Wear Mechanism of Cemented Carbide Tool in High Speed Milling of Stainless Steel

Adhesion of cutting tool and chip often occurs when machining stainless steels with cemented carbide tools. Wear mechanism of cemented carbide tool in high speed milling of stainless steel 0Cr13Ni4 Mo was studied in this work. Machining tests on high speed milling of 0Cr13Ni4 Mo with a cemented carbide tool are conducted. The cutting force and cutting temperature are measured. The wear pattern is recorded and analyzed by high?speed camera, scanning electron microscope(SEM) and energy dispersive X?ray spectroscopy(EDS). It is found that adhesive wear was the dominant wear pattern causing tool failure. The process and microcosmic mechanism of the tool’s adhesive wear are analyzed and discussed based on the experimental results. It is shown that adhesive wear of the tool occurs due to the wear of coating, the a nity of elements Fe and Co, and the grinding of workpiece materials to the tool material. The process of adhesive wear includes both microcosmic elements di usion and macroscopic cyclic process of adhe?sion, tearing and fracture.

Alkaline digestion behavior and alumina extraction from sodium aluminosilicate generated in pyrometallurgical process

In pyrometallurgical process, Al-and Si-bearing minerals in iron and aluminum ores are easily transformed into sodium aluminosilicates in the presence of Na_2O constituents, which alters the leaching behaviors of Al_2O_3 and SiO_2. It was confirmed that sodium aluminosilicates with different phase compositions synthesized at various roasting conditions were effectively digested in the alkaline digestion process. Under the optimum conditions at temperature of 100–120°C, liquid-to-solid ratio(L/S) of 10:2 mL/g, caustic ratio of 4, and Na_2O concentration of 240 g/L, the actual and relative digestion ratio of Al_2O_3 from the synthesized sodium aluminosilicates reached maximums of about 65% and 95%, respectively, while SiO_2 was barely leached out. To validate the superior digestion property of sodium aluminosilicate generated via an actual process, the Bayer digestion of an Al_2O_3-rich material derived from reductive roasting of bauxite and comprising Na_(1.75) Al_(1.75) Si_(0.25)O_4 was conducted; the relative digestion ratio of Al_2O_3 attained 90% at 200°C.

Visible-light-induced deoxygenative C2-sulfonylation of quinoline N-oxides with sulfinic acids for the synthesis of 2-sulfonylquinoline via radical reactions

A simple and efficient method for the synthesis of 2-sulfonylquinoline from deoxygenative C2-sulfonylation of quinoline N-oxides with sulfinic acid induced by visible light is presented.This protocol shows a broad substrate scope,and desired products with various substituents can be formed in moderate to high yields at room temperature.

Super-high bed sintering for iron ores: inhomogeneous phenomena and its mechanism during mineralizing

The inhomogeneous sinter properties in super-high bed sintering have been reported in our previous research.To inves-tigate the reasons for the inhomogeneous phenomena,detailed sampling and analysis of mixed material bed and sintered bed in super-high bed sintering plant were executed.The results indicated that the higher porosity and thinner dendrite of silico-ferrite of calcium and aluminum in the upper layer as well as dense structure and higher secondary hematite content in the lower layer led to the heterogeneities of mechanical strength and reduction properties exceeding 20%and 10%,respectively.From the bed top downward,the basicity of mixed material decreased from 2.13 to 1.68 because the average particle size increased from 2.65 to 4.56 mm.Fluxes and fuels gathered in finer particles(-3 mm)of mixed material,and the-3 mm particles of mixed material generated more liquid phase than+3 mm ones.The heat input of super-high sintering bed was inhomogeneous due to the heat accumulation effect and unreasonable fuel distribution.The inhomo-geneous sintering heat condition in sintering bed resulted in the different quantities and properties of liquid phase.The inhomogeneous quantities and properties of liquid phase that were influenced by inhomogeneous distribution of chemical composition,particle size,and heat input led to inhomogeneous mineralizing results.Homogeneous mineralizing condition is the key for homogeneous super-high bed sintering.

East Asian VLBI Network observations of active galactic nuclei jets:imaging with KaVA+Tianma+Nanshan

