temperature，and precipitates again at the cooling and soaking stages.The type and quantity of crystals precipitated in glaze are related to the thermal schedule at the cooling and soaking stages.Soaking at 700℃ is helpful to obtain crystalline glaze with more anatase phase.The crystallization activation energy of anatase calculated by Kissinger equation is 131.8kJ/mol and the Avrami index is 1.74.The crystallization of anatase occurs with a 3-dimension growth mode.The Vickers hardness of the glaze is 6.33GPa，which is comparable to that of traditional ceramic glazes.The glaze also shows good cleanability.In addition，the chemical composition greatly influences the properties of the glaze.The increase of TiO2 content improves the amount of crystallization of anatase，while the addition of Al2O3 adjusts the sintering temperature of the glaze，which makes it adaptable to the firing schedules of different types of ceramic.

Preparation and Application of Radiative Cooling Nanocomposite Fiber



ZHONG Mingfeng, CHENG Haixin, ZHANG Zhijie, et al

2021, 49(9):  95-100.  doi:10.12141/j.issn.1000-565X.200659

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By Using polymethyl methacrylate （PMMA） as the high-molecular polymer substrate and SiO2 as the filler，a kind of composite fiber with daytime radiative cooling function was prepared via electrospinning.Then，the XRD，SEM，TEM，UV-Vis-NIR and FT-IR were used to characterize the morphology，structure and optical properties of the composite fiber.The results show that the diameter of the electrospun composite fiber is about 800nm in diameter.The forbidden band width of pure PMMA fiber is 4.95eV，which makes the fiber do not absorb visible light; and the orientation crystallization in the electrospinning process leads to crystalline region and amorphous region in the fiber，which does not transmit visible light and displays white，thus obtaining a 200~2500nm short-wavelength reflectivity as high as 97.57%.After the electrospinning，nano-SiO2 powder particles with appropriate amount are dispersed in the composite fiber，which can greatly improve the emissivity.When the doping amount of SiO2 is 7.5%，the reflectivity of the composite fiber in the solar short-wavelength band of 200~2500nm and the emissivity of the 8~13μm atmospheric window are respectively up to 96.53% and 0.903.By using a self-made device to test the cooling effect in the actual environment，it is found that the composite fiber behaves good cooling effect，the temperature of the back of the composite fiber in the daytime is lower than the ambient temperature by 2~4℃.The proposed preparation method of composite fiber with inorganic powder and organic matrix provides a new solution to the practical application of radiative cooling.

Fluid Power & Electromechanical Control Engineering

Structural Design and Simulation Analysis of Bioaerosol Ultrafine Atomizer



ZHANG Zhen, YU Yusong, YANG Wenhui, et al

2021, 49(9):  101-108.  doi:10.12141/j.issn.1000-565X.210288

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In order to realize the rapid on-site detection for pathogens in complex biological hazards，it is necessary to prepare a variety of biological samples，establish a multimodal biospectral database，and eventually achieve targeted rapid inactivation of pathogens.Ultrafine atomizer design is a key technology to prepare high-quality biological samples.The technology can atomize liquid biological samples into small droplets，and then the bioaerosol particles can be formed after low-temperature freezing and sublimation drying.Through the optimal design of the air-assisted atomizer，the ultrafine and uniform atomization can be obtained under the conditions of low flowrate and low pressure without damaging the biological activity.In this paper，the spray process was simulated by means of RANS+DDM method，and the atomization characteristics of the air-assisted atomizer were analyzed at normal temperature and low temperature with heating power.At the same time，LES+VOF method was also adopted to test the turbulence effect of gas swirling near the nozzle on the liquid fluidics，and the atomization mechanism was analyzed.Moreover，the atomizing effect of the air-assisted atomizer was tested by an aerodynamic particle size tester.The results show that the air-assisted atomizer has good atomizing effect and can realize ultrafine atomization of particles with a diameter of around 1μm.The quality of biological samples prepared by spray-freeze-drying method can meet the design requirements，so it can effectively prepare bioaerosol samples in mass quantities and improve the detection and defense capability for pathogens on the site of biological hazards.

