bluuebunny/crossref_metadata_2025_split huggingface dataset:
How close are shell models to the 3D Navier–Stokes equations?
Authors: Vincenzi Dario , Gibbon John D 
Published: July 2021

Abstract
Shell models have found wide application in the study of hydrodynamic turbulence because they are easily solved numerically even at very large Reynolds numbers. Although bereft of spatial variation, they accurately reproduce the main statistical properties of fully-developed homogeneous and isotropic turbulence. Moreover, they enjoy regularity properties which still remain open for the three-dimensional (3D) Navier–Stokes equations (NSEs). The goal of this study is to make a rigorous comparison between shell models and the NSEs. It turns out that only the estimate of the mean energy dissipation rate is the same in both systems. The estimates of the velocity and its higher-order derivatives display a weaker Reynolds number dependence for shell models than for the 3D NSEs. Indeed, the velocity-derivative estimates for shell models are found to be equivalent to those corresponding to a velocity gradient averaged version of the 3D Navier–Stokes equations (VGA-NSEs), while the velocity estimates are even milder. Numerical simulations over a wide range of Reynolds numbers confirm the estimates for shell models.
Nonlinear scalar field equation with competing nonlocal terms
*
Authors: d’Avenia Pietro , Mederski Jarosław , Pomponio Alessio 
Published: July 2021

Abstract
We find radial and nonradial solutions to the following nonlocal problem

−
Δ
u
+
ω
u
=

I

α

*

F

(

u

)

f

(

u

)

−

I

β

*

G

(

u

)

g

(

u

)

in

R

N

under general assumptions, in the spirit of Berestycki and Lions, imposed on f and g, where N ⩾ 3, 0 ⩽ β ⩽ α < N, ω ⩾ 0,

f
,
g
:
R
→
R

are continuous functions with corresponding primitives F, G, and I

α
, I

β
are the Riesz potentials. If β > 0, then we deal with two competing nonlocal terms modelling attractive and repulsive interaction potentials.
The nature of non-Gaussianity and statistical isotropy of the 408 MHz Haslam synchrotron map
Authors: Rahman Fazlu , Chingangbam Pravabati , Ghosh Tuhin 
Published: July 2021

Abstract
Accurate component separation of full-sky maps in the radio and microwave frequencies, such as the cosmic microwave background (CMB), relies on a thorough understanding of the statistical properties of the Galactic foreground emissions. Using scalar Minkowski functionals and their tensorial generalization known as Minkowski tensors, we analyze the statistical properties of one of the major foreground components, namely the Galactic synchrotron given by the full sky 408 MHz Haslam map. We focus on understanding the nature of non-Gaussianity and statistical isotropy of the cooler regions of the map as a function of angular scale. We find that the overall level of the non-Gaussian deviations does decrease as more high emission regions are masked and as we go down to smaller scales, in agreement with the results obtained in earlier works. However, they remain significantly high, of order 3.3σ, at the smallest angular scales relevant for the Haslam map. We carry out a detailed examination of the non-Gaussian nature using the generalized skewness and kurtosis cumulants that arise in the perturbative expansion of Minkowski functionals for weakly non-Gaussian fields. We find that the leading sources of non-Gaussianity are the kurtosis terms which are considerably larger than the skewness terms at all angular scales. Further, for the cooler regions of the Haslam map, we find that the non-Gaussian deviations of the Minkowski functionals can be well explained by the perturbative expansion up to second-order (up to kurtosis terms), with first-order terms being sub-dominant. Lastly, we test the statistical isotropy of the Haslam map and find that it becomes increasingly more isotropic at smaller scales.
Design of AC Load Analysis System Based on Single-chip Microcomputer
Authors: Zhang Chao , Li Yixin 
Published: July 2021

Abstract
A high-precision data sampling AC load analysis system is designed based on the core of ARM cortex M3 microcontroller named NXP LPC1500. The hardware composition, circuit design of each hardware part and the software design of the system are discussed in detail. The voltage, frequency, energy (W-h), harmonic current and current curve are also added into the analysis system. The circuit diagram of the functional part of the main circuit is provide, and the flow chart of the software design for the microcontroller are given. The experimental data show that the system works stably and reliably in actual application.
A Multi-sensor Data Fusion Algorithm Based on Unscented Kalman Filter for the Attitude Estimation of UAV
Authors: Wu Hongwei , Dou Yinke , Liu Jianlong 
Published: July 2021

