Table of Content

25 December 2019, Volume 47 Issue 12

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Mechanical Engineering

Deep-Learning Recognition of Workpieces Based on Cloud and Fog Computing



YAO Xifan, LAN Hongyu, TAO Tao, et al

2019, 47(12):  1-8.  doi:10.12141/j.issn.1000-565X.180161

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Traditional industrial automatic sorting method is confronted with the problems such as low accuracy of workpiece identification and complex definition of features． Although deep-learning provides a good solution to such problems，there remains the problem of high computational requirements for edge-end equipment． Thus a deep- learning recognition algorithm based on fog and cloud computing was proposed，in which an improved ALEXNET convolution neural network ( CNN) is used for training in the cloud． Then，the trained CNN is downloaded to the fog ( edge) device to recognize workpieces in real time． The results of the experiment carried on 100 different workpieces show that accuracy of the proposed workpiece recognition algorithm is improved from 98% of ALEXNET to 99% ，and the model parameters are reduced by 25% ． The workpiece recognition algorithm can fully utilize the powerful cloud computing capabilities and the real-time nature of edge devices，and provide a novel way for intelli- gent recognition of workpieces．

Influence of Structural Parameters of Ｒigid-Flexible Composite Gears on its Dynamic Characteristics



LI Junyang, WANG Bo, WANG Jiaxu, et al

2019, 47(12):  9-16.  doi:10.12141/j.issn.1000-565X.190081

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Rigid-flexible composite gear is a new type of gear with high reliability and precision transmission through adaptive deformation coordination of internal flexible components． In order to explore the influence of the coordination parameters of composite gear deformation on its dynamic characteristics，the virtual prototype of rigid- flexible composite gear pair was established by ADAMS based on the establishment of the comprehensive meshing stiffness model． The influence of the gap between the ring gear and the hub，the center distance of the gear pair， the elastic modulus of the metal rubber on the dynamic characteristics of the compound gear ring acceleration，an- gular acceleration，meshing force and dynamic transmission error were analyzed． The simulation results show that the reduction of the center distance of the gear pair not only diminishes the angular acceleration of the ring gear and the hub，but also the meshing force of the gear pair． What’s more，the transmission precision is also improved． The increase of the elastic modulus of the metal rubber can effectively suppress the vibration acceleration of the ring gear，but the meshing force increases． The gap between the ring gear and the hub increases，the acceleration of the ring gear increases，the transmission error increases，and the angular acceleration decreases． Combining the above factors，reducing the center distance of the gear pair and the gap between the ring gear and the hub，increasing the elastic modulus of the metal rubber can reduce the vibration of the composite gear and improve the transmission ac- curacy．

Analysis on the Influence Factors of Pneumatic Servo-Mechanism's Characteristics



YIN Yaobao, LIANG Junzhe, YUAN Jiayang, et al

2019, 47(12):  17-24.  doi:10.12141/j.issn.1000-565X.180128

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The principle of the pneumatic servo that composed of pressure reducing valve，solenoid valve，single- flapper valve，single acting cylinder was analyzed，and its mathematical modeling was also built． The influence fac- tors of pneumatic servo-mechanism were analyzed based on the different altitude． The results show that the air sup- ply temperature，ambient temperature and air supply pressure have small influence on the characteristics of the ser- vo-mechanism． When altitude rises，the back pressure of the pneumatic system decreases，resulting in a significant change in the working point of the servo-mechanism．

Numerical Simulation for Hole-drilling Strain Gage Method Applied on Curved Surface



