bluuebunny/crossref_metadata_2025 huggingface dataset:
Highly Concentrated Hydroxyapatite Suspension for DLP Printing
Authors: Yao Yongxia , Sha Na , Zhao Zhe
Published: November 2019

Due to the lack of commercially available high-quality hydroxyapatite (HA) powder, it is still rarely reported by the literature concerning the development of UV resin for digital light processing 3D printing. The previous studies still had the problem of delamination and also poor sintering performance led by low solid-load slurry. Here low viscosity and high solid-load hydroxyapatite (HA) UV resin suspensions were developed for digital light processing 3D printing. In this study, the effect of the type of dispersant, the dose levels of dispersant and the solid load of HA powder on the rheology properties were thoroughly investigated to obtain a flowable highly-concentrated HA UV resin suspension. Finally, a 40vol% slurry with viscosity of 3.7Pa·s at a shear rate of 10 s-1 was successfully developed. After 3D printing and sintering, a dense ceramic with relative density of 95.85% can be obtained at a sintering temperature of 1300°C.
Mechanical Properties of ZrO2 TPMS Structures Prepared by DLP 3D Printing
Authors: Shen Minhao , Wang Cao , Zhao Zhe
Published: November 2019

Compressive strength is one of the most important mechanical properties for cellular ceramics. But the dependence of compressive strength of highly porous cellular ceramic structures on porosity remains unclear due to the limit of available methods for making such strong structures based on specific structural designs. In this paper, the TPMS structures, namely P-cell, and neovius structure, were prepared based on the DLP 3D printing technology. Samples with various unit cells were fabricated with zirconia. The relative density of the sintered samples exceeds 99%. The effects of cell number on the compressive strength and deformation of the model were investigated. Samples with similar relative densities exhibited comparable mechanical property in aspect of compressive strength. It is very interesting that the cell number eventually only influence the total strain.
ZTA Ceramic Materials for DLP 3D Printing
Authors: Sun Ying , Wang Cao , Zhao Zhe
Published: November 2019

As a new additive manufacturing method, DLP has the advantages of high precision, fast speed and low cost. ZTA ceramic is anticipated to be used in more applications due to its superior bending strength, fracture toughness and thermal conductivity. But the detailed study with ZTA printing material for DLP is still rarely reported. In this experiment, ZTA ceramic UV resin with various ZrO2 concentration (5-15wt.%) were investigated and tested for their 3D printing performance. ZTA ceramic UV resin with low viscosity (<3Pa·s at shear rate of 10s−1) and high solid load (55vol.%) were successfully developed. After sintering at a temperature of ⩾ 1600°C, a relative density of >96% can be always promised. For the optimized doping level of ZrO2 at 11wt%, a density of 99% can be achieved.
XFEM Analysis of the Effect of Fiber Volume Fraction on Crack Propagation in Fiber Reinforced Ceramic Matrix Composites
Authors: Fang Guangwu , Gao Xiguang , Song Yingdong
Published: November 2019

The mechanism of crack propagation near the interphase plays an important role in the failure procedure of ceramic matrix composites. The aim of this paper is to examine the effect of fiber volume fraction on the crack propagation. A three-phase unit-cell model was used to describe the micro-structure of fiber reinforced ceramic matrix composites. The interphase between fiber and matrix was modelled as a finite-thickness cylinder around the fiber. The extended finite element method (XFEM) was applied to simulate the crack initiation and propagation in the unit-cell. Without the definition of crack path priori, the approach based on XFEM can simulate the arbitrary path of cracks growing in the composites. The crack patterns and stress-strain responses for different fiber volume fraction were compared. In particular, the penetration/deflection mechanism when the matrix cracks grow to the interphase was analysed and compared. The results show that the initiation and propagation of the secondary crack/cracks were significantly influenced by the fiber volume fraction.
Preparation and Characterization of An All Oxide Ceramic Matrix Composite by A Novel Method
Authors: Liang Yanyuan , Ma Xin , Qiu Haipeng
Published: November 2019

Due to the characteristics of high temperature oxidation resistance and high reliability, all oxide composites are ideal materials for components in hot end of aeronautics and astronautics. In this paper, all oxide ceramic matrix composite(CMC) was prepared by a novel method which combined warm pressing of prepreg with PIP using polysilialumoxane as the precursor of mullite. The morphology, structure and mechanical properties of the all oxide CMC were characterized. The results show that polysilialumoxane with a ceramic yield of 53wt%can be completely changed to ceramic at 1200°C and form mullite crystals. The composite with alumina and mullite matrix derived from alumina powder slurry indicated the best mechanical properties, the flexural strength and fracture toughness of the composite reach 208.3Mpa and 128.6Mpa respectively, and the pull-out effect of the fibers is obvious in the process of tensile fracture, and the composites show ductile fracture. whereas the mechanical property decreases significantly after heating at 1200°C for100 hours due to the densification of matrix and abnormal growth of alumina grains in fibers.
Study on Interlaminar Shear Properties of SiO2f/SiO2 Composites Based on Different Braided Structures
Authors: Shi Jiang , Sheng Wang Hong , Wei Qi Hong , Wei Xu Chuan , YangWei Hua , Su Tong , Jun Liu Xiao , Qiu Gao Wen , Tao Shao Chang , Dan Xu Dan
Published: November 2019

