bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of CMM Dynamic Measurement Error Based on Decision Regression Tree
Authors: Wu Xiaoping , Zhang Mei , Li Guihua , Zhao Haifeng , Wu Haiting
Published: August 2020

The best way to improve the accuracy of coordinate measuring machine (CMM) is to establish a correlation dynamic error correction model. However, due to the complex source of dynamic measurement error, the traditional method cannot work well. In this paper, decision regression tree is used to analyze the complex relationship between dynamic measurement error and its influencing factors, and the measurement error is predicted. The results show that the algorithm is simple, fast and superior to the least square estimation.
Research on Multi-Order Anti-Aliasing Filter in Bearing Profile Detection
Authors: Gaoqing He , Jiang Han , Leilei Liang , Jian Xiao
Published: August 2020

In the process of bearing profile detection, an analog displacement sensor is used, but there is noise interference in the process of data acquisition. In order to suppress noise interference, the paper designs three-order and fifth-order anti-aliasing filters according to the actual interference signal source. The resistance value and capacitance value are calculated according to the transfer function. The real object is made by the porous simulation board. The comparison between the input and output signals shows that the fifth-order anti-aliasing filter is better than the third-order anti-aliasing filter. Experiments show that the higher order anti-aliasing filter has a certain suppression effect on the noise signal, but the effect is not obvious. The signal distortion would happen and the system would become more and more complicated. For this reason, the fifth-order anti-aliasing filter is finally selected, and the actual sampling is completed, and the effect reaches the requirements of the detection system.
Application of 3D printing technology in equipment structure teaching
Authors: Xiaotao Bai , Jie Li
Published: August 2020

Aiming at the characteristics and current situation of equipment construction teaching, with the help of 3D printing technology, the production, assembly and demonstration of typical equipment model of equipment can be realized, and the teaching effect of equipment construction course can be significantly improved through specific application. At the same time, it puts forward reasonable suggestions for the popularization and application of 3D printing technology in teaching, and provides a reference for the reform of equipment structure teaching.
Experimental Research on The Distribution Law and Formation Reasons of As-cast Magnesium Alloy Laser Welding Porosity
Authors: Shen Yan-Jin , Zhou Jing , Liu Qian , Wu Fangrong
Published: August 2020

Characteristics and distribution of the weld porosity are observed by using OM and SEM after as-cast magnesium alloy AZ91D is welded by CO2 laser. And then the formation model of two types of porosity is established by use of organization composition and distribution of metal base. Besides, the mechanism of pores in welding is explained on three aspects including microscopic porosity, macroscopic porosity and escape of bubbles. Based on these models and mechanisms, the shape characteristics and distribution of a welding porosity in a welding seam is explained and the formula of bubbles escape is also given. In addition, the measures to prevent welding porosity are discussed preliminarily. And based on the preliminary research on this topic, when (0.2%Ca+0.4%Y) is added to AZ910D magnesium alloy and high strain rolling is used, the laser weld porosity ratio of magnesium alloy can be effectively reduced.
Research on the Combustion Performance of Mixed Charge of the Super-porous Coated Propellant
Authors: Xiang Cao , Lina Zhang , Ping Du , Shuai Jiang , Fengqiang Nan
Published: August 2020

In order to study the constant volume combustion performance of the mixed charge of super-porous propellant and super-porous coated propellant, 37-hole nitroguanidine propellant and 37-hole nitroguanidine coated propellant containing flame retardant TiO2 were prepared. At high temperature(50°C), normal temperature(20°C), low temperature(-40°C), a constant volume combustion experiment was performed on a mixed charge with a mass ratio of 1: 1 for the 37-hole propellant and the 37-hole coated propellant. The research results show that the constant volume combustion performance of the mixed charge is different from a single coated propellant and a single base propellant. The p-t, dp/dt-t and L-B curves of the mixed charge were between the coated propellant and the base propellant, but mixed charge has the greatest progressive combustion. And the temperature dependence of the progressive combustion of mixed charge is small, which has a certain low temperature effect.
Crack Growth Analysis of Rail Transit Steel Bridge Components Based on Damage Tolerance
Authors: Jia Yuanping , Cai Guoqiang , Sun Ruizhi , Li Qiang , Yang Chen
Published: August 2020

In recent years, the accidents caused by the instability and failure of the steel structure of the bridge occur frequently. Therefore, the research on high-performance steel members is one of the key directions of the development of Engineering Technology in the 21st century. In this paper, the damage tolerance evaluation method based on the finite element calculation of crack growth is used to analyze the fatigue of the load-bearing carbon fiber suspender with cracks in the operation stage, to correctly evaluate the remaining life and the remaining safety of the component, and to effectively handle Grasp the status and disease development of the bridge, so we can take timely and targeted measures to ensure the safety of the bridge.
Research on the Optimization of Process Parameters of the Current-Assisted Flow Spinning for 30CrMnSiA Cup-Shaped Part with Different Thickness
Authors: Can Chen , Lei Wang , Xiao Xu , Qinxiang Xia
Published: August 2020

