The fifth generation(5G)network communication systems operate in the millimeter waves and are expected to provide a much higher data rate in the multi-gigabit range,which is impossible to achieve using current wireles...The fifth generation(5G)network communication systems operate in the millimeter waves and are expected to provide a much higher data rate in the multi-gigabit range,which is impossible to achieve using current wireless services,including the sub-6 GHz band.In this work,we briefly review several existing designs of millimeter-wave phased arrays for 5G applications,beginning with the low-profile antenna array designs that either are fixed beam or scan the beam only in one plane.We then move on to array systems that offer two-dimensional(2D)scan capability,which is highly desirable for a majority of 5G applications.Next,in the main body of the paper,we discuss two different strategies for designing scanning arrays,both of which circumvent the use of conventional phase shifters to achieve beam scanning.We note that it is highly desirable to search for alternatives to conventional phase shifters in the millimeter-wave range because legacy phase shifters are both lossy and costly;furthermore,alternatives such as active phase shifters,which include radio frequency amplifiers,are both expensive and power-hungry.Given this backdrop,we propose two different antenna systems with potential for the desired 2D scan performance in the millimeter-wave range.The first of these is a Luneburg lens,which is excited either by a 2D waveguide array or by a microstrip patch antenna array to realize 2D scan capability.Next,for second design,we turn to phased-array designs in which the conventional phase shifter is replaced by switchable PIN diodes or varactor diodes,inserted between radiating slots in a waveguide to provide the desired phase shifts for scanning.Finally,we discuss several approaches to enhance the gain of the array by modifying the conventional array configurations.We describe novel techniques for realizing both one-dimensional(1D)and 2D scans by using a reconfigurable metasurface type of panels.展开更多
In conventional High Power Microwave(HPM)waveguide arrays of longitudinal shunt slots,the mutual coupling of slots in different waveguide can badly decrease the capability of wide-angle scanning of array.For this reas...In conventional High Power Microwave(HPM)waveguide arrays of longitudinal shunt slots,the mutual coupling of slots in different waveguide can badly decrease the capability of wide-angle scanning of array.For this reason,an L-band HPM waveguide array of longitudinal shunt slots was designed.The choke groove was adopted to restrain the mutual coupling of slots of the HPM array antenna.The results of simulation are:the scanning angle of array without choke groove structure with the gain of antenna decreased 3 dB is only 24.7°,and it is 33.0°for array with choke groove structure;the wideband of active reflection of array have been improved with choke groove structure,the bandwidth of VSWR≤3 of array with choke groove is 6.6%,and that is 5.0%without choke groove;the power-handling capacity of array antenna with scanning angle of 35°can reach 957 MW,which is a little less than that of array without scanning(1008MW).展开更多
In this review,research progress on the wideband wide-angle scanning two-dimensional phased arrays is summarized.The importance of the wideband and the wide-angle scanning characteristics for satellite communication i...In this review,research progress on the wideband wide-angle scanning two-dimensional phased arrays is summarized.The importance of the wideband and the wide-angle scanning characteristics for satellite communication is discussed.Issues like grating lobe avoidance,active reflection coefficient suppression and gain fluctuation reduction are emphasized in this review.Besides,techniques to address these issues and methods to realize the wideband wide-angle scanning phased array are reviewed.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
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
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
Metasurfaces composed of two-dimensional nanopillar arrays can manipulate light fields in desirable ways and exhibit the unique advantage of beam steering.Here,we experimentally demonstrate a metasurface-based wide-an...Metasurfaces composed of two-dimensional nanopillar arrays can manipulate light fields in desirable ways and exhibit the unique advantage of beam steering.Here,we experimentally demonstrate a metasurface-based wide-angle broadband all-dielectric blazed grating with an extreme incident angle of up to 80°,which is achieved by optimizing the wide-angle phase shifts and transmissivities of the unit cells.It exhibits a maximum diffraction efficiency of 72%and a high average efficiency of 64%over a wide range of incident angles from−80° to 45° at 1.55μm.Moreover,the proposed grating has a broad bandwidth of 200 nm(1.45-1.65μm),and average efficiencies of more than 50%can be achieved experimentally over the same incidence angles.Our results may pave the way for the creation of novel and efficient flat optical devices for wavefront control.展开更多
