The identification of rock mass hazard sources is fundamental for preventing rockfall and landslide disasters in mountainous regions,with rock mass structural characteristics playing a vital role in hazard assessment....The identification of rock mass hazard sources is fundamental for preventing rockfall and landslide disasters in mountainous regions,with rock mass structural characteristics playing a vital role in hazard assessment.In this study,terrestrial laser scanning(TLS)and unmanned aerial vehicle(UAV)technologies were integrated to enhance the evaluation methodology for rock mass hazard sources,focusing on the Sichuan Yanjiang Expressway project in China.The findings demonstrate that TLS-UAV technology enhanced both spatial coverage and data density in slope modeling.Through integrated algorithmic analysis,rock discontinuities within heterogeneous datasets were systematically identified,enabling quantitative extraction and statistical analysis of key geometric parameters,including orientation,trace length,spacing,and roughness.Furthermore,quantitative models were developed for cohesion,friction angle and the morphology parameter M of in situ discontinuities,respectively,facilitating efficient mechanical parameter acquisition.A novel rock mass hazard index(RHI)was developed incorporating discontinuity geometric rating(DGR),discontinuity mechanical rating(DMR),and slope mass rating(SMR).Field validation confirmed the methodology's effectiveness in evaluating risk levels and spatial heterogeneity of rock mass hazard sources,revealing the contribution of different discontinuity sets to the rock mass hazard and identifying the primary discontinuity sets controlling instability mechanisms.This study is of great significance for evaluating discontinuity-controlled rock mass hazard sources and preventing rockfall disasters.展开更多
Desulfurization of CaO–Al_(2)O_(3) particles in molten steel was observed in situ using high-temperature confocal scanning laser microscopy.The effects of the aluminum and silicon contents of molten steel on desulfur...Desulfurization of CaO–Al_(2)O_(3) particles in molten steel was observed in situ using high-temperature confocal scanning laser microscopy.The effects of the aluminum and silicon contents of molten steel on desulfurization were analyzed.When the total aluminum content in the steel increased from 6 to 1100 ppm,the CaS content in CaO–Al_(2)O_(3) particles increased from 2.1wt%to 84.84wt%after the reaction for 90 s.Furthermore,when the silicon content in the steel increased from 0.01wt%to 2.20wt%,the CaS content in CaO–Al_(2)O_(3) particles increased from 1.53wt%to 79.01wt%after the reaction for 90 s.This indicates that the increase in the aluminum and silicon contents of the steel promoted the desulfurization of CaO–Al_(2)O_(3) particles.A kinetic model was established to predict the CaO–Al_(2)O_(3) particles composition,and the diffusion coefficient of sulfur in CaO–Al_(2)O_(3) particles was 9.375×10^(−10)m^(2)·s^(−1) at 1600℃,which provided a new method for the calculation of diffusion coefficient.展开更多
Objective:To explore the application effect of digital intraoral scanning impression technique in oral implant restoration for periodontitis patients and analyze its impact on patients’Visual Analogue Scale(VAS)score...Objective:To explore the application effect of digital intraoral scanning impression technique in oral implant restoration for periodontitis patients and analyze its impact on patients’Visual Analogue Scale(VAS)scores.Methods:A total of 80 periodontitis patients who received implant restoration in our hospital from May 2023 to May 2025 were selected as research subjects.They were randomly divided into an observation group and a control group using a random number table method,with 40 cases in each group.The observation group used the digital intraoral scanning impression technique to obtain impressions,while the control group used the traditional silicone rubber impression technique.The impression-taking time,the number of prostheses try-ins,implant survival rate,periodontal health indicators(probing depth,gingival index,bleeding index),and VAS scores(pain during treatment and comfort after restoration)were compared between the two groups.Results:The observation group was superior to the control group in terms of impression-taking time,the number of prostheses try-ins,and implant survival rate(p<0.05).Six months after restoration,the improvement in periodontal health indicators in the observation group was significantly better than that in the control group(p<0.05).In addition,the pain VAS score of the observation group during treatment was lower than that of the control group,and the comfort VAS score after restoration was higher than that of the control group(p<0.05).Conclusion:Digital intraoral scanning impression technology can effectively enhance the efficiency and success rate of implant restoration in periodontitis patients,improve periodontal health,alleviate patients’discomfort during treatment,and increase post-restoration comfort,demonstrating high clinical application value.展开更多