A multi-pass current-assisted flow spinning experiment was carried out for the cup-shaped part with different thicknesses. The thickness deviation At, straightness u, and roundness e of the spinning parts were selected as the evaluation indexes of forming quality, and the effects of process parameters such as current intensity, preheating time, feed ratio and thinning rate on the forming quality were studied. Based on the genetic algorithm and BP neural network (GA-BP) model, the quality prediction model for the current-assisted flow spinning process was established, and the forming process was optimized by the genetic algorithm (GA). The verification test results are close to the predicted values of the model, in which the maximum error between the predicted value and the test result is about 6%. The results show that the proposed method is useful for the optimization of the current-assisted forming flow spinning process.
High-temperature tensile behavior of 3D SiC/SiC composites
Authors: Zhang Yu , Jiang Yun , Ren Duqiang , Zhang Qiang , Wang Xiaodong
Published: August 2020

The high-temperature tensile properties and stress-strain behavior of a 3D SiC/SiC composites prepared by the PIP method were investigated. Based on the FESEM analysis of the fracture morphology, the tensile failure mechanism of the composite at elevated temperature was discussed. The results show that the tensile strength of SiC/SiC composites showed a significant decline for specimens from a room temperature value of 482.5 MPa, to 167 MPa and 138 MPa at 1100 °C and 1300 °C, respectively. The toughening mechanism of composites at 1100 °C, including interface debonding, long pull-out fibers, and fracture mirror characteristics, is consistent with the pseudo-plastic fracture behavior implicated in the stress-strain curve. As a result of more significant oxidation, the fracture morphology of the specimen tested at 1300 °C was characterized by the signs including fiber-to-fiber bonding, larger size glassy phase, and shorter fiber pull-out length.
Study on the influence of post-treatment conditions on the internal stress of polystyrene products
Authors: Jin-wei Chen , Ling Yang , Li-xuan Wu , Da-hua Chen , Qun-shan Mai , Qiu-xian Weng , Xiang Liang , Shi-xin Su , Qi-qi Zhang
Published: August 2020

The polymer products in daily use generally have internal stress, and the uneven or excessive distribution of internal stress will cause warpage or stress cracking, which will affect the normal use of products. Using the heat treatment method of metal annealing to reduce its internal stress for reference, the polymer products were placed in the drying oven and water bath pot for post-treatment, and the influence of different post-treatment process parameters on the internal stress of polystyrene products represented by the mobile phone lens products was studied by using the self-developed molecular material transparent products internal stress detection device. The results showed that increasing the post-treatment temperature below the hot deformation temperature can effectively reduce the internal stress and improve the internal stress distribution of polystyrene products at the same post-treatment time under different post-treatment temperatures and slow cooling conditions, and there was an optimal post-treatment temperature of 60 Centigrade;the polystyrene products after post-treatment had the secondary internal stress under the rapid cooling conditions, so that the internal stress distribution of products was worse than that of polystyrene products without post-treatment. The experimental results can lay a theoretical and practical foundation for seeking effective measures to reduce the internal stress of polymer products in the future.
A Comparative Study of Selective Laser Melting Processed Inconel 625 Superalloy: Fatigue Performances under Constant Amplitude Loading and Single Tensile Overload
Authors: Ren D Q , Jiang Y , Zhang Y , Hu X A
Published: August 2020

The Inconel 625 used in this study was fabricated by the selective laser melting technology. The fatigue properties of this alloy were investigated at room temperature. The compact-tension specimens were used to study the fatigue crack growth behaviors under stress ratio R = 0.1, and overload ratio ROL = 1.4. Three typical behaviors of overload fatigue crack growth (increase, drop and increase) were studied.
Application of polyaspartic acid derivative in circulating cooling water system with high concentration multiple
Authors: Gao Y H , Li H H , Zheng Y X , Zhang L H , Liu Z F
Published: August 2020

The polyaspartic acid derivative compound was applicated in circulating cooling water system with high concentration multiple with the water quality of circulating cooling water system was characterized by higher hardness, higher alkalinity and higher corrosive ion content in order to solve the problem of scale and corrosion of the circulating cooling water system. The formulation of the polyaspartic acid derivative compound was determined to be PASP-AESA-ASP, ZnSO4, HPAA and BTA with the mass ratio of 15:4:6:0.1. The polyaspartic acid derivative compound had a good protective effect on A3 carbon steel in high-concentration-salt water and good biodegradability.
Experimental Investigation on Face Grinding of 2024AI/SiCp with Electroplated Diamond Wheel
Authors: Shaolei Wang , Shuzheng Shi , Jiuqiang Wang , Xin Li , Zhanying Wang , Chunhua Zhu
Published: August 2020

SiCw / 2024Al composite has excellent physical and chemical properties, such as high specific strength, good wear resistance, low coefficient of thermal expansion, etc. It has been widely used in the development of modern science and technology. An experimental research on face grinding of SiC particle-reinforced aluminium matrix composite 2024Al/SiCp with electroplated diamond grinding wheel was carried out. The effects of different grinding parameters on the surface morphology, grinding force and grinding quality of workpiece are analyzed. The results show that high quality ground surface can be achieved by using this technology; the residual stress on machined surface is compressive stress; grinding parameters have little effects on tangential and normal grinding forces, but have stronger effect on axial grinding force than that in other two directions, and the axial grinding force increased notablely as the increasing of grinding depth.
Expermental Research on Light-curing Rapid Prototyping Silicon Oxide Ceramics
Authors: Yan Liang , Yuan WenJing , Yan Biao
Published: August 2020