The East Asian Very Long Baseline Interferometry(VLBI) Network(EAVN) is a rapidly evolving international VLBI array that is currently promoted under joint efforts among China,Japan and Korea.EAVN aims at forming a joint VLBI Network by combining a large number of radio telescopes distributed over East Asian regions.After the combination of the Korean VLBI Network(KVN) and the VLBI Exploration of Radio Astrometry(VERA) into Ka VA,further expansion with the joint array in East Asia is actively promoted.Here we report the first imaging results(at 22 and 43 GHz) of bright radio sources obtained with Ka VA connected to Tianma 65-m and Nanshan 26-m Radio Telescopes in China.To test the EAVN imaging performance for different sources,we observed four active galactic nuclei(AGN) having different brightness and morphology.As a result,we confirmed that the Tianma 65-m Radio Telescope(TMRT) significantly enhances the overall array sensitivity,a factor of 4 improvement in baseline sensitivity and 2 in image dynamic range compared to the case of Ka VA only.The addition of the Nanshan 26-m Radio Telescope(NSRT) further doubled the east-west angular resolution.With the resulting high-dynamic-range,high-resolution images with EAVN(Ka VA+TMRT+NSRT),various fine-scale structures in our targets,such as the counter-jet in M87,a kink-like morphology of the 3 C 273 jet and the weak emission in other sources are successfully detected.This demonstrates the powerful capability of EAVN to study AGN jets and to achieve other science goals in general.Ongoing expansion of EAVN will further enhance the angular resolution,detection sensitivity and frequency coverage of the network.

A process model for BOF process based on bath mixing degree

The process model for BOF process can be applied to predict the liquid steel composition and bath temperature during the whole steelmaking process. On the basis of the traditional three-stage decarburization theory, the concept of mixing degree was put forward, which was used to indicate the effect of oxygen jet on decarburization. Furthermore, a more practical process model for BOF steelmaking was developed by analyzing the effect of silicon, manganese, oxygen injection rate, oxygen lance height, and bath temperature on decarburization. Process verification and end-point verification for the process model have been carried out, and the verification results show that the predic- tion accuracy of carbon content reaches 82.6% （the range of carbon content at the end-point is less than 0. 1wt%） and 85.7% （the range of carbon content at end-point is 0. 1wt% -0.7wt%） when the absolute error is less than 0.02wt% and 0.05wt%, respectively.

Features and mechanisms of self-sintering of molybdenite during oxidative roasting

Roasting experiments were carried out with pure reagents as raw materials.The self-sintering behaviors of molybdenite(MoS_(2))during oxidation were investigated by thermodynamic calculation,XRD,SEM-EDS and high-temperature in situ analysis.The results indicate that the desulfurization efficiency of MoS_(2) pellet decreases with the increase of roasting temperature from 600 to 700℃,owing to the expansion of sintered area.At the very beginning of roasting,sintered layer can be rapidly formed and cover the pellet surface on the windward side,and meanwhile,MoO_(2)and Mo_(4)O_(11) intensively appear and constitute the sintered layer together with MoO_(3).Moreover,it is proven that MoO_(3)-rich products containing low-valence molybdenum oxides have low melting points,thus easy to be melted during the occurrence of exothermic reaction between MoS_(2) and O_(2),which leads to the sintering of materials.

Comparison of reduction disintegration characteristics of TiO_2-rich burdens prepared with sintering process and composite agglomeration process

To reveal the impact of the composite agglomeration process（CAP） on the reduction disintegration properties of TiO_2-rich ironmaking burden for a blast furnace, the reduction disintegration indices（RDIs）, mineral constituents, and microstructure of the products prepared by the CAP and the traditional sintering process（TSP） were investigated. The results showed that, compared to the sinter with a basicity of 2.0 prepared by the TSP, the RDI_（＋6.3） and the RDI_（＋3.15） of the CAP product with the same basicity increased by 28.2wt% and 13.7wt%, respectively, whereas the RDI_（-0.5） decreased by 2.7wt%. The analysis of the mineral constituents and microstructure of the products indicated that the decreasing titanohematite content decreased the volume expansion during reduction. Meanwhile, the decreasing perovskite content decreased its detrimental effect on the reduction disintegration properties. In addition, the higher silicoferrite of calcium and aluminum（SFCA） content improved the strength of the CAP product. Together, these factors result in an improvement of the RDI of the CAP products. In addition, compared to the sinter, the reduced CAP products clearly contained fewer cracks, which also led to mitigation of reduction disintegration.

Targeted Search for Fast Radio Bursts with Nanshan 26m Radio Telescope

Fast radio bursts(FRBs)are radio transients that are bright and have short duration,with their physical mechanism not being fully understood.We conducted a targeted search for bursts from FRB 20201124A between 2021 June 2and July 20.High time-resolution data were collected for 104.5 hr using the ROACH2-based digital backend.We introduce the details of our FRB search pipeline which is based on HEIMDALL and FETCH.Testing of the injected mock FRBs search could help us better understand the performance of the pipelines,and improve the search algorithms and classifiers.To study the efficiency of our pipeline,5000 mock FRBs were injected into the data and searched using the pipeline.The results of the mock FRB search show that our pipeline can recover almost all(?90%)the injected mock FRBs above a signal-to-noise ratio(S/N)threshold of 15,and the performance is still acceptable(?80%)for injected S/Ns from 10 to 15.The recovery fraction displays relations with S/N,dispersion measure and pulse width.No bursts were detected from FRB 20201124A in the middle of 2021.The non-detection of FRB 20201124A may be due to its quiet phase window or no emission above the threshold of the Nanshan telescope.