为解决现有辨识方法在针对耦合的次/超同步振荡参数提取过程中的噪声适应性差和模态混叠问题,该文提出了一种自适应的变分模态分解法(variational mode decomposition,VMD),定义残差损失总熵、中心频率的切比雪夫距离以及边缘熵共同决...为解决现有辨识方法在针对耦合的次/超同步振荡参数提取过程中的噪声适应性差和模态混叠问题,该文提出了一种自适应的变分模态分解法(variational mode decomposition,VMD),定义残差损失总熵、中心频率的切比雪夫距离以及边缘熵共同决定分解模态数和带宽,结合最小二乘-旋转不变技术(total least square-estimating signal parameter via rotational invariance techniques,TLS-ESPRIT)对分解出的振荡分量进行参数辨识,无需另外使用降噪算法。通过复合信号测试法、PSCAD/EMTDC电磁暂态仿真法验证了所提方法的有效性。最后,将所提方法与改进Prony算法、MCEEMD法在不同噪声水平和振荡频率下进行对比,结果表明,所提方法能够有效地抑制原始信号的噪声干扰,对耦合的次/超同步振荡信号分解更加准确,参数辨识结果可靠性较高,对风电系统振荡溯源、改善系统阻尼具有一定的参考意义。展开更多
The characteristics of nonmetallic inclusions formed during steel production have a significant influence on steel performance.In this paper,studies on inclusions using confocal scanning laser microscopy(CSLM)are revi...The characteristics of nonmetallic inclusions formed during steel production have a significant influence on steel performance.In this paper,studies on inclusions using confocal scanning laser microscopy(CSLM)are reviewed and summarized,particularly the col-lision of various inclusions,dissolution of inclusions in liquid slag,and reactions between inclusions and steel.Solid inclusions exhibited a high collision tendency,whereas pure liquid inclusions exhibited minimal collisions because of the small attraction force induced by their<90°contact angle with molten steel.The collision of complex inclusions in molten steel was not included in the scope of this study and should be evaluated in future studies.Higher CaO/Al_(2)O_(3)and CaO/SiO_(2)ratios in liquid slag promoted the dissolution of Al_(2)O_(3)-based in-clusions.The formation of solid phases in the slag should be prevented to improve dissolution of inclusions.To accurately simulate the dissolution of inclusions in liquid slag,in-situ observation of the dissolution of inclusions at the steel-slag interface is necessary.Using a combination of CSLM and scanning electron microscopy-energy dispersive spectroscopy,the composition and morphological evolution of the inclusions during their modification by the dissolved elements in steel were observed and analyzed.Although the in-situ observa-tion of MnS and TiN precipitations has been widely studied,the in-situ observation of the evolution of oxide inclusions in steel during so-lidification and heating processes has rarely been reported.The effects of temperature,heating and cooling rates,and inclusion character-istics on the formation of acicular ferrites(AFs)have been widely studied.At a cooling rate of 3-5 K/s,the order of AF growth rate in-duced by different inclusions,as reported in literature,is Ti-O<Ti-Ca-Zr-Al-O<Mg-O<Ti-Zr-Al-O<Mn-Ti-Al-O<Ti-Al-O<Zr-Ti-Al-O.Further comprehensive experiments are required to investigate the quantitative relationship between the formation of AFs and inclusions.展开更多
Unmanned aerial vehicle laser scanning(ULS)and terrestrial laser scanning(TLS)systems are effective ways to capture forest structures from top and side views,respectively.The registration of TLS and ULS data is a prer...Unmanned aerial vehicle laser scanning(ULS)and terrestrial laser scanning(TLS)systems are effective ways to capture forest structures from top and side views,respectively.The registration of TLS and ULS data is a prerequisite for a comprehensive forest structure representation.Conventional registration methods based on geometric features(e.g.,points,lines,and planes)are likely to fail due to the irregular natural point distributions of forest point clouds.Currently,automatic registration methods for forest point clouds typically rely on tree attributes(such as tree position and stem diameter).However,these methods are often unsuitable for forests with diverse compositions,complex terrains,irregular tree layouts,and insufficient common trees.In this study,an automated method is proposed to register ULS and TLS forest point clouds using ground points as registration primitives,which operates independently of tree attribute extraction and is estimated to reduce processing time by over 50%.A new evaluation method for registration accuracy evaluation is proposed,where transformation parameters from each TLS scan to the ULS obtained by the proposed registration algorithm are used to derive transformation parameters between TLS scans,which are then compared to reference parameters obtained using artificial spherical targets.Conventional ULS-TLS registration evaluation methods mostly rely on the manual corresponding points selection that is subject to inherent subjective errors,or control points in both TLS and ULS data that are difficult to collect.The proposed method presents an objective and accurate solution for ULS-TLS registration accuracy evaluation that effectively eliminates these limitations.The proposed method was tested on 12 plots with diverse stem densities,tree species,and altitudes located in a mountain forest.A total of 124 TLS scans were successfully registered to ULS data.The registration accuracy was assessed using both the conventional evaluation method and the proposed new evaluation method,with average rotation errors of 2.03 and 2.06 mrad,and average translation errors of 7.63 and 6.51 cm,respectively.The registration accuracies demonstrate that the proposed algorithm effectively and accurately registers TLS to ULS point clouds.展开更多