3D printing technology is an emerging technology that is rapidly developing in the manufacturing field. It can easily and automatically manufacture complex three-dimensional shapes that are difficult to be produced by various processing methods. Printable ceramic materials are prepared by mixing photosensitive resin and different ceramic powders. By studying the effects of dispersant, slurry, PH value, silica particle size and solid phase content on slurry viscosity and fluidity, low viscosity Ceramic slurry with high solid phase content and good fluidity. The effects of different solid phase contents on the bending strength, firing shrinkage, porosity and density of ceramics were tested. The results show that the bending strength of sintered SiO2 ceramics reaches 15.78Mpa at a solid content of 70vol %. The density was 76.21%, porosity was 40.04%, sintering shrinkage was 0.89%.
Effect of inclusion defect on fatigue failure of FGH96 superalloy at 600°C
Authors: Miao Guolei , Sun Tong , Wang Xiaodong
Published: August 2020

High cycle fatigue experiments were conducted at 600°C to study the effect of manufacture defect on crack initiation behaviour of FGH96. The experiments were performed at different stress levels to considering the coupling effect of loading and defect. The stress ratio was selected at 0.05. The results revealed that the fatigue life behaviour are much different in different loading levels. In order to examine the crack initiation mechanism, Scanning electron microscopy (SEM) method was used to analyze the failure surfaces. Different failure modes including surface cracking, sub surface cracking as well as internal crack initiation were found. The tested fatigue lives were found to have a strong relation with the mode of the crack initiation.
Study on dielectric barrier discharge in nanostructured electrode materials
Authors: Zhang Dongpeng
Published: August 2020

In order to conduct dielectric barrier discharge experiments under normal pressure and low voltage (less than 15000V), an ac high-voltage differential power supply based on series-parallel LCC-type(Inductor L and capacitor Cr, Cp are connected in series and parallel structure) resonant converter is designed. The designed power supply prototype has the advantages of small size, light weight and easy operation. The power supply prototype has been tested on loads for many times. Its output repeatability is good and it can continuously output stable sinusoidal ac voltage. At the same time, the prototype also has a strong ability to resist electromagnetic interference. Moreover, the dielectric barrier discharge experiment is carried out using copper electrode with zinc oxide nanowires and copper electrode without zinc oxide nanowires. The experimental results show that the starting voltage of the test group with nanostructures growing on the surface is smaller, about 2500V lower than that of the latter under the same dielectric conditions and discharge spacing. In terms of the discharge phenomenon, the former has a better discharge process consistency, the non-nanostructured electrode discharge is unstable, and the difference in the discharge process is obvious.
Melting behavior of PET with sulfonated polypropylene wax
Authors: Xin Ming-liang , Yin Xiang-Bin , Da Jing , Li Mao-dong , Li Hua , Wu Wen-dong
Published: August 2020

The effects of sulfonate group and composition of sulfonateionomer (SPSN) with low molecular mass on the morphologies, non-isothermal crystallization and melting behaviors of poly(ethylene terephthalate) (PET) in PET/SPSN blends are investigated by thermogravimetric analysis (TG). Sulfonateionomer (SPSN) is synthesized from polypropylene wax by two steps, and at 300°C the mass loss of SPSN is only 1wt % with a good thermal stability. The result shows that sulfonateionomer could is an effective nucleating agent.
Study on dynamic mechanical properties of viscoelastic damping materials based on finite element theory
Authors: Guo Tie-neng , Yang Tao , Gu Yun-chao
Published: August 2020

The relationship between the vibration parameters and the dynamic mechanical properties of the rubber material is established through the vibration reduction experiment and the finite element theory of the ZN-35 silicon rubber damper, which provides a new method for the prediction of the wide-band dynamic mechanical properties of the viscoelastic damping material.
The effect of antioxidant 1010 on the thermo-oxidative aging properties of polycarbonate/acrylonitrile–butadiene–styrene blends
Authors: Zhu Z F , Wen J , Zhang Q , Yuan S , Yin L
Published: August 2020

In this research, the thermo-oxidative aging properties of PC/ABS with different content of antioxidant 1010 were studied. The ΔE value of the sample with 1wt% antioxidant 1010 was 35.3% lower than that without antioxidant before and after 500h aging. After aging for 500h, the elongation at break and impact strength of samples with 1wt% antioxidant 1010 decreased by about 76% and 42% respectively, which were 8% and 5% higher than those without antioxidant. The results of ATR-FTIR spectrum shown that antioxidant 1010 reduced the degradation of rubber phase (PB) in ABS caused by thermo-oxidative aging.
Experimental Study on the Dry Shrinkage Properties of Nano Concrete Materials
Authors: Li Wei , Wang Xiao-chu , Xiong Long , Huang Zhen
Published: August 2020