The interlaminar shear properties of SiO2f/SiO2 composites reinforced by needle-punched and 2.5D braided preforms are studied and analyzed. The effects of different temperatures and braiding structures on the interlaminar shear strength were investigated by analyzing the stress curves, macrostructure and microstructure of the composites. The increase of temperature, in a certain range, will change sintering condition of matrix and the bonding between matrix and interface, and thus increase the interlaminar shear strength. Because of the different shape of warp and weft yarn, there is a considerable discrepancy in the interlaminar shear strength of different direction. The interlaminar shear strength of needle-punched braided SiO2f/SiO2 composites is a little higher than the warp direction of 2.5D braided SiO2f/SiO2 composites. The interlaminar shear strength, time and economic cost should be considered comprehensively to select a more suitable braiding structure.
Development of the Environmental Friendly Non-Aqueous Tape Casting Process for High-Quality Si3N4Ceramic Substrates
Authors: Hou Qingdong , Luo Xudong , Xie Zhipeng , An Di , Xiao Zhicai , Ma Bin
Published: November 2019

A cheap and environmental friendly non-aqueous tape casting process for preparing high quality Si3N4ceramic substrates was explored. A ternary solvent mixture of ethanol, ethyl acetate and butyl acetate-based formula was developed by using castor oil, polyvinyl butyral and dibutyl phthalate as the dispersant, binder and plasticizer, respectively. The influence of dispersant content, binder content and solid loading on the rheological properties of Si3N4slurries was firstly investigated. It was found that the optimized formulation for dispersant, binder and solid loading was 1.6 wt%, 12 wt% and 51 wt%, respectively. The flat, flexible and uniform green tapes with a thickness of 400–500 μm and high-quality including high bulk density, uniform pore distribution and low porosity were obtained. After drying and debinding, the green sheets were sintered at 1900 °C for 2 h, where Si3N4ceramics with a thermal conductivity being 85.79 W·m−1·K−1can be achieved. The sintered samples were one of the most attractive substrate materials for high power electronics applications.
The Study of High Strength Reticulated Vitreous Carbon Preparation Method
Authors: Yan Dachen , Chen Yufeng , Zhang Shichao , Sun Haoran , Sun Xiankai , Fang Kai , Tao Liushi
Published: November 2019

Reticulated vitreous carbon (RVC) is a very promising functional material but the lower strength of foamed carbon greatly limits its application range. In order to increase the strength of the reticulated vitreous carbon, we used to add graphene during the preparation process because of its high strength. The foams were manufactured by multiple replication of a polyurethane foam template structure using ethanolic solutions of phenolic resin and graphene. Then the foams of preparation were carbonized in an inert atmosphere 700°C-1000°C by polyurethane foam impregnated with phenolic resin precursor. The proper addition of graphene was sought by testing the mechanical properties of the reticulated vitreous carbon and observing its microstructure. The results show that the addition of graphene could improve the mechanical properties of reticulated vitreous carbon.
The Microstructure and Shear Strength of SiC Joints Brazed with SiC Particle Reinforced Si-24Ti Alloy
Authors: Li Zhen , Wen Qun , Zhong Zhihong , Wu Yucheng
Published: November 2019

To refine the microstructure and increase the joint strength of SiC ceramic brazed with Si-24Ti (wt.%), carbon nanotubes (CNT) were added into Si-24Ti brazing alloy to form SiC particles in the braze zone. The effect of the amount of CNT in the brazing alloy on the microstructure and shear strength of joints was investigated. The microstructure and element distribution of the joint was studied by scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS). The results indicated that the addition of the proper amount (1-3 wt.%) of CNT could refine the microstructure of joints and achieve high-quality SiC joints. The shear strength of the joint brazed with 3 wt.% CNT addition reached the maximum value of 108 MPa, which was 21.3% higher than that of without CNT (89 MPa). However, when the amount of CNT increased to 5 wt.%, the shear strength of joint decreased to 55 MPa, due to the formation of cavity in the joint. The strengthening mechanism of in-situ formed SiC particle in the composite brazing alloy was evaluated.
Erosion and Wear Resistance of Cr3C2-NiCr Composite Ceramic Coating for Gun Barrel
Authors: Men Xiangdong , Tao Fenghe , Gan Lin , Li Yue , Liu Zhe
Published: November 2019

A Cr3C2-NiCr coating was prepared on the PCrNi3MoVA steel via HVOF for the further use in gun barrel to reduce the wear and erosion of the PCrNi3MoVA steel. The microstructure and interfacial bonding state of the coating were analyzed by scanning electron microscopy (SEM). The erosion resistance of the coating was tested by high-speed hot airflow generated by a modified pressure-vented vessel. The high temperature friction coefficient and high temperature wear resistance of Cr3C2-NiCr coating and PCrNi3MoVA steel substrate were compared by high temperature friction and wear test. Results show that the Cr3C2-NiCr coating combines well with PCrNi3MoVA steel without cracking and shedding. The coating does not fall off under high-speed airflow erosion yet with an oxidation of the surface. The high temperature wear resistance of Cr3C2-NiCr coating is significantly better than that of PCrNi3MoVA steel substrate.
Preparation and Characterization of Transparent Glass Ceramics Containing Na3Gd(PO4)2
Authors: Chen Xi , Zhang Hongbo , Zou Xiangyu , Su Chunhui
Published: November 2019

Transparent glass ceramics with the mole percent composition of 21.3Na2CO3-2.2Gd2O3-38SiO2-36.5H3BO3-2.0P2O5 were prepared by melting crystallization method. The heat treatment system, crystal phase, micromorphology and transmittance of the samples were tested and characterized by differential scanning calorimetry analysis(DSC), X-ray diffraction (XRD), scanning electron microscopy(SEM) and UV-Vis-NIR, respectively. The optimum heat treatment condition is 730°C for 2h. The Na3Gd(PO4)2 crystal phase were precipitated homogeneously among the glass matrix. The results of FTIR spectra confirmed the presence of PO4 groups in the glass ceramics samples. The refractive index of glass ceramics and glass samples were measured. In the visible region, the transmittance of glass ceramics is up to 80%.
Fabrication of Silicon Nitride Fiber Materials by Organic Foam Impregnation Method
Authors: Wang Gang , Zhang Qi , Han Jianshen , Zhao Xin , Li Hongxia
Published: November 2019