The high-temperature dissolution behavior of primary carbides in samples taken from GCr15 continuous-casting bloom was observed in-situ by confocal laser scanning microscopy.Equations were fitted to the dissolution ki...The high-temperature dissolution behavior of primary carbides in samples taken from GCr15 continuous-casting bloom was observed in-situ by confocal laser scanning microscopy.Equations were fitted to the dissolution kinetics of primary carbides during either heating or soaking.Dissolution of carbides proceeded in three stages(fast→slow→faster)as either temperature or holding time was increased.During the heating process and during the first and third stages of the soaking process,the original size of the carbides determined the steepness of the slope,but during the middle(“slow”)stage of the soaking process,the slope remained zero.The initial size of the carbides varied greatly,but their final dissolution temperature fell within the narrow range of 1210-1235℃,and the holding time remained within 50 min.Fractal analysis was used to study the morphological characteristics of small and medium-sized carbides during the dissolution process.According to changes in the fractal dimension before and after soaking,the carbides tended to evolve towards a more regular morphology.展开更多
The centroid coordinate serves as a critical control parameter in motion systems,including aircraft,missiles,rockets,and drones,directly influencing their motion dynamics and control performance.Traditional methods fo...The centroid coordinate serves as a critical control parameter in motion systems,including aircraft,missiles,rockets,and drones,directly influencing their motion dynamics and control performance.Traditional methods for centroid measurement often necessitate custom equipment and specialized positioning devices,leading to high costs and limited accuracy.Here,we present a centroid measurement method that integrates 3D scanning technology,enabling accurate measurement of centroid across various types of objects without the need for specialized positioning fixtures.A theoretical framework for centroid measurement was established,which combined the principle of the multi-point weighing method with 3D scanning technology.The measurement accuracy was evaluated using a designed standard component.Experimental results demonstrate that the discrepancies between the theoretical and the measured centroid of a standard component with various materials and complex shapes in the X,Y,and Z directions are 0.003 mm,0.009 mm,and 0.105 mm,respectively,yielding a spatial deviation of 0.106 mm.Qualitative verification was conducted through experimental validation of three distinct types.They confirmed the reliability of the proposed method,which allowed for accurate centroid measurements of various products without requiring positioning fixtures.This advancement significantly broadened the applicability and scope of centroid measurement devices,offering new theoretical insights and methodologies for the measurement of complex parts and systems.展开更多
To investigate the nucleation behavior during the single-phased metallic solidification process,the commercial ultrapure ferritic stainless steels with no(Initial steel)and various melt treatments(R1,MR1,Y2,MY1,and M1...To investigate the nucleation behavior during the single-phased metallic solidification process,the commercial ultrapure ferritic stainless steels with no(Initial steel)and various melt treatments(R1,MR1,Y2,MY1,and M1 steels)were used to carry out the differential scanning colorimetry(DSC)and high-temperature confocal laser scanning microscope(HT-CLSM)experiments.Based on the results of DSC experiments,the equilibrium solidification process as well as the relationship among the critical undercooling degree(△T_(c)^(DSC)),latent heat of fusion/crystallization(△H_(f)/△H_(c)),equiaxed grain ratio(ER),and average grain size(△_(ave)^(ingot))was revealed.ER is increased with the decreasing△T_(c)^(DSC)and increasing△H_(f)/△H_(c);however,△_(ave)^(ingot)is decreased with them.Referring to the results of HT-CLSM experiments,the average sizes of micro-/macrostructures(d_(ave)/D_(ave)/)are decreased with the increasing cooling rate,as well as the difference between and apparent critical undercooling degree(△T_(c)^(CLSM))was revealed.The heterogeneous nucleation of the crystal nuclei occurs only if△T_(c)^(CLSM)>△T_(c)^(DSC).Combining with the interfacial wetting-lattice mismatch heterogeneous nucleation model,the dynamic mechanism of the metallic solidification was revealed.The as-cast grains of the melt-treated samples were obviously refined,owing to the much higher actual heterogeneous nucleation rates(I_(heter.,i))obtained through melt treatments,and the heterogeneous nucleation rates(I_(heter.,ij))for all samples are increased with the cooling rates,firmly confirming that the as-cast grains of each sample could be refined by the increasing cooling rates.展开更多