MA Xiaoming OU Qingyang

2019, 47(12):  25-31.  doi:10.12141/j.issn.1000-565X.180299

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Hole-drilling method is a mechanical way with high accuracy to measure residual stress on surface． The existing analyses and studies on hole-drilling standard are wholly based on large plane surface，while there is little research on surfaces with curvature，such as the surface of fillet weld or tubes． Thus the objective of this study is to clarify the influence of surface shape on the residual stress level． When the material parameters are fixed，the sur- face shape have direct influence on the calibration constants a and b． Based on the mechanics elasticity，the com- parative analysis of borehole cross-section of the plane surface and spherical surface were carried out． The result shows that stress relief difference is caused by factor Dh，which is the distance from the strain gauge to the edge of the hole． Then the drilling process of concave and convex spherical models with different curvatures were simulated by finite element model ANSYS to quantify the stress relief of different models． The simulation results are consistent with the changing regularity of Dh and hole depth． In addition，based on the results of spherical coefficients，a cal- culation scheme for general revolution surface was presented，which may be applied to all kinds of surfaces includes cylinders．

Analysis Method of Electrode Ignition Loss State in Enameled Wire Ｒesistance Spot Welding



ZENG Jiaquan, CAO Biao, YANG Kai, et al

2019, 47(12):  32-37.  doi:10.12141/j.issn.1000-565X.190191

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Analysis method of ignition loss state was studied，aiming at the the problem of lacking quantitative as- sessment for electrode ignition loss in enameled wire resistance spot welding． Feature analysis was carried out by choosing dynamic resistance of electrodes as process information research object，and maximums of dynamic resist- ance during every ohmic heating process and the change rate with respect to the number of ohmic heating were ex- tracted as features of ignition loss state through． Analysis methods of ignition loss state based on state division and grey prediction were proposed and applied to analyze ignition loss experiments． The result shows that the chosen features can reflect ignition loss state of electrodes efficiently． Besides，the change of ignition loss state can be rec- ognized sensitively with the proposed methods，and different stages of ignition loss process can be analyzed quantita- tively without complex calculation and models trained and tested beforehand． Therefore，such methods can offer ref- erence for analysis research on electrode ignition loss in enameled wire resistance spot welding．

Pedestrian Head Protection Performance Simulation of Chiral Honeycomb Sandwich Conceptual Engine Hood



YANG Shu, JIANG Feng, DING Hongfei, et al

2019, 47(12):  38-42,61.  doi:10.12141/j.issn.1000-565X.180576

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A conceptual design of energy-absorbing sandwich engine hood with tetra-chiral honeycomb core was proposed to reduce pedestrian head injury in car accidents． Finite element models of the headform impactor，the tetra-chiral honeycomb and the traditional hexagonal honeycomb sandwich energy-absorbing engine hoods were con- structed． The performances of the two types of hoods for pedestrian head protection were simulated and compared． The results show that，compared with hexagonal honeycomb，the tetra-chiral honeycomb sandwich engine hood can reduce the head collision injury more effectively． The tetra-chiral honeycomb core energy-absorbing sandwich en- gine hood can provide reference for new energy-absorbing engine hood design for pedestrian head protection in car accidents．

Architecture & Civil Engineering

Horizontal Compressive Capacity of the Joints for the New Type Nested Steel Tubular Scaffold



SHI Kairong, XU Jiebin, JIANG Zhengrong, et al

2019, 47(12):  43-52.  doi:10.12141/j.issn.1000-565X.190240

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The new type nested steel tubular scaffold has advantage in safety，cost and convenience compared with traditional scaffolds，but its lack of theoretical research hinders its promotion and further application． Experimental research and finite element analysis of horizontal compressive loading cases under three different working conditions were carried out，with the joints of the new type nested steel tubular scaffold as the studying objects． The research shows that the experiment results and finite element simulation results are basically consistent． And along with the increasing of horizontal loading，the displacements of joints in all three cases increase linearly first，but later on they performs obvious nonlinearity as soon as the yield of joints appear． The failure modes of axial compression and biaxial asymmetric compression are bending failure and squashed section of standing tube． As for biaxial symmetri- cal compression，the failure mode is squashed section of standing tube and loose connection between wedge head of ledger and cruciform nested socket． Therefore，the compressive stiffness and compressive capacity of the joint de- pend on the loading method． On this basis，pressure resistance parameter of the joint was systematically analyzed． The result shows that the most influential factor is the length of standing tube，while the thicknesses of wedge head of ledger and cruciform nested socket have less influence． Thus the compressive stiffness model in term of the length of standing tube was presented．