In this paper, porous silicon was prepared by organic foam impregnation, and silicon nitride fibers were prepared by direct in-situ nitridation of porous silicon. The effect of pore structure of porous silicon on material properties was studied. The results show that the silicon nitride fiber material with low density, high strength and low thermal conductivity can be obtained by using organic foam impregnation method. The pore size of template has a certain effect on the growth of silicon nitride fibers. The smaller the pore size of the template, the higher the content of silicon nitride in silicon nitride fiber material. This is due to the concentration of gas phase reactants in pore.
Fabrication of Al2O3-Bonded Fibrous Ceramics by An Aqueous Gel-Casting Process
Authors: Liu Zhenli , Yu Jingkun , Tian Chen , Li Chaoyue , Yuan Lei
Published: November 2019

The traditional gel-casting method mostly uses organic compounds, which are complex process, expensive and pollute the environment. In order to overcome the disadvantage of the traditional gel-casting method, an environment friendly aqueous gel-casting process is introduced in this paper. Al2O3-bonded fibrous ceramics with high porosity and low thermal conductivity have been prepared by a novel hydrated alumina gel-casting process using the ρ-Al2O3and mullite fibers or YSZ fibers as raw materials and the deionized water as hydration agent. A bird-nest-patterned three-dimensional reticular skeleton structure was established by the fibers to ensure a certain mechanical strength. The effects of the amount of mullite fibers andYSZ fibers on the properties of porous ceramic, such as phase composition, microstructure, sintering behavior and relative properties were investigated. Results showed that the as-prepared Al2O3-bonded fibrous mullite ceramics have high porosity of 66.9%∼78.6%, low thermal conductivity of 0.236∼0.479 W/m·K, and relatively high compressive strength of 0.80∼2.78 MPa. The as-fabricated fibrous YSZ ceramics had a high porosity (71.1%∼72.7%), a low thermal conductivity (0.209∼0.503 W/m·K) and a relatively high compressive strength (3.45∼4.24 MPa). Comparing to the as-fabricated fibrous mullite ceramics, the compressive strength of as-fabricated fibrous YSZ ceramics is promoted obviously.
Magnesium Phosphate Cements/GNPs Composites by Combustion Synthesis and Acid-Base Reaction
Authors: Lu Nan , Liu Jiaxi , He Gang , Li Jiangtao
Published: November 2019

Magnesium phosphate cements (MPC)/graphene nanoplatelets (GNPs) composites were fabricated by combustion synthesis and acid-base reaction. MgO/GNPs mixture powders were obtained by the combustion reaction between Mg powders and CO2 gas. The composites were prepared by mixing MgO/GNPs mixture powders with potassium dihydrogen phosphate (KH2PO4) using borax as retarder. The effect of GNPs content on mechanical and functional properties of the prepared MPC/GNPs composites was investigated. The results show that this MPC/GNPs cements mainly consisted of MgO and KMgPO4•6H2O. Moreover, the crystallinity of KMgPO4•6H2O in lower surface is better than the upper surface due to the difference of temperature. With incorporating small amounts of GNPs into MPC, the spectral absorptivity of the composite was improved to 0.95 in most spectral regions. Nevertheless, the compression strength shows little change with changing the GNPs content, which may be attributed to use coarse MgO powder as reactant. In virtue of short processing time and homogeneous distribution of GNPs, the novel fabrication provides a new route for preparing GNPs-cement based composites.
In-situ Synthesized Mullite Whiskers on the Surface of Aluminum Silicate Fibrous Felts with Low Thermal Conductivity and High Compression Rebound Performance
Authors: Liu Jiapeng , Guo Anran , Liu Jiachen , Hou Feng
Published: November 2019

In this study, in situ synthesized mullite whiskers on the surface of aluminum silicate fibrous felts was prepared by gas-phase deposition and reaction. Effects of the concentration of impregnation solutions on the density, thermal conductivity, microstructure and the compression rebound performance of the fibrous felts during the in situ synthesized mullite whiskers process were analyzed. The mullite whiskers were generated on the surface of aluminum silicate fibrous felts through gas-phase deposition and reaction of AlOF and SiF4, which proved that the mullite whiskers could form on the aluminum silicate fibers in this process. The results showed that the materials fabricated at the optimum process showed a high compression resilience ratio (94.6%) after compression to a compressive strain of 10%, meanwhile the density and the thermal conductivity of the sample fabricated at the optimum process were 0.1536g/cm3 and 0.04102 W/(m*K), respectively.
Near-Infrared Emission Property of ZrC-TiC Solid Solution Prepared by Combustion Synthesis
Authors: Li Honghua , Shuang Shuang , He Gang , Yang Zengchao , Li Jiangtao
Published: November 2019