We have constructed the robust and highfield-stability scanning tunneling microscopy(STM)system which is equipped with a 12 Tsuperconductor magnet and the He-3 cryostat,obtaining the high-quality data of graphite whic...We have constructed the robust and highfield-stability scanning tunneling microscopy(STM)system which is equipped with a 12 Tsuperconductor magnet and the He-3 cryostat,obtaining the high-quality data of graphite which can be clearly characterized up to the 12-T high magnetic field and bulk 2H-NbSe2 whose vortex structure and surface defects can be clearly visualized by the scanning and dI/dV mapping.The pivotal factor of our superior data stems from the sapphire frame and its unique structure,which ensure an exceptional performance for the noise,which has the current spectral density low to 2×10^(-13)A√Hz at the low frequency with the cut-off frequency of 250 Hz and the engaging status,of vibration,promising to the robust platform for the investigation of the surface of materials.The low drifting rate from the image of graphite is v_(x)=-8:79×10^(-7)nm/s and v_(y)=-3.26×10^(-6)nm/s at 12 T and 0.3 K.Besides,equipped with the high-capacity He-3 cryostat(with 15 normal temperature and pressure liter He-3 gas),the system,which has the base temperature for 0.28 K,can operate at the low temperature for more than 72 h,ensuring the enduring research at the sub-Kelvin temperature for the dI/dV mapping and large-scale scanning.When the magnetic field is applied up to 12 T,the STM system also obtains the excellent-clarity and undistorted images of graphite,which proves the outstanding performance of the system at the high-field researches.展开更多
AIM:To evaluate retinal hemoglobin oxygen saturation in myopic eyes by scanning laser ophthalmoscope(SLO)and to assess its correlations with different severity of myopia.METHODS:Sixty-one eyes from 61 patients were in...AIM:To evaluate retinal hemoglobin oxygen saturation in myopic eyes by scanning laser ophthalmoscope(SLO)and to assess its correlations with different severity of myopia.METHODS:Sixty-one eyes from 61 patients were included and subdivided into three groups according to their refractive errors:high myopia group[20 eyes,spherical equivalent(SE)≤-6 D];low and moderate myopia(22 eyes,-6.0<SE≤-0.5 D);normal(19 eyes,-0.5<SE<+0.5 D).All subjects underwent SLO imaging with dual lasers(532 nm and 633 nm).The oxygen saturations of hemoglobin in arteries(SO_(2)A)and veins(SO_(2)V),and their differences(SO_(2)AV)were estimated from the optical densities of the vessels on the images at the two wavelengths.Pearson’s or Spearman’s rank correlation coefficient were calculated to assess the correlation between retinal hemoglobin oxygen saturation and refractive error/axial length(AL).RESULTS:For the retinal oxygen saturation,the SO_(2)V in high myopia group(73.21%±21.42%)was significantly higher than that in normal group(55.81%±21.69%)and low and moderate myopia group(56.88%±13.83%,P<0.05).The SE was significantly correlated with SO_(2)A(r=-0.30)and SO_(2)V(r=-0.36;P<0.05),and AL was also significantly correlated with SO_(2)A(r=0.27)and SO_(2)V(r=0.30;P<0.05).No significant correlations were found between SO_(2)AV and SE and AL(P>0.05).CONCLUSION:SO_(2)A and SO_(2)V increased in more myopic eye based on SLO measurements.Further studies are warranted to investigate the changes of retinal hemoglobin oxygen saturation in myopia with different methods.展开更多
The assembly behaviors of two low-symmetric carboxylic acid molecules(50-(6-carboxynaphthalen-2-yl)-[1,10:30,100-triphenyl]-3,400,5-tricarboxylic acid(CTTA)and 30,50-bis(6-carboxynaphthalen-2-yl)-[1,10-biphenyl]-3,5-d...The assembly behaviors of two low-symmetric carboxylic acid molecules(50-(6-carboxynaphthalen-2-yl)-[1,10:30,100-triphenyl]-3,400,5-tricarboxylic acid(CTTA)and 30,50-bis(6-carboxynaphthalen-2-yl)-[1,10-biphenyl]-3,5-dicarboxylic acid(BCBDA))containing naphthalene rings on graphite surfaces have been investigated using scanning tunneling microscopy(STM).The transformation of nanostructures induced by the second components(EDA and PEBP-C4)have been also examined.Both CTTA and BCBDA molecules self-assemble at the 1-heptanoic acid(HA)/HOPG interface,forming porous network structures.The dimer represents the most elementary building unit due to the formation of double hydrogen bonds.Moreover,the flipping of naphthalene ring results in the isomerization of BCBDA molecule.The introduction of carboxylic acid derivative EDA disrupts the dimer,which subsequently undergoes a structural conformation to form a novel porous structure.Furthermore,upon the addition of pyridine derivative PEBP-C4,N–H⋯O hydrogen bonds are the dominant forces driving the three coassembled structures.We have also conducted density functional theory(DFT)calculations to determine the molecular conformation and analyze the mechanisms underlying the formation of nanostructures.展开更多
基金support from the National Natural Science Foundation of China(Grant Nos.42177142 and 52378477)the Key Research and Development Program of Shaanxi(Grant No.2023-YBSF-486).