Experimental Study of Bonding Properties Between GFＲP Bars and ECC After Freezing-melting Circulation



WU Lili, JU Xiangkai, CONG Qiming, et al

2019, 47(12):  53-61.  doi:10.12141/j.issn.1000-565X.190199

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The combination of engineering cementitious composites ( ECC) and glass fiber reinforced composites ( GFＲP) can effectively improve the durability of structures ，but the research of bond durability between GFＲP and ECC was rarely reported under the environment of freezing-melting circulation． 42 specimens divided into 9 groups were designed herein． Quick freezing method was adopted to investigated the changes of the weight loss rate， the transverse relative dynamic modulus of elasticity of ECC，bond strength between GFＲP and ECC compared with the ordinary concrete after 75 freezing-melting circulation，and the bond-slip curves of specimens were also ana- lyzed． The results show that the antifreeze quality of ECC is superior to that of the ordinary concrete，and the bond- ing property between ECC and GFＲP bars of strength grade C30 and C50 are 3. 0 times and 4. 3 times of that ordi- nary C30 concrete and GFＲP bars respectively after 75 times freezing-melting circulation． The pull-out test results were fittingly compared with the analytical models including mBPE model，CMＲ model and continuous curve mod- el，thus the corresponding fitting parameters and fitting correlation coefficients were obtained，and the study shows that the CMＲ model provides better fitting prediction．

Neutral Axis Position-Based Monitoring Method and Indicator for Structural Evaluation of Concrete Girder Bridges



XIA Ye, WANG Peng, LEI Wei, et al

2019, 47(12):  62-71.  doi:10.12141/j.issn.1000-565X.190174

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Short and medium span bridges are widely spread and extremely large in number． The safety and dura- bility of concrete beam bridges，as a major portion of all bridge types，are very important． A neutral axis position based monitoring method is proposed，and the corresponding index system and evaluation framework are constructed to evaluate the performance deterioration and safety reservation． Through theoretical and finite element analysis，the parameter characteristics and deterioration law of neutral axis index are investigated regarding various stress state of reinforced concrete beam at different prestressing levels． A structural health monitoring system has been installed and operated in real bridges to evaluate the overall performance of neutral axis index system． Neutral axis index is estimated and statistical analysis is carried out based on the observed response data． Ｒesults show that the neutral axis index system can effectively characterize the degradation and damage development of the structure，and the proposed method can benefit for bridge design and management，thus has potential value for practical populariza- tion．

Building Energy Consumption Information Model for Big Data Analysis



MA Zhiliang TENG Mingkun REN Yuan

2019, 47(12):  72-77,91.  doi:10.12141/j.issn.1000-565X.190170

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To utilize building energy consumption monitoring data of various granularity for big data analysis，indi- cators on building energy consumption were collected from national standards，guidelines and existing research． Da- ta used to calculate those indicators and the interrelationships of these data were identified． By using object-oriented method，an overall model of building energy consumption information was established and the information model of building energy consumption monitoring data of different granularity for big data analysis was built from three as- pects，forming the building energy consumption information model． Based on the model，the MongoDB database management system is used to establish a database for big data analysis to verify the feasibility of the model． This study makes it possible to make full use of building energy consumption monitoring data of different granularities for big data analysis．

A Greedy Heuristic-based Approach to Solving the Discrete Unit Disk Cover Problem



Miao WANG Song-Tao WU Yong-Zhe LI

2019, 47(12):  78-85.  doi:10.12141/j.issn.1000-565X.190370

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The current urban complex model proposed by the sharing economy has a limited service radius. The basic mathematical model for selecting the location of a complex is a discrete unit disk coverage (DUDC) problem. Given n points in a plane and unit disks with radius r, the objective of the DUDC problem is to determine a minimum number of the disks to cover all points. This paper presented an approach, which makes use of a greedy heuristic-based algorithm, to get the approximate optimal solution for the DUDC problem within polynomial time. The presented approach generated discrete cells to represent the 2D plane. Then, unit disks can be placed at the center of cells. Target points covered by the disks can be used to generate basic sets. A greedy algorithm was articulated to find a minimal combination of the covering sets that facilitates the realization of full coverage of all target points. The center of the minimal covering circles regarding the points in the sets was calculated and considered as the positions of the disks. Based on a case study, the effectiveness of the proposed algorithm has been validated. The factors that influence the performance of the algorithm were also discussed.