ZrC-TiC solid solutions are considered as a promising candidate for ultra-high-temperature structural applications. Zr
x
Ti1-x
C (x=0, 0.2, 0.4, 0.6, 0.8, 1.0) solid solutions have been prepared by combustion synthesis method using Zr, Ti and C elemental powder. The effect of Zr/Ti mole ratio on the phase composition, microstructure, oxidation resistance and near-infrared emission property of the synthesized samples were investigated. It was found that the prepared samples with different Zr/Ti mole ratio all have formed a single cubic structure. The grain size of Ti rich solid solution developed to a larger size than that of Zr rich samples. Zr
x
Ti1-x
C solid solution with x=0.4 has a higher starting oxidation temperature of ∼650°C than that of the other solid solution samples. The prepared solid solution with x=0.4 also shows the largest emissivity of 0.79 in 0.75-2.5μm and 0.76 in 3-5μm wavelength range. The prepared Zr
x
Ti1-x
Csolid solution samples by combustion synthesis method, which exhibit good near-infrared emission property could be regard as a promising ablation resistant material.
Electrical Conduction and Impedance Behavior of Sr0.97Ti0.6Fe0.4O3-δ Electrode Containing YSZ for Various Applications
Authors: Yi Zhong-Zhou , Zhai Fengrui , Li Nan , Shan Ke
Published: November 2019

Sr0.97Ti0.6Fe0.4O3-δ (STF) and 8 mol% Y2O3 stabilized ZrO2 (YSZ) composites were prepared by mixing them in different weight fractions. The composites were compacted into discs, sintered and evaluated for phase stability, microstructure and mixed ionic-electronic conductivity. Phase analysis by XRD showed no clearly detectable secondary phases. Chemical analysis by energy dispersive spectroscopy (EDS) also showed the diffusion of elements (especially Y and Zr from YSZ). The electrical conductivity measurement on the STF-YSZ composites showed a decrease in total electrical and ionic conductivities with YSZ amount increasing. And the ionic conduction mechanism was concerned by impedance behavior analysis.
Effects of TiO2 Content on Microwave-Attenuating Properties of TiO2-Al2O3 Composite Ceramics
Authors: Wang Shiyuan , Zhang Yingchun
Published: November 2019

Microwave attenuation ceramic is a kind of dielectric loss material, which is used to absorb some unnecessary microwave electromagnetic field energy. For this attenuation material, it is required to have a large attenuation ratio, a sufficient mechanical strength and a good thermal stability. In this work, TiO2-Al2O3 composite ceramics were prepared via the conventional pressureless sintering method. The addition of CuO as liquid phase sintering aid was used to lower the sintering temperature of TiO2-Al2O3 composite ceramics. The effects of TiO2 content on sintering properties, phase composition, microstructure, mechanical properties and microwave-attenuating properties were investigated. With the increase of TiO2content, the sintering temperature decreased from 1300°C to 1100°C, meanwhile the dielectric constant rose from 15.42 to 23.80 and the dielectric loss increased from 0.042 to 0.314, which improved the attenuation of the TiO2-Al2O3 attenuation ceramics. When the content of TiO2 was 10 wt%, TiO2-Al2O3 composite attenuation ceramics with good properties could be obtained.
A study on Electrostrictive Properties of Ba2+, Bi3+, Eu3+ Doped PLZT (9/65/35) Transparent Ceramics
Authors: Chen Yijie , Zeng Xia , Cao Zhaodong , Ling Liang , Qiu Pingsun , He Xiyun , Sun Dazhi
Published: November 2019

Lead lanthanum zirconate titanate (PLZT 9/65/35) transparent ceramics, which modified with Ba2+, Bi3+, Eu3+ respectively, were prepared by hot-press sintering method. The phase structure, microstructure, ferroelectric, dielectric and electrostrictive properties of all the samples were examined and analysed. All of the ceramics show a pure perovskite phase and dense microstructure by the X-ray diffraction (XRD) and scanning electron microscope (SEM). Compared with undoped PLZT ceramics, the peak of the temperature-dependent of the dielectric constant curves with Ba2+ doped shift slightly to low temperature, meanwhile the Bi3+ and Eu3+ peak of the temperature-dependent dielectric constant curves decreases and broadens, which imply the relaxation of the as doped PLZT lattice. The hysteresis loops of Ba2+, Bi3+, Eu3+ doped PLZT show that a lower remanent polarization and coercive field. The field-induced strain hysteresis loops of all the sample were measured. The electrostrictive strain and hysteresis of Ba2+ and Eu3+ doped PLZT decrease monotonically. However, the electrostrictive strain of Bi3+ doped PLZT is increased. The experimental result implies that the A-site vacancies are induced by Ba2+, Bi3+ and Eu3+, which is in accordance with previous investigations. The strain curves of transparent materials exhibit low hysteresis under DC electric fields and this effect can be used in relative applications for great potential.
The Fabrication and Electrocaloric Effect of Bimodal-Grain Structure (Ba0.60Sr0.40)TiO3 Using the Induced Abnormal Grain Growth Method
Authors: Zhang H F , Chen X , Gao J , Lam K H , Liang S D , Fei L F , Mak C L , Chen J F
Published: November 2019

Bimodal-grain structure (Ba0.6Sr0.4)TiO3 ceramics had been prepared using induced abnormal grain growth method (IAGG). Two grain size distributions, between 10 ∼ 20 μm and 100 ∼ 300 μm, were found during the sintering temperature of 1250 ∼ 1350°C. Our results suggested that the ultra-large grain exhibited the high dielectric and ferroelectric properties comparable to the single crystal. At the same time, the fine-grain caused a phase diffusion transition at the Curie temperature about 20°C. The direct measured electrocaloric effect showed that the best performance is achieved with ΔT of 0.6 K, and ΔS of 1.02 J kg−1K−1 near room temperature and electric field strength of 2 MV/m.
Electrospray Preparation and Microwave Absorption Properties of ATO Hollow Micro/Nanospheres
Authors: Zhao Fang , Tang Xiangjun , Wang Xinkun , Zhang Sa , Duan Rongxia
Published: November 2019