Numerical Research on Flow Distribution and Pressure Loss of Multi-Branch Pipeline Based on Confluence and Distribution



QIN Lei, ZHOU Fan, YANG Jiaxing, 等

2021, 49(9):  109-119.  doi:10.12141/j.issn.1000-565X.210281

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Confluence and distribution of multi-branch pipeline （CDMBP） can effectively reduce pipeline density and improve space utilization，but unreasonable structural design can easily cause too much pressure loss and excessive flow distribution difference.A numerical method for the optimal design about CDMBP is proposed in this paper.The paper studies the influence law of multiple parameters，including Reynolds number，outlet and inlet area ratio，closed cavity length at the end of the common chamber，branch pipe spacing and the number of branch pipes，on the flow distribution and pressure loss with parametric analysis.The results show that：there is a pre-ssure recovery zone in the confluence and diversion cavity，which has an impact on the flow distribution and pre-ssure loss of each branch; the Reynolds number has an impact on the flow distribution; the increase of the Reynolds number may increase the pressure loss and the difference of flow distribution; the influence of flow distribution and pressure loss from the length of the end common chamber is negligible; the outlet and inlet area ratio，branch pipe spacing，and the number of branch pipes are importantly related to flow distribution and pressure loss.These factors need to be comprehensively considered in the optimization design of the pipeline structure.These results can be used to guide the optimal design of the CDMBP.

Fluid Power & Electromechanical Control Engineering Special

Design and Precision Analysis of Buoyancy-Regulating Device with Multicylinder Structure



SONG Mancun, LI Guoqiang, ZHU Yi, et al

2021, 49(9):  120-125.  doi:10.12141/j.issn.1000-565X.210347

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Buoyancy regulating device can be used in unmanned underwater vehicles to realize the energy-saving rising，diving or suspending in the water.In this study，a buoyancy-regulating device with lager volume and high precision was designed with a five-cylinder structure.Firstly，the piston position was monitored by a displacement sensor and the telescopic characteristics of the multicylinder were assumed，so that the piecewise method of buo-yancy and the maximum possible error range were obtained.Then，based on the design and experiments of the prototype，the fact that the multicylinder tends to retain the characteristics after running was verified.Meanwhile，the piecewise method of buoyancy calculation was optimized to improve precision ability largely.Experimental results show that the prototype can meet the requirements of the continuous buoyancy regulating of 0~80L，the minimum regulating step of 1L，and the comprehensive precision of no less than 0.5%FS.

Dynamic Analysis of Two-Stage Planetary Roller Screw Mechanism Based on Parameter Matching



WU Linping, MA Shangjun, ZHANG Jianxin, et al

2021, 49(9):  126-134.  doi:10.12141/j.issn.1000-565X.210338

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By taking the two-stage planetary roller screw mechanism （PRSM） as the research object，this paper supplements the strength conditions and the stability requirements of the compressed rod required for its parameter design.And，on the basis of motion principle of the two-stage PRSM，the theoretical calculation methods of the rotation and revolution angular velocity of the rollers，the axial displacement and axial velocity of the nut at each stage are proposed.Then，according to the design parameters，a three-dimension model of the two-stage planetary roller screw mechanism is established，and a multi-body dynamics simulation model is constructed based on ADAMS software.By comparing the theoretical values with the simulation results，it is found that the relative errors are within the acceptable range，which verifies the rationality of the parameter matching of the two-stage PRSM and the accuracy of the theoretical calculation method.

Stress Cycle Behaviors of Planetary Roller Screw Mechanism Based on Kinematic Analysis



YAO Qin, LIU Yongshou, MA Shangjun, et al

2021, 49(9):  135-144.  doi:10.12141/j.issn.1000-565X.210291

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The movement and force transmission of planetary roller screw mechanism （PRSM） are realized by the planetary motion of multiple rollers and the meshing of their helical surfaces between the screw and the nut.Based on the characteristics of spatial helical surface of screw，nut and roller，the kinematic analysis model of PRSM is established by using the parametric equations of the screw，nut and roller in this paper.The positions of contact points are obtained according to the principle of continuous tangency.Then，the relationship between the structu-ral parameters of PRSM is deduced from the kinematics characteristics of the contact points.On this basis，the spatial motion trajectories of the screw，nut and roller are simulated，and the stress cycle behaviors on their threads are further obtained.Furthermore，the working life of the PRSM is predicted.The results show that there is a relative velocity at the contact point of the screw and roller，and the contact point of the nut and roller is the instantaneous center; and that each specific contact point on the roller and nut bears stable pulsating cyclic contact stress，while each specific contact point on the screw is subjected to cyclic contact stress with periodic amplitude variation.