Materials Science & Technology

Chromatic and near-infrared reflective properties of Zn2+ doped CaCuTi4O12



2019, 47(12):  86-91.  doi:10.12141/j.issn.1000-565X.190123

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This paper adopted conventional solid state reaction route to prepare a new-type inorganic pigment CaCu(3-x)ZnxTi4O12 with high near-infrared reflective properties. The structure, colour and reflective properties were investigated by XRD, Color-Eye automatic differential colorimeter and UV-vis-NIR spectrophotometer. Result showed that crystal structure changed from single phase to multi-phase with the increase of substitution degree. With the increasing of doping amount of Zn2+ ions(x=0.00-0.06), the band gap increase from 2.16eV to 2.26eV, the yellow hue b* increases from 22.35 to 29.62, and the near infrared reflectance ratio increases from 52.3% to 62.3%. The near-infrared reflectance of CaCu3Ti4O12 and CaCu2.4Zn0.6Ti4O12 pigments coating are 46.4% and 55.2% respectively. The pigments also have chemical stability and thermal stability. Therefore, the prepared CaCu(3-x)ZnxTi4O12 pigments have great application potential in “cool colorant”.

Study on the Effect of Molding Pressure on the Mechanical Properties of GRC



2019, 47(12):  92-98,105.  doi:10.12141/j.issn.1000-565X.190239

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In this paper, the effects of molding pressure, water-to-binder ratio and load-holding time on the flexural strength and fracture energy of premixed casting GRC were studied. The results show that the effects of various factors on the flexural strength and fracture energy of GRC are different. The higher the molding pressure, the higher the flexural strength and the lower the fracture energy of GRC. Under pressure forming conditions, the flexural strength of GRC does not change significantly with the increase of water-to-binder ratio, but the fracture energy increases greatly with the increase of water-to-binder ratio. With the prolongation of load-holding time, the flexural strength of GRC increases slightly, but the fracture energy changes little. The fracture energy of GRC decreases with the increase of molding pressure when the glass fiber content is different. The empirical formula obtained by fitting the experimental data can better reflect the relationship between GRC fracture energy ( of different glass fiber content and pressure-free GRC fracture energy ( ) and molding pressure (F) under the experimental conditions.

Synthesis of CuCl2-Graphite Intercalation Compounds in Molten Salt and Their Formation Mechanism



2019, 47(12):  99-105.  doi:10.12141/j.issn.1000-565X.190071

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CuCl2-graphite intercalation compounds (CuCl2-GICs) were synthesized in molten CuCl2. The effects of the reaction time and the ratios of the reagents on the stage structure, morphology and electrical properties were investigated in detail. The results show that the synthesized products are mainly the CuCl2-GICs with mixed stages of stage 1 and other stages. Small amounts of graphite are also found in the products. When the reaction time increases, the intercalation effects are enhanced. However, the variations of the ratios of the reagents show little effect on the microstructure of the CuCl2-GICs. The morphology observation indicates that the graphite flakes expand after the intercalation and amounts of CuCl2 are found on the edge of the graphite flakes. The EDS elemental analysis demonstrates that the copper chlorides are nonstoichiometry with a lot of [Cl-] deficiency. The electrical conductivity of the CuCl2-GICs improves when compared to those of the original graphite and a maximum of 80% improvement is achieved.