In this paper, the reactive splitter network and meta-surface are proposed to radiate the wide-beam isolated element pattern and suppress mutual coupling (MC) of the low-profile phased array with the triangular lattic...In this paper, the reactive splitter network and meta-surface are proposed to radiate the wide-beam isolated element pattern and suppress mutual coupling (MC) of the low-profile phased array with the triangular lattice, respectively. Thus, broadband wide-angle impedance matching (WAIM) is imple-mented to promote two-dimensional (2D) wide scanning. For the isolated element, to radiate the wide-beam patterns approximat-ing to the cosine form, two identical slots backed on one sub-strate integrated cavity are excited by the feeding network con-sisting of a reactive splitter and two striplines connected with splitter output paths. For adjacent elements staggered with each other, with the metasurface superstrate, the even-mode cou-pling voltages on the reactive splitter are cancelled out, yielding reduced MC. With the suppression of MC and the compensa-tion of isolated element patterns, WAIM is realized to achieve 2D wide-angle beam steering up to ± 65° in E-plane, ± 45° in H-plane and ± 60° in D-plane from 4.9 GHz to 5.85 GHz.展开更多
The emergent metagrating,with its unique and flexible beam shaping capabilities,offers new paths to efficient modulation of acoustic waves.In this work,an acoustic metagrating is demonstrated for high-efficiency and w...The emergent metagrating,with its unique and flexible beam shaping capabilities,offers new paths to efficient modulation of acoustic waves.In this work,an acoustic metagrating is demonstrated for high-efficiency and wide-angle anomalous refraction.It is shown that the normal reflection and transmission can be totally suppressed by properly modulating the amplitude and phase characteristics of the metagrating supercells for high-efficiency anomalous refraction.The anomalous refraction behavior is achieved in the wide range of incident angles from 28°to 78°,and the efficiency of-1st order diffraction is higher than 90%by finely designing the metagrating structure.The anomalous refraction behaviors are verified experimentally at incidence angle of 28°,45°,and 78°,respectively.The demonstrated metagrating is anticipated to possess efficient wide-angle composite wavefront engineering applications in such fields as communications.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
Manipulating and braiding Majorana zero modes(MZM)are a critical step toward realizing topological quantum computing.The primary challenge is controlling the vortex,which hosts the MZM,within a superconducting film in...Manipulating and braiding Majorana zero modes(MZM)are a critical step toward realizing topological quantum computing.The primary challenge is controlling the vortex,which hosts the MZM,within a superconducting film in a spatially precise manner.To address this,we developed a magnetic force-based vortex control technology using the STM system with a self-designed four-electrode piezo-scanner tube and investigated vortex manipulation on the NbSe_(2) superconducting film.We employed ferromagnetic tips to control the movement of vortex array induced by the tip's remanent magnetism.A magnetic core solenoid device was integrated into the STM system and a strong magnetic tip demagnetization technique was developed,providing a viable technical solution for further enabling single vortex manipulation.展开更多
Mitochondria play a crucial role in the physiological functions and energy metabolism of neurons,which can help in the understanding of complex biochemical reactions associated with various neurodegenerative diseases....Mitochondria play a crucial role in the physiological functions and energy metabolism of neurons,which can help in the understanding of complex biochemical reactions associated with various neurodegenerative diseases.Neurons,being highly differentiated terminal cells,require a greater number of mitochondria than ordinary cells to generate significant amounts of ATP,which is necessary for the growth of differentiated neuronal structures like axons and dendrites and the transmission of electrical signals along neuronal axons.Advancements in imaging technology,electrophysiology,and fluorescence targeting labeling have facilitated the study of mitochondrial movements in neurons and axons.However,disordered mitochondrial movements can hinder their analysis and characterization.Thus,it becomes necessary to artificially control their transport.Here,we demonstrate the utilization of scanning optical tweezers(SOTs)on the stable trapping and precise transport of soma or axon of neurons and enable.The presented method provides an optical approach to the control of mitochondria or other organelles in complex and variable biological environment.展开更多