文摘The identification of rock mass hazard sources is fundamental for preventing rockfall and landslide disasters in mountainous regions,with rock mass structural characteristics playing a vital role in hazard assessment.In this study,terrestrial laser scanning(TLS)and unmanned aerial vehicle(UAV)technologies were integrated to enhance the evaluation methodology for rock mass hazard sources,focusing on the Sichuan Yanjiang Expressway project in China.The findings demonstrate that TLS-UAV technology enhanced both spatial coverage and data density in slope modeling.Through integrated algorithmic analysis,rock discontinuities within heterogeneous datasets were systematically identified,enabling quantitative extraction and statistical analysis of key geometric parameters,including orientation,trace length,spacing,and roughness.Furthermore,quantitative models were developed for cohesion,friction angle and the morphology parameter M of in situ discontinuities,respectively,facilitating efficient mechanical parameter acquisition.A novel rock mass hazard index(RHI)was developed incorporating discontinuity geometric rating(DGR),discontinuity mechanical rating(DMR),and slope mass rating(SMR).Field validation confirmed the methodology's effectiveness in evaluating risk levels and spatial heterogeneity of rock mass hazard sources,revealing the contribution of different discontinuity sets to the rock mass hazard and identifying the primary discontinuity sets controlling instability mechanisms.This study is of great significance for evaluating discontinuity-controlled rock mass hazard sources and preventing rockfall disasters.
基金supported by the National Key R&D Program of China(No.2023YFB3709900)the National Nature Science Foundation of China(No.U22A20171)+1 种基金the China Baowu Low Carbon Metallurgy Innovation Foundation(No.BWLCF202315)the High Steel Center(HSC)at North China University of Technology and University of Science and Technology Beijing,China.
文摘Desulfurization of CaO–Al_(2)O_(3) particles in molten steel was observed in situ using high-temperature confocal scanning laser microscopy.The effects of the aluminum and silicon contents of molten steel on desulfurization were analyzed.When the total aluminum content in the steel increased from 6 to 1100 ppm,the CaS content in CaO–Al_(2)O_(3) particles increased from 2.1wt%to 84.84wt%after the reaction for 90 s.Furthermore,when the silicon content in the steel increased from 0.01wt%to 2.20wt%,the CaS content in CaO–Al_(2)O_(3) particles increased from 1.53wt%to 79.01wt%after the reaction for 90 s.This indicates that the increase in the aluminum and silicon contents of the steel promoted the desulfurization of CaO–Al_(2)O_(3) particles.A kinetic model was established to predict the CaO–Al_(2)O_(3) particles composition,and the diffusion coefficient of sulfur in CaO–Al_(2)O_(3) particles was 9.375×10^(−10)m^(2)·s^(−1) at 1600℃,which provided a new method for the calculation of diffusion coefficient.
文摘Objective:To explore the application effect of digital intraoral scanning impression technique in oral implant restoration for periodontitis patients and analyze its impact on patients’Visual Analogue Scale(VAS)scores.Methods:A total of 80 periodontitis patients who received implant restoration in our hospital from May 2023 to May 2025 were selected as research subjects.They were randomly divided into an observation group and a control group using a random number table method,with 40 cases in each group.The observation group used the digital intraoral scanning impression technique to obtain impressions,while the control group used the traditional silicone rubber impression technique.The impression-taking time,the number of prostheses try-ins,implant survival rate,periodontal health indicators(probing depth,gingival index,bleeding index),and VAS scores(pain during treatment and comfort after restoration)were compared between the two groups.Results:The observation group was superior to the control group in terms of impression-taking time,the number of prostheses try-ins,and implant survival rate(p<0.05).Six months after restoration,the improvement in periodontal health indicators in the observation group was significantly better than that in the control group(p<0.05).In addition,the pain VAS score of the observation group during treatment was lower than that of the control group,and the comfort VAS score after restoration was higher than that of the control group(p<0.05).Conclusion:Digital intraoral scanning impression technology can effectively enhance the efficiency and success rate of implant restoration in periodontitis patients,improve periodontal health,alleviate patients’discomfort during treatment,and increase post-restoration comfort,demonstrating high clinical application value.
文摘为解决现有辨识方法在针对耦合的次/超同步振荡参数提取过程中的噪声适应性差和模态混叠问题,该文提出了一种自适应的变分模态分解法(variational mode decomposition,VMD),定义残差损失总熵、中心频率的切比雪夫距离以及边缘熵共同决定分解模态数和带宽,结合最小二乘-旋转不变技术(total least square-estimating signal parameter via rotational invariance techniques,TLS-ESPRIT)对分解出的振荡分量进行参数辨识,无需另外使用降噪算法。通过复合信号测试法、PSCAD/EMTDC电磁暂态仿真法验证了所提方法的有效性。最后,将所提方法与改进Prony算法、MCEEMD法在不同噪声水平和振荡频率下进行对比,结果表明,所提方法能够有效地抑制原始信号的噪声干扰,对耦合的次/超同步振荡信号分解更加准确,参数辨识结果可靠性较高,对风电系统振荡溯源、改善系统阻尼具有一定的参考意义。
基金supported by the National Key R&D Program(No.2023YFB3709900)the National Nature Science Foundation of China(No.U22A20171)+2 种基金China Baowu Low Carbon Metallurgy Innovation Foundation(No.BWLCF202315)the High Steel Center(HSC)at North China University of TechnologyUniversity of Science and Technology Beijing,China.