Sb3+-doped SnO2 (ATO) hollow micro/nanospheres were prepared through electrospray and calcination technique. The influences of the calcination temperatures (500°C, 600°C, 700°C) on the crystal structure, micromorphology and microwave absorbing property of the calcined products were characterized by means of XRD, FT-IR, SEM and vector network analyzer. The results showed that Sb3+-doped SnCl2/PVP precursor polymer were smooth spheres with diameters of around 0.35-2.1μm. The pure rutile structure of SnO2 formed at 500°C, and the Sb3+ entered the lattice of SnO2. When the calcination temperature is 500°C and 600°C, ATO micro/nanospheres appeared to be hollow structure, and the surface were made up of many small particles. When the calcination temperature is 700°C, the ATO grains grown up which contained in the micro/nanospheres, and lost the sphere morphology and presented the irregular granlar forms. The microwave absorption properties of ATO hollow micro/nanospheres calcined at 600°C was the best as the matching thickness was 2mm. The minimum reflectivity can reach -32dB at 10.8GHz, and the frequency band with reflectivity less than -10dB was 9.8-12.2GHz. The minimum reflectivity of ATO hollow micro/nanospheres moved to a low frequency as the matching thickness increased. When the matching thickness was 3mm, the microwave absorption peaks were double, at which the frequency band with reflectivity less than -10dB was widen.
Preparation and Characterization of Gd and Zn Doped Apatite Lanthanum Silicate Electrolyte
Authors: Wu C S , Lei H , Huang J S , Yao D H , Cheng Y L , Huang Z L
Published: November 2019

Apatite lanthanum silicate is an oxygen ionic conductor with high conductivity. In this paper, research the effects of Gd and Zn double doping in La9.33Si6O26+x
. Synthesis La9.33Gd
x
Si5ZnO25+3x/2 (x = 0.2, 0.4, 0.6, 0.8) by Sol-gel Self combustion method, Characterization of the synthesized phase and electrical properties by X-ray diffraction, Scanning electron microscopy and Electrochemical workstations. The results show that doping can effectively improve the conductivity, La9.33Gd0.2Si5ZnO25.3has best conductivity that reach 1.49×10−3S/cm in 500°C.
Injection Molding Cycle Time Reduction for Automobile Headlamp Shell in Moldflow
Authors: Fouodji Cedric Tiomela , Xiao Hua Huang
Published: November 2019

In the injection molding cycle, the cooling time consumes more than 70% of the molding process, optimizing the molding cycle time can be done through the selection and the design of appropriate cooling system that will be able to achieve equal distribution of the temperature along the part and quickly dissipate the heat. This paper presents an analytic study on the simulation of cool + fill + pack + warp in Autodesk Moldflow 2012 for the automobile headlamp shell, the simulation is made on of four different cooling systems, after comparison of the obtained results, the Spiral Zigzag Conformal Cooling Channel (SZCC) has the lowest time required for the part to reach the ejection temperature, with 61.22 seconds, it also shows an improvement on the volumetric shrinkage with the part’s deflexion that have been reduced from 2.15 mm on the first design to 2.12 mm, making Spiral Zigzag Conformal cooling the best solution for this model.
Adaptive Force Control for Robotic Grinding of Complex Blades
Authors: Zhou Pokuang , Zhou Yuming , Xie Qianlong , Zhao Huan
Published: November 2019

Aiming at solving the robotic grinding problem of aircraft engine blades with complex surface, this paper proposed an adaptive force control method using fuzzy PID algorithm, which can ensure that blade surface is completely polished to eliminate residual texture and harmful stress concentration. First, an intelligent digital compliant grinder with active and passive compliance was developed. Second, a fuzzy PID adaptive algorithm was proposed, which can stabilize the contact force between the grinder and the blade. Third, a protection scheme was proposed to prevent excessive grinding. In the polishing process, the robot arm was fitted with the blade. According to the surface profile of the blade, the robot arm moved in a specific trajectory, keeping the blade in contact with the grinder. During grinding, some parameters, such as the abrasive belt velocity, the abrasive belt type and contact force, could affect the quality of the grinding process. Therefore, appropriate parameters were selected. The experimental results showed that the actual force fluctuates within 0.5N. In addition, the original surface roughness was 1.672um, which was reduced to 0.054um by adaptive force control method, comparing to 0.589 urn with the non-force control. Not only is the contact force more precisely controlled, but the grinding accuracy is greatly improved.
Fatigue Life Calculation of High-Power Disc Brake under Thermal-Mechanical Coupling
Authors: Zhang Shengfang , Han Zhiyu , Hao Qiang , Liu Yu , Sha Zhihua , Ma Fujian , Yang Dapeng
Published: November 2019

The fatigue failure mode of the brake disc is the initiation and expansion of the fatigue crack on the surface of the brake disc until the brake disc brakes. Therefore, considering the fatigue failure mode of the brake disc, the fatigue life of the brake disc is calculated. Firstly, the thermo-mechanical coupling model of the brake disc and pad is established by Abaqus software, so that temperature and stress of the brake disc could be obtained. Then, the surface crack initiation life of the brake disc is calculated by fe-safe software Finally, the fatigue crack growth life of the brake disc is calculated by nCode software. The calculation and analysis results show that the fatigue crack of the brake disc appears on the outer side of the brake disc friction surface under the working condition of this paper. The crack initiation life is that the number of braking is 12830 and the crack propagation life is 695000for the number of braking.
Design and Analysis of Vegetable Transplanter Based on Five-bar Mechanism
Authors: Sun Kai , Ge Rongyu , Li Taoyuan , Wang Jiatai
Published: November 2019