This paper focuses on the effect of adding nano-CaCO3 and nano-SiO2 to concrete with different dosages on its shrinkage performance, studies have shown that: nano materials on the drying shrinkage of concrete will produce certain negative effect, make the drying shrinkage of concrete increases, so need through the selection of the aggregate, the optimization of mixture ratio and effective maintenance means to reduce the drying shrinkage of concrete, such as the nano materials minimizes the negative effect on the drying shrinkage of concrete; In this paper, the effects of two kinds of nano materials on concrete properties are comprehensively compared. The results show that the improvement of mechanical properties and durability of concrete by NS is slightly better than that of NC under the appropriate dosage, but the selling price of NC is much lower than that of NS. Besides, the fluidity of concrete after adding NC is better than that of concrete mixed with NS, and the drying shrinkage rate of concrete at each age is lower.
Experimental Study on Mechanical Properties of Nano Concrete Materials
Authors: Li Wei , Wang Xiao-chu , Xiong Long , Huang Zhen
Published: August 2020

This paper focuses on the influence of nano-CaCO3 and nano-SiO2 materials on the mechanical properties of concrete mixed with different dosages. Through the compressive strength and flexural strength tests of nano concrete, the flexural and compression ratio of each sample are calculated, and the influence of nano materials on the flexural and compression ratio of concrete is analyzed. It is proved that nanometer materials with very small particle size and large surface area have excellent properties that ordinary materials do not possess. It can be used as admixture of concrete to improve the mechanical properties and durability of concrete.
Evaluating the anti-corrosion behavior of hybrid zirconium-polyethyleneimine layer by mean of electrochemical method
Authors: Yang R , Xu P Y , Jing Y , Xin G
Published: August 2020

Zirconia conversion coating as an eco-friendly treatment technology is the most promising method of replacing traditional phosphating technology. A new kind of zirconia/polyethyleneimine composite coating was fabricated on carbon steel. Potentiodynamic polarization, electrochemical impedance spectroscopy and salt spray test analyses were used to evaluate the corrosion behavior of samples in 3.5wt% NaCl solution. Scanning electron microscope was used to characterize the surface morphology of the samples. Results showed that zirconia coating after polyethyleneimine (PEI) treatment generated a protective layer through combination of physisorption and chemisorption, which enabled the new composite coating to perform much better than single zirconia coating. The zirconium-polyethyleneimine layer demonstrated the best anti-corrosion performance with the lowest corrosion current and highest polarization resistance. Overall, this study established a promising anticorrosion method involving the production of zirconia coating as an interlayer prior to forming PEI coating on a substrate.
Influence of steel pipe on mechanical properties of airport cement concrete pavement
Authors: Lai Y , Ma D X , Wang P , Liu Y , Su J X , Xiang H L , Liu C L
Published: August 2020

This paper studies the influence of steel pipe on mechanical properties of airport cement concrete pavement. The flexural and compressive strength of concrete are analysed when different steel pipes are added into ordinary concrete. It is shown that the flexural and compressive strength of ordinary concrete are higher than those of concrete containing steel pipe at the age of 7 and 28 days. The compressive strength of concrete decreases more than the flexural strength when the steel pipe is added into concrete. The flexural strength of concrete containing Φ32 seamless steel pipe, DN32 welded steel pipe and DN40 welded steel pipe can still meet the mechanical properties of airport concrete. Compared with DN32 welded steel pipe and DN40 welded steel pipe, the selection of Φ32 seamless steel pipe is beneficial to the mechanical properties of concrete.
Hot compression constitutive equation of Mg-5Sm-2Y alloy
Authors: Qing Zhang , Haining Wang , Ying Wang , Ping Li
Published: August 2020

The hot compression tests were carried out at deformation temperatures ranging from 300 to 450°C and strain rates ranging from 0.01 to 1 s−1, and the hot deformation behavior and constitutive equation of Mg-5Sm-2Y magnesium alloy was investigated. The results showed that the flow stress of the alloy is affected greatly by deformation temperature and strain rate during the hot compression deformation. The flow stress of the alloy decreases with the increase of deformation temperature at the same strain rate, and decreases with the decrease of strain rate at the same deformation temperature. The constitutive equation for hot compression flow stress of the alloy is established in a hyperbolic-sine form. In the equation, the stress index n is 7, and the hot deformation activation energy Q is 212 kJ/mol.
Electrochemical properties study on NCM622 by in suit modification of Mg and F
Authors: He Rui , Bai Xue , Wei Aijia , Zhang Lihui , Liu Zhenfa
Published: August 2020

With the rapid development of portable electronic products and electric cars, higher requirements are put forward for the performance of high energy density lithium ion battery. Nickel-rich layered metal oxides with higher energy density and lower raw material cost are considered as ideal cathode materials for lithium ion batteries. However, the structural defects and unstable interfacial chemical properties make the electrochemical properties degrade and reduce the safety of the material. Based on the previous work, this project synthesized NCM622 materials by solid phase method, and studied the influence of F, Mg and MgF2 on the comprehensive electrochemical properties of NCM622 materials. The relationship between microstructure and electrochemical properties of the materials was studied..
Investigation of milling stability based on a cutting force segmentation model
Authors: Jin G , Liu H , Zhang XY , Sun GX
Published: August 2020