Abstract
Aiming at the low accuracy of the inertial measurement unit and the error of the traditional attitude estimation algorithm, a UAV attitude estimation algorithm based on Unscented Kalman Filter (UKF) is proposed. The Euler angle method is used to describe the attitude algorithm model of the aircraft, and on this basis, the system state equation and observation equation of the UAV are established; the unscented Kalman filter algorithm is used to achieve the calculation of the attitude angle of the aircraft. By using APM flight control data, the simulation experiment is compared with the traditional attitude estimation algorithm. The experimental results show that the proposed algorithm has a great improvement in reliability and accuracy compared with the attitude estimation algorithm using extended Kalman filter (EKF).
Simulation Study on the Influence of Single Balance Shaft Mechanism on Noise Radiation of 3-Cylinder Engine
Authors: Wang Shangxue , Zhang Zhijun , Wang Yunfei 
Published: July 2021

Abstract
In this paper, simulation work was conducted to evaluate the vibration and noise of a 3-cylinder diesel engine. The finite element model of the whole engine and the dynamic model of the crankshaft system were established respectively. The boundary element method and the modal-based acoustic transfer vector (MATV) method were used to calculate the acoustic and vibration response, and the characteristic points were selected to monitor the radiated noise in the external acoustic field. Finally, through the structural optimization of the diesel engine model, the influence of adding a single balance shaft on the sound radiation of the whole machine was analyzed. The research results of this paper will provide technical support for the design of shock absorption and noise reduction of 3-cylinder engine in the application of unmanned ground vehicles (UGV), outboard engine, Unmanned Aerial Vehicles (UVA) and hybrid power system.
Motion simulation of a tensegrity snake-like robot based on the serpenoid curve
Authors: Wang Yihang , Zhang Xiaoshi , Li Xin , He Jingfeng 
Published: July 2021

Abstract
Due to their good motion performance, snake-like robots have been widely studied and researched for years and still have a lot of research interest. In this paper, we propose a snake-like robot based on tensegrity structure. Our snake-like robot is driven with cables on both sides, which is different from the serial structure snake-like robots driving by the motor at the axis of rotation. In order to verify the feasibility of the snake-like robot motion, we studied its inverse kinematics and performed simulation based on the serpenoid curve.
Research Progress on Surface Corrosion of Uranium Materials
Authors: Ming-ao Qin , Tao Wang , Chen Xie , Si-hao Tao 
Published: July 2021

Abstract
In order to understand the oxidation and corrosion mechanism of uranium and its compounds surface and explore the environmental system that can effectively alleviate the oxidation and corrosion of uranium materials, this paper reviews the research on the surface chemistry of uranium and its compounds at home and abroad, the adsorption behaviors of reactive gases such as H2, O2, CO, CO2 and inert gases such as N2 on different surfaces of uranium and its compounds were compared and analyzed, which deepens the understanding of the corrosion behavior of uranium and its compounds in the air, and gets some useful conclusions; this paper concludes that the interaction between U and various gases is accompanied by the transfer of charges, the main mechanism of action is that the different hybrid orbitals of gas atoms and U7s, U6d, U5f and other hybrid orbitals interact to form new chemical bonds, which led to related reactions and phenomena; in this paper, the research on surface corrosion of uranium and its compounds is also prospected from three aspects: improving the research methods, carrying out the study of different surface adsorption behaviors of different phases of uranium atoms, and exploring new systems for protecting uranium materials from oxidation and corrosion.
Influences of Temperature Field on Microstructural Characteristics of Laser Cladding Al2O3-13wt.%TiO2 Coating Prepared by Plasma Spraying
Authors: Wang Dongsheng , Zhang Yichi , Qu Guang , Zhou Xinhua 
Published: July 2021