文摘The characteristics of nonmetallic inclusions formed during steel production have a significant influence on steel performance.In this paper,studies on inclusions using confocal scanning laser microscopy(CSLM)are reviewed and summarized,particularly the col-lision of various inclusions,dissolution of inclusions in liquid slag,and reactions between inclusions and steel.Solid inclusions exhibited a high collision tendency,whereas pure liquid inclusions exhibited minimal collisions because of the small attraction force induced by their<90°contact angle with molten steel.The collision of complex inclusions in molten steel was not included in the scope of this study and should be evaluated in future studies.Higher CaO/Al_(2)O_(3)and CaO/SiO_(2)ratios in liquid slag promoted the dissolution of Al_(2)O_(3)-based in-clusions.The formation of solid phases in the slag should be prevented to improve dissolution of inclusions.To accurately simulate the dissolution of inclusions in liquid slag,in-situ observation of the dissolution of inclusions at the steel-slag interface is necessary.Using a combination of CSLM and scanning electron microscopy-energy dispersive spectroscopy,the composition and morphological evolution of the inclusions during their modification by the dissolved elements in steel were observed and analyzed.Although the in-situ observa-tion of MnS and TiN precipitations has been widely studied,the in-situ observation of the evolution of oxide inclusions in steel during so-lidification and heating processes has rarely been reported.The effects of temperature,heating and cooling rates,and inclusion character-istics on the formation of acicular ferrites(AFs)have been widely studied.At a cooling rate of 3-5 K/s,the order of AF growth rate in-duced by different inclusions,as reported in literature,is Ti-O<Ti-Ca-Zr-Al-O<Mg-O<Ti-Zr-Al-O<Mn-Ti-Al-O<Ti-Al-O<Zr-Ti-Al-O.Further comprehensive experiments are required to investigate the quantitative relationship between the formation of AFs and inclusions.
基金supported partially by the National Key Research and Development Program of China(No.2023YFF1303901)the National Natural Science Foundation of China(Nos.32171789,12411530088,and 32371654)the Joint Open Funded Project of State Key Laboratory of Geo-Information Engineering and Key Laboratory of the Ministry of Natural Resources for Surveying and Mapping Science and Geo-spatial Information Technology(No.2022-02-02).
文摘Unmanned aerial vehicle laser scanning(ULS)and terrestrial laser scanning(TLS)systems are effective ways to capture forest structures from top and side views,respectively.The registration of TLS and ULS data is a prerequisite for a comprehensive forest structure representation.Conventional registration methods based on geometric features(e.g.,points,lines,and planes)are likely to fail due to the irregular natural point distributions of forest point clouds.Currently,automatic registration methods for forest point clouds typically rely on tree attributes(such as tree position and stem diameter).However,these methods are often unsuitable for forests with diverse compositions,complex terrains,irregular tree layouts,and insufficient common trees.In this study,an automated method is proposed to register ULS and TLS forest point clouds using ground points as registration primitives,which operates independently of tree attribute extraction and is estimated to reduce processing time by over 50%.A new evaluation method for registration accuracy evaluation is proposed,where transformation parameters from each TLS scan to the ULS obtained by the proposed registration algorithm are used to derive transformation parameters between TLS scans,which are then compared to reference parameters obtained using artificial spherical targets.Conventional ULS-TLS registration evaluation methods mostly rely on the manual corresponding points selection that is subject to inherent subjective errors,or control points in both TLS and ULS data that are difficult to collect.The proposed method presents an objective and accurate solution for ULS-TLS registration accuracy evaluation that effectively eliminates these limitations.The proposed method was tested on 12 plots with diverse stem densities,tree species,and altitudes located in a mountain forest.A total of 124 TLS scans were successfully registered to ULS data.The registration accuracy was assessed using both the conventional evaluation method and the proposed new evaluation method,with average rotation errors of 2.03 and 2.06 mrad,and average translation errors of 7.63 and 6.51 cm,respectively.The registration accuracies demonstrate that the proposed algorithm effectively and accurately registers TLS to ULS point clouds.