As one of the important components of automatic transplanter, duckbilled planting device, is a significant factor affecting the efficiency of the transplanter. Aiming at the problems of low transplanting rate, poor upright angle and poor stability of the transplanter, a five-pole transplanting mechanism is designed. Firstly, the parameters of the five-pole transplanting mechanism are analyzed and confirmed by MATALAB software. After virtual prototype model is established by SolidWorks software, simplified model is imported into ADAMS software for kinematics simulation, and then the trajectory, velocity and acceleration curve of the duckbilled tip are obtained. The simulation results verify the rationality of the structure and parameters and show that the trajectory of duckbilled planter meets the agronomic requirements of vegetable cultivation.
Research on Characteristics of Spacecraft Transport Dynamics Ambient Excitation Based on Conditions of Highway and Railway Transportation
Authors: Guangtong Liu , Xukai  , Guotao  , Qiang Zhang
Published: November 2019

Based on the highway and railway transportation conditions of several spacecraft from Beijing to launch site, the dynamics environment data acquisition scheme is designed. The response values of sensors before vibration reduction of transport packaging box are collected throughout the whole process. The power spectral density is obtained by filtering and Fourier transform, and the peak response frequency of the excitation source of spacecraft transportation environment is analyzed. It can be used as the basis for the design of vibration reduction system for spacecraft transportation, and some suggestions for the optimization design of vibration reduction system are put forward.
Investigation of Blocking Effect of Aviation High-Speed Towing Tank Based on CFD and EFD
Authors: Xiao Zhijian , Jiang Rong , Wu Bin , Wang Mingzhen , Yang Wenjing
Published: November 2019

Taking the unpowered model of a seaplane as the object, the blocking effect of aviation high-speed tank was studied by experimental and numerical methods in this paper. Firstly, the experiment of air field and drag were carried out in the bottom and front of the trailer. The experimental results of air field showed that the blocking effect of the air field was obvious in the bottom of trailer, while ignored in the front of trailer. The results of drag experiment under two conditions showed significant difference at mid-high speed, which proved the influence of blocking effect was obviouse. RANS method and overset grid were adopted in numerical simulation, and the accuracy of numerical method adopted in this paper was verified by comparing computed results of the model in the bottom of trailer with the experimental results. The computed results of hydrodynamic performance of the seaplane in finite and infinite domain showed that the influnence of the blocking effect of water could be nearly ignored, but the influnence of the blocking effect of air field was dominated. Finally, the hydrodynamic performance of the seaplane under the trailers with different sizes of chassis were carried out. The computed results showed that within the certain range, the degree of blocking effect of air field increased with the increase of geometrical variables of trailer chassis, further, which reached the maximum and kept constant when the variables exceeded a certain value.
Study on Axial Parameters of Stepped Ferrofluid Seals
Authors: Wang Guohong , Yang Xiaolong , Zhang Ruibo
Published: November 2019

As a new type of intelligent material seal technology, ferrofluid seal has been widely used in high speed, heavy load and large eccentricity occasions in recent years because of its long life, low leakage and high pressure resistance. Because of the limitation of the axial height of the axis, most of the existing studies are focused on the radial parameters, but the specific research on the axial parameters has not yet been carried out. In this study, the theoretical pressure capabilities of height of the distribution of axial teeth and axial slot width was calculated according to the theory of stepped ferrofluid seals by finite element method. And by changing the radial gap, the stepped ferrofluid seal is compared with the ordinary seal, and the calculation results are analysed and discussed. The results show that the distribution mode of the axial teeth has a great influence on the theoretical sealing pressure resistance. And the theoretical sealing pressure resistance reaches the maximum when the distribution mode is evenly distributed. The influence of the width of the axial slot on the theoretical sealing pressure resistance can be neglected, so the technological property and the design should be considered as far as possible. By comparing the stepped seal with the ordinary seal, the practicability of the stepped seal is further verified.
An End-to-End Named Entity Recognition Model for Chinese
Authors: Gong Cheng , Tang Jiuyang , Li Zhen
Published: November 2019

Named entity recognition is an important basic task in natural language processing. This paper proposes a named entity recognition method for end-to-end and efficient deep-loop neural networks. Using BERT to train sub-vectors as raw input enables the model to obtain more comprehensive text information, and at the same time, the BiLSTM network is focused on the attention mechanism, so that the network pays more attention to the key information in the text and ignores the redundant information to improve the recognition efficiency of the model. Finally, the relationship between any two tags is captured by the CRF layer, and the entire sentence is decoded and predicted. Experiments show that the method performs well on MSRA corpus.
Low-Temperature Compositions with Two Gel-forming Components for Water Shut-off Purposes and Oil Recovery Increase
Authors: Chernova U V , Kozlov V V , Altunina L K , Stasyeva L A , Kuvshinov V A , Sholidodov M R
Published: November 2019

This paper presents the results of laboratory studies on the developed low-temperature nanostructured gel-forming compositions for water shut-off purposes. Kinetic and rheological tests of different gel-forming compositions have been carried out. The physical model is devised, and filtration characteristics of the compositions are studied. Ultimately, the efficiency of their application to limit water inflow and to increase the oil displacement coefficient is investigated.
Structural and Mechanical Properties of Water Oil Emulsions of Highly Viscous Oils
Authors: Savrasova E A , Yudina N V , Nebogina N A , Volkova G I
Published: November 2019

The results of the study of the process of formation of emulsions in high viscosity oils are presented. The effect of the oil composition and the content of the aqueous phase on the microstructure, rheological properties, and activation energy of the viscous flow of oil-water emulsions are shown. Based on the analysis of the group composition of oils and the intermediate layer formed during the separation of emulsions, an increase in the mass fraction of benzene, alcohol-benzene resins, and asphaltenes in the intermediate layer is established.
Application of multilayer carbon nanotubes for creation of coatings absorbing electromagnetic radiation
Authors: Shchegolkov A , Zavolokina L , Diesperova N , Parfimovich I
Published: November 2019