Maternal weight,blood lipids,and the offspring weight trajectories during infancy and early childhood in twin pregnancies

Background The intrauterine environment has a profound and long-lasting influence on the health of the offspring.However,its impact on the postnatal catch-up growth of twin children remains unclarified.Therefore,this study aimed to explore the maternal factors in pregnancy associated with twin offspring growth.Methods This study included 3142 live twin children born to 1571 mothers from the Beijing Birth Cohort Study conducted from 2016 to 2021 in Beijing,China.Original and corrected weight-for-age standard deviation scores of the twin offspring from birth to 36 months of age were calculated according to the World Health Organization Child Growth Standards.The corresponding weight trajectories were identified by the latent trajectory model.Maternal factors in pregnancy associated with the weight trajectories of the twin offspring were examined after adjustment for potential confounders.Results Five weight trajectories of the twin children were identified,with 4.9%(154/3142)exhibiting insufficient catch-up growth,30.6%(961/3142),and 46.8%(1469/3142)showing adequate catch-up growth from different birth weights,and 15.0%(472/3142)and 2.7%(86/3142)showing various degrees of excessive catch-up growth.Maternal short stature[adjusted odds ratio(OR)=0.691,95%confidence interval(CI)=0.563–0.848,P=0.0004]and lower total gestational weight gain(GWG)(adjusted OR=0.774,95%CI=0.616–0.972,P=0.03)were associated with insufficient catch-up growth of the offspring.Maternal stature(adjusted OR=1.331,95%CI=1.168–1.518,P<0.001),higher pre-pregnancy body mass index(BMI)(adjusted OR=1.230,95%CI=1.090–1.387,P<0.001),total GWG(adjusted OR=1.207,95%CI=1.068–1.364,P=0.002),GWG rate(adjusted OR=1.165,95%CI=1.027–1.321,P=0.02),total cholesterol(TC)(adjusted OR=1.150,95%CI=1.018–1.300,P=0.03)and low-density lipoprotein-cholesterol(LDL-C)(adjusted OR=1.177,95%CI=1.041–1.330)in early pregnancy were associated with excessive growth of the offspring.The pattern of weight trajectories was similar between monochorionic and dichorionic twins.Maternal height,pre-pregnancy BMI,GWG,TC and LDL-C in early pregnancy were positively associated with excess growth in dichorionic twins,yet a similar association was observed only between maternal height and postnatal growth in monochorionic twins.Conclusion This study identified the effect of maternal stature,weight status,and blood lipid profiles during pregnancy on postnatal weight trajectories of the twin offspring,thereby providing a basis for twin pregnancy management to improve the long-term health of the offspring.

CA-DTS:A Distributed and Collaborative Task Scheduling Algorithm for Edge Computing Enabled Intelligent Road Network

Edge computing enabled Intelligent Road Network(EC-IRN)provides powerful and convenient computing services for vehicles and roadside sensing devices.The continuous emergence of transportation applications has caused a huge burden on roadside units(RSUs)equipped with edge servers in the Intelligent Road Network(IRN).Collaborative task scheduling among RSUs is an effective way to solve this problem.However,it is challenging to achieve collaborative scheduling among different RSUs in a completely decentralized environment.In this paper,we first model the interactions involved in task scheduling among distributed RSUs as a Markov game.Given that multi-agent deep reinforcement learning(MADRL)is a promising approach for the Markov game in decision optimization,we propose a collaborative task scheduling algorithm based on MADRL for EC-IRN,named CA-DTS,aiming to minimize the long-term average delay of tasks.To reduce the training costs caused by trial-and-error,CA-DTS specially designs a reward function and utilizes the distributed deployment and collective training architecture of counterfactual multi-agent policy gradient(COMA).To improve the stability of performance in large-scale environments,CA-DTS takes advantage of the action semantics network(ASN)to facilitate cooperation among multiple RSUs.The evaluation results of both the testbed and simulation demonstrate the effectiveness of our proposed algorithm.Compared with the baselines,CA-DTS can achieve convergence about 35%faster,and obtain average task delay that is lower by approximately 9.4%,9.8%,and 6.7%,in different scenarios with varying numbers of RSUs,service types,and task arrival rates,respectively.