基金supported by Independent Research Project of State Key Laboratory of Advanced Special Steel,Shanghai Key Laboratory of Advanced Ferrometallurgy,Shanghai University(SKLASS-2023-Z13)the Science and Technology Commission of Shanghai Municipality(No.19DZ2270200)+1 种基金A portion of the work was performed at US National High Magnetic Field Laboratory,which is supported by the National Science Foundation(Cooperative Agreement No.DMR-1157490 and DMR-1644779)the State of Florida.Thanks also to Mary Tyler for editing.
文摘The high-temperature dissolution behavior of primary carbides in samples taken from GCr15 continuous-casting bloom was observed in-situ by confocal laser scanning microscopy.Equations were fitted to the dissolution kinetics of primary carbides during either heating or soaking.Dissolution of carbides proceeded in three stages(fast→slow→faster)as either temperature or holding time was increased.During the heating process and during the first and third stages of the soaking process,the original size of the carbides determined the steepness of the slope,but during the middle(“slow”)stage of the soaking process,the slope remained zero.The initial size of the carbides varied greatly,but their final dissolution temperature fell within the narrow range of 1210-1235℃,and the holding time remained within 50 min.Fractal analysis was used to study the morphological characteristics of small and medium-sized carbides during the dissolution process.According to changes in the fractal dimension before and after soaking,the carbides tended to evolve towards a more regular morphology.
基金supported by National Natural Science Foundation of China(No.52176122).
文摘The centroid coordinate serves as a critical control parameter in motion systems,including aircraft,missiles,rockets,and drones,directly influencing their motion dynamics and control performance.Traditional methods for centroid measurement often necessitate custom equipment and specialized positioning devices,leading to high costs and limited accuracy.Here,we present a centroid measurement method that integrates 3D scanning technology,enabling accurate measurement of centroid across various types of objects without the need for specialized positioning fixtures.A theoretical framework for centroid measurement was established,which combined the principle of the multi-point weighing method with 3D scanning technology.The measurement accuracy was evaluated using a designed standard component.Experimental results demonstrate that the discrepancies between the theoretical and the measured centroid of a standard component with various materials and complex shapes in the X,Y,and Z directions are 0.003 mm,0.009 mm,and 0.105 mm,respectively,yielding a spatial deviation of 0.106 mm.Qualitative verification was conducted through experimental validation of three distinct types.They confirmed the reliability of the proposed method,which allowed for accurate centroid measurements of various products without requiring positioning fixtures.This advancement significantly broadened the applicability and scope of centroid measurement devices,offering new theoretical insights and methodologies for the measurement of complex parts and systems.
基金supported by the National Natural Science Foundation of China(Grant Nos.52274339,52174321,52074186,and 52104337)Natural Science Foundation of Jiangsu Province(Grant No.BK20231317)China Baowu Low-Carbon Metallurgy Innovation Fund(Grant No.BWLCF202108).
文摘To investigate the nucleation behavior during the single-phased metallic solidification process,the commercial ultrapure ferritic stainless steels with no(Initial steel)and various melt treatments(R1,MR1,Y2,MY1,and M1 steels)were used to carry out the differential scanning colorimetry(DSC)and high-temperature confocal laser scanning microscope(HT-CLSM)experiments.Based on the results of DSC experiments,the equilibrium solidification process as well as the relationship among the critical undercooling degree(△T_(c)^(DSC)),latent heat of fusion/crystallization(△H_(f)/△H_(c)),equiaxed grain ratio(ER),and average grain size(△_(ave)^(ingot))was revealed.ER is increased with the decreasing△T_(c)^(DSC)and increasing△H_(f)/△H_(c);however,△_(ave)^(ingot)is decreased with them.Referring to the results of HT-CLSM experiments,the average sizes of micro-/macrostructures(d_(ave)/D_(ave)/)are decreased with the increasing cooling rate,as well as the difference between and apparent critical undercooling degree(△T_(c)^(CLSM))was revealed.The heterogeneous nucleation of the crystal nuclei occurs only if△T_(c)^(CLSM)>△T_(c)^(DSC).Combining with the interfacial wetting-lattice mismatch heterogeneous nucleation model,the dynamic mechanism of the metallic solidification was revealed.The as-cast grains of the melt-treated samples were obviously refined,owing to the much higher actual heterogeneous nucleation rates(I_(heter.,i))obtained through melt treatments,and the heterogeneous nucleation rates(I_(heter.,ij))for all samples are increased with the cooling rates,firmly confirming that the as-cast grains of each sample could be refined by the increasing cooling rates.