The article presents the use of carbon nanotubes as modifiers-materials for protection against electromagnetic radiation. The technique of obtaining nanomodified composites, as well as the method of characterization of carbon nanostructures is presented. Studies have shown that there is a linear dependence of the reflection coefficient on the frequency for composites modified multilayer carbon nanotubes based on Ni / 0.16 MgO catalyst. It was found that composites containing multilayer carbon nanotubes based on Ni / 0.16 MgO allow to achieve low values of the reflection coefficient and non-dependence of the reflection coefficient on the increase in frequency.
Investigation of heating of nanomodified polymers under the action of microwave radiation
Authors: Shchegolkov A , Semenov A , Kiryakova M , Samofalova R
Published: November 2019

The article presents the study of heating nanomodified polymers under the action of microwave radiation. Modification of polyethylene was carried out using CNTs synthesized on Co-Mo / Al2O3-MgO catalysts. The influence of CNTs concentration on the temperature regime of polymer heating is investigated. The study of interaction with microwave radiation was carried out at the emitter power of 800 W in 2 minute increments for 8 minutes
Acoustic emission response and progressive failure behaviors of composite adhesively bonded joints loaded by Mode I and II
Authors: Liu Ran , Shen Gong-Tian , Zhang Peng-fei , Zhou Wei
Published: November 2019

The analysis of progressive failure process is one of the critical issues in the research of composite adhesive joints. In view of this point, acoustic emission (AE) is applied to real-time monitoring of the dynamic damage process of composite adhesive joints in some loading modes such as Mode I (double cantilever beam (DCB)) and Mode II (end notch flexures (ENF)). Furthermore, the high speed camera and scanning electron microscopy are carried to analyses the damage mechanisms of composite bonded joints. Results show that there are significant differences in the load- deflection curves of the specimens under the loads of Mode I and II. The main failure mode of the two types of loading modes is adhesion failure, and the accumulation of damage observed at the edge of the adhesively bonded layer cause defeat of the composite bonded joints. In addition, AE parameters including amplitude, hits, energy, and duration are connected with the fail mechanism. Furthermore, the dynamic characteristics of the AE signal, especially amplitude spectrum distribution, can provide evidences for studying progressive failure behaviors of composite adhesive joints.
The effect of geometry parameters on light harvesting performance of GaN nanostructure arrays—a numerical investigation and simulation
Authors: Zhangyang Xingyue , Liu Lei , Lv Zhisheng , Lu Feifei , Tian Jian
Published: November 2019

In this paper, COMSOL Multiphysics Commercial Package software is used to simulate the models of two kinds of GaN nanostructure arrays, and to study how the geometric structure and periodicity of arrays affect the optical properties of GaN nanostructures. By analyzing the schematic diagram of electric field distribution and absorption curves of GaN nanostructure arrays, we concluded that the absorptivity is a decreasing function of periodicity in non-homogenous shaped nanostructures. In addition, a gentle change in geometric structure or having a lower effective refraction index on the incident side of the light are more conducive to enhancing the light absorption ability of GaN nanostructure arrays. Simulation experiments on GaN nanostructures will provide some references for the structural design of photocathodes, which will help UV detectors to achieve efficient light absorption.
Uniqueness of minimal surfaces, Jacobi fields,and flat structures
Authors: Lee Hojoo
Published: November 2019

Combining two generically independent flat structures introduced by Chern and Ricci, we construct geometric harmonic functions on minimal surfaces. We show that various periodic minimal surfaces admit new uniqueness results in terms of our geometric harmonic functions. We prove a new rigidity theorem for associate families connecting the doubly periodic Scherk graphs and the singly periodic Scherk towers.
Subgaussianity is hereditarily determined
Authors: Dodos Pandelis , Tyros Konstantinos
Published: November 2019

Let

n
n

be a positive integer, let

X
=
(

X
1

,
…
,

X
n

)

\boldsymbol {X}=(X_1,\dots ,X_n)

be a random vector in

R

n

\mathbb {R}^n

with bounded entries, and let

(

θ
1

,
…
,

θ
n

)

(\theta _1,\dots ,\theta _n)

be a vector in

R

n

\mathbb {R}^n

. We show that the subgaussian behavior of the random variable

θ
1

X
1

+
⋯
+

θ
n

X
n

\theta _1 X_1+\dots +\theta _n X_n

is essentially determined by the subgaussian behavior of the random variables

∑

i
∈
H

θ
i

X
i

\sum _{i\in H} \theta _i X_i

where

H
H

is a random subset of

{
1
,
…
,
n
}

\{1,\dots ,n\}

.
Moduli space of metrics of nonnegative sectional or positive Ricci curvature on homotopy real projective spaces
Authors: Dessai Anand , González-Álvaro David
Published: November 2019

We show that the moduli space of metrics of nonnegative sectional curvature on every homotopy

R

P
5

\mathbb {R} P^5

has infinitely many path components. We also show that in each dimension

4
k
+
1

4k+1

there are at least

2

2
k

2^{2k}

homotopy

R

P

4
k
+
1

\mathbb {R} P^{4k+1}

’s of pairwise distinct oriented diffeomorphism type for which the moduli space of metrics of positive Ricci curvature has infinitely many path components. Examples of closed manifolds with finite fundamental group with these properties were known before only in dimensions

4
k
+
3
≥
7

4k+3\geq 7

.
Wide subcategories of 𝑑-cluster tilting subcategories
Authors: Herschend Martin , Jørgensen Peter , Vaso Laertis
Published: November 2019

A subcategory of an abelian category is wide if it is closed under sums, summands, kernels, cokernels, and extensions. Wide subcategories provide a significant interface between representation theory and combinatorics.