The chatter vibration is the major limiting factor for higher metal removal rates in milling process. This paper proposed an integral model of cutting force with helical cutter considering the sectional characteristics of cutting force. Based on the model, the variation law of the upper and lower limit angles of the cutting process under different radial cutting depths is analysed. The results show that the shape of cutting force for each tooth has a characteristic of three sections. Moreover, the process dynamic equation of thin-walled parts cutting is constructed based on the model. And, the stability lobe diagram is obtained by semi-discretization method. The time-domain simulations are carried out in different cutting parameters around the stable island to verify the correctness of the prediction method. The results show that the method has good ability to predict the cutting stability of cutters with helix angle.
Self-lubricating and Antifriction Characteristics of Three-dimensional Co-continuous Network Graphite / Cast Steel Composites
Authors: Chunyi ZHAN , Shengshan FENG , Weifeng WU , Qingqing BIAN , Jianli CHEN , Dong HUANG , Zebin WEI , Dabao LI , Zehui CHEN , Jincheng ZENG , Shuixin TAN , Guancheng LI
Published: August 2020

The infiltration casting method is used for the preparation of three-dimensional co-continuous network graphite / cast steel composite material in atmospheric pressure. The friction and abrasion behavior of composite specimen in condition of dry sliding friction are investigated by peg-tray friction abrasion tester. The anti-wear mechanism of composite material is discussed. The results show that the relative wear resistance of the composite material is 6.5～7.1 times of graphitic cast iron, and average friction coefficient is 60.5～73.3% of graphitic cast iron. The composite material provides with good self-lubricating and anti-friction property in condition of dry sliding friction.
Liquid crystal block copolymer micelles with aggregation-induced emission from corona chains
Authors: Wang Siyu , Luo Yunjun , Li Xiaoyu
Published: August 2020

Aggregation-induced emission (AIE) is a very useful tool to study the self-assembly process of block copolymers. However, most of the studies have been focused on the AIE process of the micelle core block. In this study, a typical AIEgen tetraphenylethylene (TPE) was introduced into the corona-forming block of the liquid crystal diblock copolymer. Although the coronal chains were still soluble in solution and the TPE group content was very low, due to the highly crowded and stretched chains, there was significant fluorescence emission after micellization. This provides a new research direction for the AIE process of diblock polymers and is of great significance for the study of the star micelle models.
The potential use of fish collagen as a new functional materials due to its good immune-compatibility
Authors: Liu Chao , Sun Jiao
Published: August 2020

As a marine-derived biological macromolecule, fish collagen is attracting more and more attention for its potential application in the biomedical field. Currently, there is no systematic evaluation of immuno-compatibility of fish collagen in vivo. In the present study, 200 mg/kg hydrolyzed tilapia fish collagen (HTC) was injected subcutaneously into mice for 21 consecutive days. To evaluate the effects of HTC on spleen lymphocytes proliferation, cell counting assay (CCK-8) was performed. Flow cytometry was applied to study the effect of HTC on the apoptosis of spleen lymphocytes. Mouse serum immunoglobulin G (IgG) and immunoglobulin M (IgM) were determined by Enzyme-linked immunosorbent assay (ELISA). The results showed no significant difference for the proliferation and apoptosis of spleen lymphocytes between the HTC group and the control group (subcutaneously injected with 0.9% NaCl for 21 consecutive days). And there was no significant difference for serum IgG and IgM levels between the control group and HTC group. The above results showed that the hydrolyzed tilapia fish collagen possesses good immune-compatibility, which can potentially be used as biocompatible implanted biomaterials in vivo.
Sb2MoO6 Decorated on Graphene as an Anode Material for Lithium/Sodium-Ion Batteries
Authors: Wu Q , Wang H G
Published: August 2020

The ternary materials have attracted wide attention owing to the synergistic effect and multi-component flexibility. Herein, Sb2MoOe decorated on graphene (Sb2MoO6/RGO) is synthesized and proved to be a novel anode material for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). Benefitting from the conductive networks of graphene and the synergistic effect between two metal elements, Sb2MoO6/RGO shows the improved the electrochemical performance, including a high reversible capacity of 967.2 mAh g−1 for LIBs and 349.4 mAh g−1 for SIBs at 100 mA g−1, an excellent cycle performance of 606.8 mAh g−1 for LIBs after 55 cycles and 264.9 mAh g−1 for SIBs after 100 cycles at 100 mA g−1. Therefore, Sb2MoO6/RGO has a wide application prospect for both the LIBs and SIBs.
The Effect of Cr2O3+Al Addition on the Microstructure of Combustion Electrode Joint
Authors: Shen Chao , Li Zhizun , Sun Liming , Han Fengqi
Published: August 2020

During manual self propagating welding, there are segregation phenomena of iron rich phase and copper rich phase. Cr element can restrain the segregation phenomenon of iron rich phase and copper rich phase. Cr is a strong ferrite element. When the amount of Cr2O3 + Al in the flux is less than 3wt%, with the increase of &2O3 + Al content, the microstructure of the weld alloy tends to be homogenized and the mechanical properties of the welded joint improve; when the amount of Cr2O3 + Al in the flux is more than 4wt%, Cr and C form Carbides are easy to produce microcracks in the fusion zone and reduce the mechanical properties of the joint. The best addition of Cr2O3 + Al in the flux is 3wt% ~ 4wt%.
Can the law of maximum entropy production describe the field-induced orientation of ellipsoids of rotation?
Authors: Gimsa Jan
Published: August 2020