Advance in Colloidal Green Quantum Dot Material



TANG Liwen MAO Weiguo LI Ling

2019, 47(12):  106-115.  doi:10.12141/j.issn.1000-565X.190223

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Food Science & Technology

Advance in Proteins as Microcapsule Wall Materials



LOU Wenyong ZHONG Shurui ZHANG Zhihua PENG Fei ZENG Yingjie

2019, 47(12):  116-125.  doi:10.12141/j.issn.1000-565X.190424

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Copper(II)-coordinating Force and Antioxidant Activity of Neohesperidin Dihydrochalcone



2019, 47(12):  126-132.  doi:10.12141/j.issn.1000-565X.190244

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Flavonoids often improve their biological activity after having coordinated with metal ions. In this paper, the coordination ratio of the complex of neohesperidin dihydrochalcone(NHDC) with copper(II) was studied by the method of molar ratio and continuous coordination in equal molar solution. Before and after the coordination, the complex structure was studied by UV, IR and X-ray diffraction. DPPH method, salicylic acid method and FRAP method were used to compare the variation of antioxidant activity. Results indicated that the coordination ratio of NHDC to copper was 2: 1, the stability of the NHDC-Cu (Ⅱ) complex was greatly affected by pH and the most stable state was at pH 7.0. The hydroxyl radical-scavenging activity was significantly enhanced possibly due to the improvement of water solubility and the increase of the amorphous degree after coordination with copper. And the increase of water solubility and bioavailability after NHDC coordination was attributed to the "concentrated effect" of copper on NHDC non-sugar ligand and the "embedding effect" of sugar part on the non-sugar part after NHDC coordination. However, there was no significant changes for scavenging fat-soluble free radicals like DPPH· and total reduction force by NHDC or its complex with Cu2+.

Effect of NaCl on Self-assembly Interaction Between Chitooligosaccharide and Pectin



2019, 47(12):  133-141.  doi:10.12141/j.issn.1000-565X.190284

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Effects of NaCl and its concentration on electrostatic self-assembly behavior between chitooligossacharide and pecin were investigated through measurement of turbidity and ζ-potential of chitooligassacharide/pecin complex solution, and analysis of macroscopic and microscopic state of complex solution and turbidity titration procedure with the study on analysis of ATR-FTIR spectrum and ultrastructure of PEC by SEM and TEM. The results showed that NaCl hindered the self-assembly interaction between chitooligossacharide and pectin resulting in decrease of pHc、pHФ and pHprep values. The turbidity of complex solution decreased in phases and the solution became clear with NaCl concentration increasing; meanwhile, the amount of PEC formed decreased and PEC changed to small even nano-particles (NaCl concentration of 30 mM or more) from networks. At NaCl concentration below 10 mM, the intermolecular electrostatic repulsion of pectin decreased and pectin chains became properly flexible and could be rolled and folded to form larger particles with chitooligosaccharide. Further increasing of NaCl concentration, however, led to increase ofζ-potential absolute around the surface of PEC particles and electrostatic repulsion interaction among the particles, which resulted in a better packing of more flexible and coiled pectins with chitooligosaccharide to form more dispersive and less particles. The ATR-FTIR result of PECs implicated that the interaction between chitooligosaccharide and pectin was not changed by addition of NaCl, but intensity of the interaction was. The modes of self-assembly interaction between chitooligosaccharide and pectin at various NaCl concentrations were suggested at the end of this paper.

Effect of Pulsed Electric Field on the Texture and Impregnation Rate of Kumquat Compote#br#



2019, 47(12):  142-148.  doi:10.12141/j.issn.1000-565X.190443

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Abstract: The research is mainly focusing on the effects of Pulse Electric Field (PEF) on the Cortical structure and impregnation rate of kumquat. The more the number of PEF treatments is applied,the faster the sugar concentration in the impregnated solution decreases. The results of orthogonal experiment indicated that the best condition is treated 4 times by 1.5 kV/cm electric intensity and 40 pulses,compared with traditional way the impregnation rate increases 78.49%,the immersion time can be reduced by 6～7 days.The experimental results indicated that better resilience and chewiness can be achieved. Compared with the kumquat treated by the traditional way,the properties of PEF treatment which chewing increased 76.36 %～83.33 % and the resilience increased by 10.31 %～15.33 %.