If

Φ
\Phi

is a finite dimensional algebra, then each functorially finite wide subcategory of

mod
⁡
(
Φ
)

\operatorname {mod}( \Phi )

is of the form

ϕ

∗

(

mod
⁡
(
Γ
)

)

\phi _{ {\textstyle *}}\big ( \operatorname {mod}( \Gamma ) \big )

in an essentially unique way, where

Γ
\Gamma

is a finite dimensional algebra and

Φ

⟶

ϕ

Γ

\Phi \stackrel { \phi }{ \longrightarrow } \Gamma

is an algebra epimorphism satisfying

Tor
1

Φ

⁡
(
Γ
,
Γ
)
=
0

\operatorname {Tor}^{ \Phi }_1( \Gamma ,\Gamma ) = 0

.

Let

F

⊆
mod
⁡
(
Φ
)

\mathscr {F} \subseteq \operatorname {mod}( \Phi )

be a

d
d

-cluster tilting subcategory as defined by Iyama. Then

F

\mathscr {F}

is a

d
d

-abelian category as defined by Jasso, and we call a subcategory of

F

\mathscr {F}

wide if it is closed under sums, summands,

d
d

-kernels,

d
d

-cokernels, and

d
d

-extensions. We generalise the above description of wide subcategories to this setting: Each functorially finite wide subcategory of

F

\mathscr {F}

is of the form

ϕ

∗

(

G

)

\phi _{ {\textstyle *}}( \mathscr {G} )

in an essentially unique way, where

Φ

⟶

ϕ

Γ

\Phi \stackrel { \phi }{ \longrightarrow } \Gamma

is an algebra epimorphism satisfying

Tor
d

Φ

⁡
(
Γ
,
Γ
)
=
0

\operatorname {Tor}^{ \Phi }_d( \Gamma ,\Gamma ) = 0

, and

G

⊆
mod
⁡
(
Γ
)

\mathscr {G} \subseteq \operatorname {mod}( \Gamma )

is a

d
d

-cluster tilting subcategory.

We illustrate the theory by computing the wide subcategories of some

d
d

-cluster tilting subcategories

F

⊆
mod
⁡
(
Φ
)

\mathscr {F} \subseteq \operatorname {mod}( \Phi )

over algebras of the form

Φ
=
k

A
m

/

(
rad

k

A
m

)

ℓ

\Phi = kA_m / (\operatorname {rad}\,kA_m )^{ \ell }

.
Corrigendum and addendum to “The structure monoid and algebra of a non-degenerate set-theoretic solution of the Yang–Baxter equation”
Authors: Jespers Eric , Kubat Łukasz , Van Antwerpen Arne
Published: November 2019

One of the main results stated in Theorem 4.4 of our article, which appears in Trans. Amer. Math. Soc. 372 (2019), no. 10, 7191–7223, is that the structure algebra

K
[
M
(
X
,
r
)
]

K[M(X,r)]

, over a field

K
K

, of a finite bijective left non-degenerate solution

(
X
,
r
)

(X,r)

of the Yang–Baxter equation is a module-finite central extension of a commutative affine subalgebra. This is proven by showing that the structure monoid

M
(
X
,
r
)

M(X,r)

is central-by-finite. This however is not true, even in case

(
X
,
r
)

(X,r)

is a (left and right) non-degenerate involutive solution. The proof contains a subtle mistake. However, it turns out that the monoid

M
(
X
,
r
)

M(X,r)

is abelian-by-finite and thus the conclusion that

K
[
M
(
X
,
r
)
]

K[M(X,r)]

is a module-finite normal extension of a commutative affine subalgebra remains valid. In particular,

K
[
M
(
X
,
r
)
]

K[M(X,r)]

is Noetherian and satisfies a polynomial identity. The aim of this paper is to give a proof of this result. In doing so, we also strengthen Lemma 5.3 (and its consequences, namely Lemma 5.4 and Proposition 5.5) showing that these results on the prime spectrum of the structure monoid hold even if the assumption that the solution

(
X
,
r
)

(X,r)

is square-free is omitted.
Assessing radiation dose limits for X-ray fluorescence microscopy analysis of plant specimens
Authors: Jones Michael W M , Kopittke Peter M , Casey Lachlan , Reinhardt Juliane , Blamey F Pax C , van der Ent Antony
Published: November 2019

Background and Aims

X-ray fluorescence microscopy (XFM) is a powerful technique to elucidate the distribution of elements within plants. However, accumulated radiation exposure during analysis can lead to structural damage and experimental artefacts including elemental redistribution. To date, acceptable dose limits have not been systematically established for hydrated plant specimens.

Methods

Here we systematically explore acceptable dose rate limits for investigating fresh sunflower (Helianthus annuus) leaf and root samples and investigate the time–dose damage in leaves attached to live plants.

Key Results

We find that dose limits in fresh roots and leaves are comparatively low (4.1 kGy), based on localized disintegration of structures and element-specific redistribution. In contrast, frozen-hydrated samples did not incur any apparent damage even at doses as high as 587 kGy. Furthermore, we find that for living plants subjected to XFM measurement in vivo and grown for a further 9 d before being reimaged with XFM, the leaves display elemental redistribution at doses as low as 0.9 kGy and they continue to develop bleaching and necrosis in the days after exposure.

Conclusions

The suggested radiation dose limits for studies using XFM to examine plants are important for the increasing number of plant scientists undertaking multidimensional measurements such as tomography and repeated imaging using XFM.