Super-high bed sintering for iron ores:problems ascertainment

Super-high bed sintering process is an important development direction of iron ore sintering for its lower emission and higher yield.However,there is a lack of deep understanding of the uneven quality of super-high bed sintering products,and the deterioration of reduction disintegration performance,the thickening of hearth layer and the reduction in energy-saving effect are perplexing enterprises and researchers.To ascertain the problems of super-high bed sintering,ten sintering machines with the areas of 265,280,360,550 and 660 m^(2)and bed depth above 900 mm were sampled and analyzed.The results showed that problems were mainly shown in the unevenness of chemical composition,macrostructure,mechanical strength and metallurgical performance.The chemical composition exhibits severe segregation in both horizontal and vertical directions,with basicity segregation reaching as high as 0.81.The uneven macrostructure of sinter is reflected in a 10%difference in porosity and mechanical strength increase in 16%–19%along the vertical direction.The reducibility and reduction disintegration performance gradually deteriorate along the bed depth,with a difference of 10.5%in reducibility and 7.3%in RDI−0.5 mm(reduction disintegration index of sinter with size smaller than 0.5 mm).

Super-high bed sintering for iron ores:behaviors,causes and solutions of horizontal segregation on strand

Horizontal segregation has been a constraint to the development and application of super-high bed sintering.To eliminate the horizontal segregation of super-high bed sintering,several typical sintering machines were sampled and analyzed,and theoretical calculation was made to compare the bed depth and their differences in different areas within the mixture bin.Then,solutions were proposed and applied to a 265 m^(2) sintering machine.The results showed that the horizontal seg-regation of the 265 m^(2) sintering machine was dominated by particles larger than 8 mm with horizontal segregation degree of 0.48,while 360 and 550 m^(2) sintering machines were affected by 5-8 mm and 1-3 mm particles with horizontal segregation degree of 0.27 and 0.31,respectively.Causes analysis indicated the different segregation distribution results from the matching of the bed depth of each area within the mixture bin.Finally,the horizontal segregation degree not larger than 0.06 was achieved by optimizing the time parameters and the division of three zones on the 265 m^(2) sintering machine.

Visible-light induced cascade radical cyclization of sulfinic acids and o-(allyloxy)arylaldehydes towards functionalized chroman-4-ones

An efficient method for the synthesis of functionalized chroman-4-ones induced by visible light via the radical cyclization reaction of sulfinic acids and o-(allyloxy)arylaldehydes at room temperature was described.The corresponding products were isolated with moderate to good yields.Radical mechanism was proposed fo r this trans formation.Anti-microbial activity of some desired compounds we re screened.

An efficient method for iron ore sintering with high-bed layer:double-layer sintering

Poor permeability and low sintering productivity restrict the development of high-bed sintering.An efficient method of the double-layer sintering process(DLSP)was proposed to achieve high-bed sintering and solve the aforementioned problems.Theoretical calculation and sintering pot experiments were implemented to investigate the double-layer sintering process.Traditional sintering process and DLSP were compared in terms of sintering indices,metallurgical properties and morphology characterization.Under the condition of traditional sintering process,DLSP successfully realized fast velocity and highly productive sintering of 1000-mm high bed.After the sintering bed is charged and ignited twice,the air permeability of the bed has been greatly improved.Sintering time is shortened significantly by simultaneous sintering of the upper and lower feed layers.Under the condition of bed height proportion of 350/650 mm and pre-sintering time of 20 min,the yield,tumbler strength,productivity and solid fuel consumption are 69.96%,65.87%,1.71 t(m^(2)h)^(-1)and 56.71 kg/t,respectively.Magnetite,hematite,calcium ferrite and complex calcium ferrite are the main phases of DLSP products.The metallurgical properties of DSLP products meet the requirement of ironmaking.It indicates that DLSP is an effective method to solve the disadvantages of bad permeability and low sintering productivity in high-bed sintering.

Preparation of blast furnace burdens by composite agglomeration process: effect of distribution of magnetite and hematite concentrates in pelletized and matrix feed

Effect of distribution of iron concentrates between pelletized and matrix feed on the preparation of blast furnace burdens from two different kinds of fine iron concentrates (magnetite and hematite) by composite agglomeration process (CAP) was explored. It was found that when the mass ratio of iron concentrate A (magnetite) to iron concentrate B (hematite) in the mixed feed was constant, the proportion of iron concentrate A in the pelletized and matrix feed significantly affected the quality of CAP products. Particularly, as the proportion of iron concentrate A in the pelletized feed increased from 0 to 100%, the yield decreased from 82.11% to 79.19% and the tumbler index decreased from 71.33% to 68.27%. The mineralization characterization results indicated that when 100% iron concentrate A was used as the pelletized feed, the crystallization styles of the outer layer and the inner layer of the pellet were different, and a lot of pores exist around hematite and magnetite phases in the pelletized part, with the weak connection of pelletized and matrix part, resulting in poor strength of agglomeration product.