Electrostatic approaches are successful in explaining the experimentally observed field-induced orientations of the axis with the highest Clausius-Mossotti factor. For conductive or nonconductive, prolate or oblate spheroids, this is always the longest axis when different frequency-dependent dispersions of their effective conductivity along the three principal axes are neglected. Here, it is shown that these orientations correspond to the ‘law of maximum entropy production’ (LMEP) by comparing the axes-ratio dependencies of the torques calculated with the electrostatic approach with the effective conductivity differences between a suspension with field-oriented and randomly oriented objects. At low volume fraction, the obtained conductivity differences, which enter the LMEP, predict almost exactly the torque curves when plotted over axis ratio of the objects. Since the field-induced orientation at constant field strength increases the effective conductivity, the suspension system obviously does not behave according to the Prigogine principle, which would demand the minimization of energy dissipation and entropy production through object orientation. However, the Prigogine principle requires the suspension system to be close to equilibrium in its linear range. These conditions must be rejected if the LMEP is to be applied. Apparently the LMEP provides a phenomenological criterion for axis orientation, even though it is not yet clear whether and how increased conductivity, power dissipation and entropy production can also be introduced as driving forces at the single object level. However, the results also indicate that the disregard of energy dissipation may not be a problem in the electrostatic description of field-induced object orientation.
Extending holomorphic forms from the regular locus of a complex space to a resolution of singularities
Authors: Kebekus Stefan , Schnell Christian
Published: August 2020

We investigate under what conditions holomorphic forms defined on the regular locus of a reduced complex space extend to holomorphic (or logarithmic) forms on a resolution of singularities. We give a simple necessary and sufficient condition for this, whose proof relies on the Decomposition Theorem and Saito’s theory of mixed Hodge modules. We use it to generalize the theorem of Greb-Kebekus-Kovács-Peternell to complex spaces with rational singularities, and to prove the existence of a functorial pull-back for reflexive differentials on such spaces. We also use our methods to settle the “local vanishing conjecture” proposed by Mustaţă, Olano, and Popa.
Some remarks on strong approximation and applications to homogeneous spaces of linear algebraic groups
Authors: Balestrieri Francesca
Published: August 2020

Let

k
k

be a number field and

X
X

a smooth, geometrically integral quasi-projective variety over

k
k

. For any linear algebraic group

G
G

over

k
k

and any

G
G

-torsor

g
:
Z
→
X

g: Z \to X

, we observe that if the étale-Brauer obstruction is the only one for strong approximation off a finite set of places

S
S

for all twists of

Z
Z

by elements in

H^1_{\text {\'{e}t}}(k,G), then the étale-Brauer obstruction is the only one for strong approximation off a finite set of places

S
S

for

X
X

. As an application, we show that any homogeneous space of the form

G

/

H

G/H

with

G
G

a connected linear algebraic group over

k
k

satisfies strong approximation off the infinite places with étale-Brauer obstruction, under some compactness assumptions when

k
k

is totally real. We also prove more refined strong approximation results for homogeneous spaces of the form

G

/

H

G/H

with

G
G

semisimple simply connected and

H
H

finite, using the theory of torsors and descent.
Automatic real analyticity and a regal proof of a commutative multivariate Löwner theorem
Authors: Pascoe J. , Tully-Doyle Ryan
Published: August 2020

We adapt the “royal road” method used to simplify automatic analyticity theorems in noncommutative function theory to several complex variables. We show that certain families of functions must be real analytic if they have certain nice properties on one-dimensional slices. Let

E
⊂

R

d

E \subset \mathbb {R}^d

be open. A function

f
:
E
→

R

f:E \to \mathbb {R}

is matrix monotone lite if

f
(

φ
1

(
t
)
,
…
,

φ
d

(
t
)
)

f(\varphi _1(t), \ldots , \varphi _d(t))

is a matrix monotone function of

t
t

whenever

t
∈
(
0
,
1
)

t \in (0,1)

, the

φ
i

\varphi _i

are automorphisms of the upper half plane, and the tuple

(

φ
1

(
t
)
,
…
,

φ
d

(
t
)
)

(\varphi _1(t), \ldots , \varphi _d(t))

maps

(
0
,
1
)

(0,1)

into

E
E

. We use the “royal road" to show that a function is matrix monotone lite if and only if it analytically continues to the multivariate upper half plane as a map into the upper half plane. Moreover, matrix monotone lite functions in two variables are locally matrix monotone in the sense of Agler-McCarthy-Young.
Sequences of monoidal transformations of a regular noetherian local domain
Authors: Granja A.
Published: August 2020

Let

R
R

be a regular noetherian local ring of dimension

d
≥
2

d\geq 2

. We characterize the sequences

(

R
i

)

i
≥
0

(R_i)_{i\geq 0}

of successive monoidal transforms of

R
=

R
0

R=R_0

such that

S
=

⋃

i
≥
0

R
i

S =\bigcup _{i\geq 0} R_i

is a valuation ring. This characterization involves two well-known conditions in the case of quadratic transforms (

(

R
i

)

i
≥
0

(R_i)_{i\geq 0}

either switches strongly infinitely often or is height one directed), to which we must add the condition that a family of ideals of

S
S

(finitely supported on the exceptional divisors along the sequence) is linearly ordered by inclusion. Moreover and under the assumption that

S
S

is a valuation ring, we compute the limit points (in the Zariski–Riemann space over the quotient field of