Abstract
To explore effects of temperature field in laser cladding on structure of ceramic coating prepared by plasma spraying, a finite element model of continuous moving three-dimensional temperature field of laser cladded Al2O3-13wt.%TiO2 coating prepared by plasma spraying was constructed by the parametric design language of ANSYS finite element software to analyze temperature field during laser cladding. According to analysis results, it is very difficult to realize complete remelting of the whole preset ceramic coating during laser cladding when it is thick, which is related with the relatively low thermal conductivity of the ceramic materials. The whole coating can be divided into remelting zone, sintering zone and residual plasma spraying zone according to temperature field distribution in the zone of cladding. Given the optimal technological parameters, relatively thick remelting zone and sintering zone could be gained under the relatively low laser cladding power and relatively low scanning speed. Experimental results demonstrated that the ceramic coating after cladding formed remelting zone with small-sized and dense isometric crystals, sintering zone and lamellar residual plasma spraying zone. Moreover, the calculated results of thickness of the remelting zone and sintering zone conformed well to experimental values. This proved that the constructed finite element model is accurate and reliable.
Axial Stiffness Analysis of Double-Nut Ball Screw Pair
Authors: Zhu Yongjin , Jiang Shuyun 
Published: July 2021

Abstract
Based on the Hertz contact theory and considering changes in lead angle and contact angle, the axial stiffness model of a double-nut screw ball pair is established. A ball screw pair is taken as a calculation example, the accuracy of the theoretical model is verified. And the influence of the lead angle and the initial contact angle on the axial stiffness is analyzed. The research results show that the influence of the lead angle on the stiffness can be ignored and appropriately increasing the initial contact angle can effectively improve the stiffness performance.
Effect of Aging on the Toughness of Heat-Resistant 22Cr-15Ni-4Cu Austenitic Steel
Authors: Che Pengcheng , Wang Shuo , Cheng Yi , Wei Limin , Li Xianshuang , Xu Hang 
Published: July 2021

Abstract
As the 630°C USC power units develops rapidly, the two commonly employed austenitic steels HR3C and Super304H cannot be suitable with higher temperature and pressure any more. Due to their poor steam oxidation resistance and low strength, a new Austenitic heat-resistant steel 22Cr-15Ni-4Cu has been developed according to the strengthening mechanism of multiphase. The samples were aged for different times from 50h to 5000h under 650°C. The results show that the Charpy impact energy sharply decreases in the first 500h, and then maintains steady when aging time extends to 5000h further. Though both σ phase and M23C6 precipitated along the boundary, the sharply change of toughness was attributed to the M23C6 phase precipitation but not the σ phase. As the σ phase nearly started to precipitate after the ductile-brittle transition process. Due to the hard, large and low-plasticity M23C6 phase, it is difficult for the particles to harmonize with the matrix, which makes the composite matrix sensitive to initiation and propagation of cracks during the deformation process and then leads to the sharp decline of toughness of the steel.
Parameter decomposition model of three-wheel bootstrap high-pressure water-separated system
Authors: Haoran Sun , Chengyun Wu , Xiang Shen , Zhongdi Duan 
Published: July 2021

Abstract
The three-wheel bootstrap high-pressure water-separated system (HPWS) has been widely applied for the aircraft air-conditioner pack due to the advantages of high efficiency and stability. To guide the design of HPWS, a parameter decomposition model is established, including the sub-models of wet air, air cycle machine, heat exchanger and water extractor, and a tailor-made solution algorithm is proposed. The model accuracy is validated by the test data of an aircraft, and deviations of the calculated temperatures and pressures are within ± 5°C and ± 5%, respectively.
Effect of coupling agent content on properties of fly ash filled acrylic coating
Authors: Xuan YE , Shaojun Chen , Zhongbin Zhang 
Published: July 2021

Abstract
Fly ash was modified with 0wt%, 1wt%, 2wt%, 3wt% and 4wt% silane coupling agent. Modified fly ash was mixed with acrylic emulsion and additives to prepare acrylic coating. Coating adhesion, cup drawing experiment and heat insulation test were conducted. Results show that, with the increase of the content of coupling agent, the adhesion and toughness of the coating decrease. And the coating modified with 4wt% silane coupling agent has the best thermal insulation properties.
Structure and function of antagonistic pneumatic flexible rotary joint
Authors: Xia Wang , Dexu Geng , Lizhong Zhang , Wenzhi XU , Pei Wang 
Published: July 2021