基金the CHMFL(Chinese High Magnetic Field Laboratory)faculty for the operation of the magnet platformsupported by the National Key R&D Program of China(No.2023YFA 1607701)+3 种基金the National Natural Science Foundation of China(Nos.51627901,U1932216,and 12004386)the Maintenance and Renovation Project for CAS Major Scientific and Technological Infrastructure(Nos.DSSWXGZ-2019-0011 and DSSWXGZ-2021-0006)the Chinese Academy of Sciences Scientific Research Equipment(No.YJKYYQ20190014)the Hefei Science Center CAS(No.2021HSC-UE010)。
文摘We have constructed the robust and highfield-stability scanning tunneling microscopy(STM)system which is equipped with a 12 Tsuperconductor magnet and the He-3 cryostat,obtaining the high-quality data of graphite which can be clearly characterized up to the 12-T high magnetic field and bulk 2H-NbSe2 whose vortex structure and surface defects can be clearly visualized by the scanning and dI/dV mapping.The pivotal factor of our superior data stems from the sapphire frame and its unique structure,which ensure an exceptional performance for the noise,which has the current spectral density low to 2×10^(-13)A√Hz at the low frequency with the cut-off frequency of 250 Hz and the engaging status,of vibration,promising to the robust platform for the investigation of the surface of materials.The low drifting rate from the image of graphite is v_(x)=-8:79×10^(-7)nm/s and v_(y)=-3.26×10^(-6)nm/s at 12 T and 0.3 K.Besides,equipped with the high-capacity He-3 cryostat(with 15 normal temperature and pressure liter He-3 gas),the system,which has the base temperature for 0.28 K,can operate at the low temperature for more than 72 h,ensuring the enduring research at the sub-Kelvin temperature for the dI/dV mapping and large-scale scanning.When the magnetic field is applied up to 12 T,the STM system also obtains the excellent-clarity and undistorted images of graphite,which proves the outstanding performance of the system at the high-field researches.
基金Supported by Shantou Science and Technology Project(No.190917155269927)2020 Li Ka Shing Foundation Cross-Disciplinary Research Grant(No.2020LKSFG06B).
文摘AIM:To evaluate retinal hemoglobin oxygen saturation in myopic eyes by scanning laser ophthalmoscope(SLO)and to assess its correlations with different severity of myopia.METHODS:Sixty-one eyes from 61 patients were included and subdivided into three groups according to their refractive errors:high myopia group[20 eyes,spherical equivalent(SE)≤-6 D];low and moderate myopia(22 eyes,-6.0<SE≤-0.5 D);normal(19 eyes,-0.5<SE<+0.5 D).All subjects underwent SLO imaging with dual lasers(532 nm and 633 nm).The oxygen saturations of hemoglobin in arteries(SO_(2)A)and veins(SO_(2)V),and their differences(SO_(2)AV)were estimated from the optical densities of the vessels on the images at the two wavelengths.Pearson’s or Spearman’s rank correlation coefficient were calculated to assess the correlation between retinal hemoglobin oxygen saturation and refractive error/axial length(AL).RESULTS:For the retinal oxygen saturation,the SO_(2)V in high myopia group(73.21%±21.42%)was significantly higher than that in normal group(55.81%±21.69%)and low and moderate myopia group(56.88%±13.83%,P<0.05).The SE was significantly correlated with SO_(2)A(r=-0.30)and SO_(2)V(r=-0.36;P<0.05),and AL was also significantly correlated with SO_(2)A(r=0.27)and SO_(2)V(r=0.30;P<0.05).No significant correlations were found between SO_(2)AV and SE and AL(P>0.05).CONCLUSION:SO_(2)A and SO_(2)V increased in more myopic eye based on SLO measurements.Further studies are warranted to investigate the changes of retinal hemoglobin oxygen saturation in myopia with different methods.
基金financially supported by the National Natural Science Foundation of China(No.22272039)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB36000000)+1 种基金the Youth Program of the Liaoning Education Department(No.LJKQZ20222280)the Jilin Chinese Academy of Sciences-Yanshen Technology Co.,Ltd.
文摘The assembly behaviors of two low-symmetric carboxylic acid molecules(50-(6-carboxynaphthalen-2-yl)-[1,10:30,100-triphenyl]-3,400,5-tricarboxylic acid(CTTA)and 30,50-bis(6-carboxynaphthalen-2-yl)-[1,10-biphenyl]-3,5-dicarboxylic acid(BCBDA))containing naphthalene rings on graphite surfaces have been investigated using scanning tunneling microscopy(STM).The transformation of nanostructures induced by the second components(EDA and PEBP-C4)have been also examined.Both CTTA and BCBDA molecules self-assemble at the 1-heptanoic acid(HA)/HOPG interface,forming porous network structures.The dimer represents the most elementary building unit due to the formation of double hydrogen bonds.Moreover,the flipping of naphthalene ring results in the isomerization of BCBDA molecule.The introduction of carboxylic acid derivative EDA disrupts the dimer,which subsequently undergoes a structural conformation to form a novel porous structure.Furthermore,upon the addition of pyridine derivative PEBP-C4,N–H⋯O hydrogen bonds are the dominant forces driving the three coassembled structures.We have also conducted density functional theory(DFT)calculations to determine the molecular conformation and analyze the mechanisms underlying the formation of nanostructures.