R
R

equipped with the patch topology) of the valuation rings associated with the order valuations defined by the centers of the monoidal transforms as well as the limit points of the valuation rings associated with the order valuations defined by the maximal ideals of the rings

R
i

R_i

,

i
≥
0

i\geq 0

.
Left-orderability, branched covers and double twist knots
Authors: Turner Hannah
Published: August 2020

For some families of two-bridge knots, including double twist knots with genus at least four, we determine precisely the set of integers

n
>
1

n>1

such that the fundamental group of the

n
n

-fold cyclic branched cover of the 3-sphere along these knots is left-orderable. There are knots, including the figure-eight knot, for which this set is empty. We give the first class of hyperbolic knots, not of this type, for which these integers can be completely determined.
On the existence of Ulrich vector bundles on some irregular surfaces
Authors: Lopez Angelo
Published: August 2020

We establish the existence of rank two Ulrich vector bundles on surfaces that are either of maximal Albanese dimension or with irregularity

1
1

, under many embeddings. In particular, we get the first known examples of Ulrich vector bundles on irregular surfaces of general type. Another consequence is that every surface such that either

q
≤
1

q \le 1

or

q
≥
2

q \ge 2

and its minimal model has rank one, carries a simple rank two Ulrich vector bundle.
On the geometry of the second fundamental form of the Torelli map
Authors: Frediani Paola , Pirola Gian
Published: August 2020

In this paper we give a geometric interpretation of the second fundamental form of the period map of curves and we use it to improve the upper bounds on the dimension of a totally geodesic subvariety

Y
Y

of

A

g

\mathsf {A}_g

generically contained in the Torelli locus obtained by Elisabetta Colombo, Paola Frediani, and Alessandro Ghigi [Internat. J. Math. 26 (2015), no. 1, 1550005] and A. Ghigi, P. Pirola, and S. Torelli (to appear on Communications in Contemporary Mathematics, https:// doi.org/10.1142/S0219199720500200). We get

dim
⁡
Y
≤
2
g
−
1

\dim Y \leq 2g-1

if

g
g

is even,

dim
⁡
Y
≤
2
g

\dim Y \leq 2g

if

g
g

is odd. We also study totally geodesic subvarieties

Z
Z

of

A

g

\mathsf {A}_g

generically contained in the hyperelliptic Torelli locus and we show that

dim
⁡
Z
≤
g
+
1

\dim Z \leq g+1

.
A note on mean convex 𝜆-surfaces in ℝ³
Authors: Guang Qiang
Published: August 2020

Inspired by the work of Spruck and Xiao on mean convex translators, in this note, we show that any closed and mean convex

λ
\lambda

-surface in

R

3

\mathbb {R}^3

with

λ
≤
0

\lambda \leq 0

must be convex. We also give a curvature estimate for mean convex

λ
\lambda

-surfaces in

R

3

\mathbb {R}^3

.
A universal gap for non-spin quantum control systems
Authors: Gauthier Jean-Paul , Rossi Francesco
Published: August 2020

We prove the existence of a universal gap for minimum time controllability of finite dimensional quantum systems, except for some basic representations of spin groups.

This is equivalent to the existence of a gap in the diameter of orbit spaces of the corresponding compact connected Lie group unitary actions on the Hermitian spheres.
Pollard waves with underlying currents
Authors: Henry David , Lyons Tony
Published: August 2020

We construct an exact solution of the geophysical fluid dynamics governing equations which models waves in the presence of underlying currents, extending Pollard’s wave solution to admit underlying meridional and vertical currents at mid-latitudes. We show that these currents cannot be prescribed arbitrarily, but rather must be constant and form a velocity vector which is parallel to the Earth’s rotation vector. At the equator, there is freedom to prescribe a meridional current term which may vary both zonally and vertically.
COVID-19 antibody therapeutics tracker: a global online database of antibody therapeutics for the prevention and treatment of COVID-19
Authors: Yang Lifei , Liu Weihan , Yu Xin , Wu Meng , Reichert Janice M , Ho Mitchell
Published: August 2020

Facing the COVID-19 global healthcare crisis, scientists worldwide are collaborating to develop prophylactic and therapeutic interventions against the disease. Antibody therapeutics hold enormous promise for the treatment of COVID-19. In March 2020, the Chinese Antibody Society, in collaboration with The Antibody Society, initiated the “COVID-19 Antibody Therapeutics Tracker” (“Tracker”) (https://chineseantibody.org/covid-19-track/) program to track the antibody-based COVID-19 interventions in preclinical and clinical development globally. The data are collected from the public domain and verified by volunteers on an ongoing basis. Here, we present exploratory data analyses and visualization to demonstrate the latest trends of COVID-19 antibody development, based on data for over 150 research and development programs and molecules included in the “Tracker” as of 8 August 2020. We categorized the data mainly by their targets, formats, development status, developers and country of origin. Although details are limited in some cases, all of the anti-SARS-CoV-2 antibody candidates appear to target the viral spike protein (S protein), and most are full-length monoclonal antibodies. Most of the current COVID-19 antibody therapeutic candidates in clinical trials are repurposed drugs aimed at targets other than virus-specific proteins, while most of these virus-specific therapeutic antibodies are in discovery or preclinical studies. As of 8 August 2020, eight antibody candidates targeting the SARS-CoV-2 S protein have entered clinical studies, including LY-CoV555, REGN-COV2, JS016, TY027, CT-P59, BRII-196, BRII-198 and SCTA01. Ongoing clinical trials of SARS-CoV-2 neutralizing antibodies will help define the utility of these antibodies as a new class of therapeutics for treating COVID-19 and future coronavirus infections.
A native annual forb locally excludes a closely related introduced species that co-occurs in oak-savanna habitat remnants
Authors: Johnson Jens C , Williams Jennifer L
Published: August 2020