Abstract
In order to solve the defects of the flexibility, adaptability and the safety of human-computer interaction of the arm joint of the service robot, an antagonistic rotary joint with buffer capability was developed by using the self-developed rotary driver. It consists of two groups of arc-shaped pneumatic artificial muscle drivers and the middle pneumatic brake with 180 degrees difference in the same installation phase, in order to avoid interference between the two groups of drivers, the two groups of pneumatic artificial muscle drivers are pre injected with 0.12Mpa air pressure, and the joint rotation function is realized based on the antagonistic principle, and the joint position and posture maintenance function is realized by the cooperation of pneumatic brake. The experimental results show that by controlling the gas pressure of the actuator, the rotation direction and the output driving force of the joint can be adjusted accurately; the rotation angle and output torque of the joint are proportional to the pressure difference between the two actuators. When the two actuators are filled with the same air pressure, the joint angle is 0 °, the rotation torque is 0; when the pressure difference between the two actuators is 0.24Mpa, the maximum joint angle is 60.5 °, the maximum rotation torque is 4.76N.m.
Microstructure and Mechanical Property of High Strength and High Toughness Titanium Alloy by Laser Deposition Manufacturing
Authors: Liu ZiXuan , Wang Chao , Yi JunZhen , Yu YongFu , Yu BoRong , Yang Guang 
Published: July 2021

Abstract
In this study, the high strength and high toughness Ti-6Al-3Mo-2Sn-2Zr-2Cr alloy was fabricated by the laser deposition manufacturing (LDM) technology. The effect of process parameters on the forming quality of LDMed alloy was studied. The microstructure and mechanical properties of LDMed Ti-6Al-3Mo-2Sn-2Zr-2Cr alloy was deeply analysed by the optical microscope, scanning electron microscope, tensile tester and impact tester. The results show that the optimized process parameters are as follows: laser power is 2.4 kW, scanning speed is 10 mm/s and scanning interval is 2.4 mm. Due to the temperature gradient, the LDMed titanium alloy shows obvious microstructure anisotropy exhibiting fine β equiaxed grain in scanning direction (XY direction), but shows coarse β columnar grain in deposition direction (Z direction). The micro-morphology exhibits classic dual-phase microstructure with basket appearance composing of equally distributed α phase and metastable β-transformed phase. Due to the grain boundary strengthening effect, obvious mechanical anisotropy can also be observed in LDMed titanium alloy showing a higher tensile strength, lower plasticity and impact toughness in XY direction, but reverses in Z direction.
Study on the preparation of new biomass fuel based on fungus chaff of Auricularia auricula
Authors: Zuo Huimin , Zhang Peng , Liu Ao , Zhou Mingyuan 
Published: July 2021

Abstract
After saturated steam pretreatment and thermo-pressure drying, the moisture content decreased and the calorific value increased, thus the waste fungus chaff was transformed into new biomass energy. The physicochemical properties of the fungus chaff after thermo-pressure drying were tested to meet the standard of being used as biomass fuel. The experiment showed that: The thermo-pressure drying technology can stably reduce the moisture content of the fungus bran from more than 55% to less than 35%, and increase the received base calorific value from 4763.9kJ/kg to 12213.8kJ/kg, which meets the requirements of biomass power plants. The performance of volatiles, slagging property and other related fuels is improved, which lays an experimental foundation for the industrial implementation of biomass fuel.
Study on Flame Retardant of Environmentally Friendly HDPE Sheath Material
Authors: Yan-hui Zhong , Zhi-wen Qiu , Zi-hao Chen , Ya-lan Long 
Published: July 2021

Abstract
Magnesium stearate was used to modify the surface of aluminum hydroxide, and a composite system composed of magnesium stearate and red phosphorus was used to study the flame retardancy of HDPE sheath. By testing the oxygen index, impact strength, bending strength, melt flow rate and hardness of the composite, the results show that aluminum hydroxide and red phosphorus can play a synergistic effect of flame retardancy. With the increase of aluminum hydroxide content, when the content of aluminum hydroxide is 60 phr, the flame retardancy of the composite can reach UL94 V2 level, and the bending strength and hardness will also be improved, but the impact strength and melt flow rate decreased.
Effect of curing time on properties of polyether MDI polyurethane elastomer
Authors: Gang LU , Chang-geng Shuai , Xue Yang 
Published: July 2021

Abstract
In order to study the effect of curing time on the properties of polyurethane elastomers in MDI system and provide guidance for the production of polyurethane elastomers in this system, the effects of gradient (6-12h) curing time on the thermal stability and mechanical properties of polyurethane elastomers in polyether MDI system were studied in this paper. The results showed that the properties of polyurethane improved with the extension of curing time, and the mechanical properties of polyurethane tended to be stable when the curing time exceeded 10h.
Effects of Back-Reflectors on a-Si: H Solar Cells
Authors: Hu Zhihua , Aierken Abuduwayiti , Diao Hongwei 
Published: July 2021