Despite the ubiquity of introduced species, their long-term impacts on native plant abundance and diversity remain poorly understood. Coexistence theory offers a tool for advancing this understanding by providing a framework to link short-term individual measurements with long-term population dynamics by directly quantifying the niche and average fitness differences between species. We observed that a pair of closely related and functionally similar annual plants with different origins—native Plectritis congesta and introduced Valerianella locusta—co-occur at the community scale but rarely at the local scale of direct interaction. To test whether niche and/or fitness differences preclude local-scale long-term coexistence, we parameterized models of competitor dynamics with results from a controlled outdoor pot experiment, where we manipulated densities of each species. To evaluate the hypothesis that niche and fitness differences exhibit environmental dependency, leading to community-scale coexistence despite local competitive exclusion, we replicated this experiment with a water availability treatment to determine if this key limiting resource alters the long-term prediction. Water availability impacted population vital rates and intensities of intraspecific versus interspecific competition between P. congesta and V. locusta. Despite environmental influence on competition our model predicts that native P. congesta competitively excludes introduced V. locusta in direct competition across water availability conditions because of an absence of stabilizing niche differences combined with a difference in average fitness, although this advantage weakens in drier conditions. Further, field data demonstrated that P. congesta densities have a negative effect on V. locusta seed prediction. We conclude that native P. congesta limits abundances of introduced V. locusta at the direct-interaction scale, and we posit that V. locusta may rely on spatially dependent coexistence mechanisms to maintain coexistence at the site scale. In quantifying this competitive outcome our study demonstrates mechanistically how a native species may limit the abundance of an introduced invader.
RabbitMash: accelerating hash-based genome analysis on modern multi-core architectures
Authors: Yin Zekun , Xu Xiaoming , Zhang Jinxiao , Wei Yanjie , Schmidt Bertil , Liu Weiguo
Published: August 2020

Motivation

Mash is a popular hash-based genome analysis toolkit with applications to important downstream analyses tasks such as clustering and assembly. However, Mash is currently not able to fully exploit the capabilities of modern multi-core architectures, which in turn leads to high runtimes for large-scale genomic datasets.

Results

We present RabbitMash, an efficient highly optimized implementation of Mash which can take full advantage of modern hardware including multi-threading, vectorization and fast I/O. We show that our approach achieves speedups of at least 1.3, 9.8, 8.5 and 4.4 compared to Mash for the operations sketch, dist, triangle and screen, respectively. Furthermore, RabbitMash is able to compute the all-versus-all distances of 100 321 genomes in <5 min on a 40-core workstation while Mash requires over 40 min.

Availability and implementation

RabbitMash is available at https://github.com/ZekunYin/RabbitMash.

Supplementary information

Supplementary data are available at Bioinformatics online.
Routine Laboratory Blood Tests Predict SARS-CoV-2 Infection Using Machine Learning
Authors: Yang He S , Hou Yu , Vasovic Ljiljana V , Steel Peter A D , Chadburn Amy , Racine-Brzostek Sabrina E , Velu Priya , Cushing Melissa M , Loda Massimo , Kaushal Rainu , Zhao Zhen , Wang Fei
Published: August 2020

Background

Accurate diagnostic strategies to identify SARS-CoV-2 positive individuals rapidly for management of patient care and protection of health care personnel are urgently needed. The predominant diagnostic test is viral RNA detection by RT-PCR from nasopharyngeal swabs specimens, however the results are not promptly obtainable in all patient care locations. Routine laboratory testing, in contrast, is readily available with a turn-around time (TAT) usually within 1-2 hours.

Method

We developed a machine learning model incorporating patient demographic features (age, sex, race) with 27 routine laboratory tests to predict an individual’s SARS-CoV-2 infection status. Laboratory testing results obtained within 2 days before the release of SARS-CoV-2 RT-PCR result were used to train a gradient boosting decision tree (GBDT) model from 3,356 SARS-CoV-2 RT-PCR tested patients (1,402 positive and 1,954 negative) evaluated at a metropolitan hospital.

Results

The model achieved an area under the receiver operating characteristic curve (AUC) of 0.854 (95% CI: 0.829-0.878). Application of this model to an independent patient dataset from a separate hospital resulted in a comparable AUC (0.838), validating the generalization of its use. Moreover, our model predicted initial SARS-CoV-2 RT-PCR positivity in 66% individuals whose RT-PCR result changed from negative to positive within 2 days.

Conclusion

This model employing routine laboratory test results offers opportunities for early and rapid identification of high-risk SARS-CoV-2 infected patients before their RT-PCR results are available. It may play an important role in assisting the identification of SARS-CoV-2 infected patients in areas where RT-PCR testing is not accessible due to financial or supply constraints.