Abstract
ZAO (ZnO: Al)/Al and ITO/Ag complex back-reflectors were successfully applied to substrate nip and superstrate pin amorphous silicon solar cells respectively. As a result, the short circuit current (Isc) for a cell with a complex back-reflector increases significantly as compared with a cell without a complex back-reflector. For a superstrate pin cell prepared on SnO2 coated glass, the short-circuit current even increases up to 30%.
Microstructure and Wear Resistance of Ni-Al2O3 Nano-composite Coating
Authors: Qu Guang , Wang Dongsheng , Wang Qunyou , Hua Mengzhang 
Published: July 2021

Abstract
Ni-Al2O3 nano-composite coating was prepared on the ASP30 powder metallurgical steel surface for semiconductor encapsulation mould by using electrodeposition method. Effects of Al2O3 contents on microstructure, microhardness and wear resistance of composite coating were analyzed. Results demonstrate that due to refined crystalline strengthening, dispersion strengthening and high-density dislocation strengthening of Al2O3 nanoparticles in uniform distribution, Ni-Al2O3 nano-composite coating has more compact structure and smaller grain size compared to the pure Ni coating, which are conducive to increase microhardness and wear resistance of the coating significantly. Neither too low nor too high Al2O3 contents is beneficial to improve microhardness and wear resistance of composite coating. The pure Ni coating has serious adhesion wearing, while the nano-composite coating with the moderate Al2O3 content has the best performance and it mainly has mild abrasive wear, accompanied with some adhesion wearing. Relatively serious adhesion wearing occurs on the wear surface of pure Ni coating. Differently, wearing surface of Ni-Al2O3 nano-composite coating is mainly dominated by mild abrasive wear, accompanied with some adhesion wearing. Neither too low and too high Al2O3 content is conducive to improve microhardness and wear resistance of composite coating.
Effects of Nb and Mo content on mechanical properties of Ti-Nb-Mo-Ta alloys by two-step pressure-free and hot isostatic pressing sintering
Authors: Li Huicong , Cai Qi , Liu Jinxu , Feng Xinya , Li Shukui 
Published: July 2021

Abstract
The Ti-(15-30) Nb-(2-11) Mo-3.5Ta (wt.%) alloys with the composition interval of 5.0 wt.% for Nb and 3.0 wt.% for Mo were prepared by a two-step sintering method from blended elemental powders. After pressure-free sintering and hot isostatic pressing, fully dense Ti-Nb-Mo-Ta alloys with favourable compressive properties were obtained, rendering the alloys suitable to be used as structural or biomedical materials. The phase constituent, microstructure, and compressive properties were investigated for these Ti-Nb-Mo-Ta alloys. With the increasing Nb or Mo content, the volume fraction of the α phase and the grain size of the β phase decreased. The yield strength of the Ti-Nb-Mo-Ta alloys first declined and then increased with the increase of Nb or Mo content. As for the strain at failure, it increased monotonously for the Ti-xNb-8Mo- 3.5Ta alloys with the addition of Nb, and it first increased and then decreased for the Ti-25Nb-yMo-3.5Ta alloys with the addition of Mo. After analysing and comparing the variation trend of volume fraction of α phase, grain size, yield strength and strain at failure, the dominant strengthening mechanisms of the Ti-xNb-yMo-3.5Ta alloys were interpreted. The dominating mechanism was second-phase strengthening for the alloys with lower alloying elements content, and it changed to solid solution strengthening with the increase of alloying elements content.
Measurement and Analysis of sliding bearing vibration
Authors: Kongxing Ding , Faxin Zhu , Qijiang Yang , Xianbin Teng , Junwei Zhang , Wenxiang Chen , Zhaojian Wang 
Published: July 2021

Abstract
In this paper, by changing the loading of sliding bearing and the analysis software of LMS_TEST. LAB modal tester, the vibration characteristics of sliding bearing are studied by using the cantilever sliding bearing test platform, and the experimental results are studied and analyzed. It is very important to study the vibration problem of the sliding bearing. The vibration test data of the sliding bearing under different rotating speeds are analyzed to control the vibration within the allowable range.