Background:Contrast-enhanced magnetic resonance neurography(ceMRN)can enhance brachial plexus visualization and quality of imaging.However,the interval between contrast injection and scanning that provides the highest...Background:Contrast-enhanced magnetic resonance neurography(ceMRN)can enhance brachial plexus visualization and quality of imaging.However,the interval between contrast injection and scanning that provides the highest-quality images is not known.Methods:Fifteen patients underwent brachial plexus imaging using the 3D T2-NerveView sequence with a scanning duration of 5 min.A consecutive six-phase scan was initiated immediately at the start of contrast agent injection.Subsequently,all patients'images were classified into six groups according to the phases:group A(phase 1,delay 0 min),group B(phase 2,delay 5 min),group C(phase 3,delay 10 min),group D(phase 4,delay 15 min),group E(phase 5,delay 20 min),and group F(phase 6,delay 25 min).The image quality in each group was assessed based on nerve signal(signalnerve),muscle signal(signalmuscle),lymph node signal(signallymph node),background noise(BN),signal-to-noise ratio(SNR),contrast-to-noise ratio(CNR),and subjective score.Results:Signalnerve,signalmuscle,BN,and SNR did not significantly differ among the six groups(p>0.05).However,significant differences(p<0.05)were observed in signallymph node(F=16.067),CNR(F=9.495),and subjective score(χ^(2)=23.586).As the scanning delay increased,signallymph node intensity gradually increased whereas the CNR gradually decreased.The subjective score was significantly higher in groups B(4.830.24),C(4.900.21),D(4.870.30),E(4.830.31),and F(4.830.31)than in group A(4.470.30).Conclusion:We recommend performing brachial plexus ceMRN 5 min after contrast injection.With this delay,the brachial plexus can be visualized optimally with minimal interference from background signals.展开更多
In this paper,a dual-polarized antenna operating at 3.5 GHz is presented with 2D beam-scanning performance.The steerable beam is realized based on a 2×2 active reflective metasurface.The active metasurface is com...In this paper,a dual-polarized antenna operating at 3.5 GHz is presented with 2D beam-scanning performance.The steerable beam is realized based on a 2×2 active reflective metasurface.The active metasurface is composed of folded annular rings and cross dipoles embedded with voltage-controlled varactor diodes.By tuning the capacitance values of the varactors,the reflective phase of the metasurface is reconfigured to tilt the main beam.To verify the scanning performance,a prototype is fabricated and measured.At 3.5 GHz,the measured scanning ranges are from-25°to 29°and-27°to 29°in the XOZ and YOZ planes,respectively.展开更多
Welding quality of electron beam welded joint is usually susceptible to the stability of keyhole during welding process.The more stable the keyhole,the better the welding quality.To reveal the evolution mechanism of k...Welding quality of electron beam welded joint is usually susceptible to the stability of keyhole during welding process.The more stable the keyhole,the better the welding quality.To reveal the evolution mechanism of keyhole and welding quality of the electron beam welded joint of magnesium-gadolinium alloy under different scanning path,numerical simulation was conducted for the changes in morphology of keyhole and liquid flow in molten pool.The magnesium-gadolinium alloy was welded by electron beam in vacuum with two different scanning paths,sinusoid path and cochleoid path,indicating the identical heat input,welding speed,and focusing state.The stability of keyhole was mainly related to the frequency of keyhole collapse.When the sinusoid scanning path was adopted,the fluids both inside the molten pool and at keyhole wall were disorder,corresponding to the numerous independent vortices and dramatically chaotic flows at their junctions.The maximum velocity of fluids ranged from 0.79 m/s to 1.02 m/s.The average and maximum depth of keyhole were 3.48 mm and 4.51 mm,respectively,meaning that the keyhole collapsed frequently.As the scanning path was changed into cochleoid mode,the electron beam scanned in a homogeneous manner without abrupt change in direction and speed like sinusoid path at its peaks and troughs.The maximum velocity of fluids was more uniform without drastic variation,ranging from 0.90 m/s to 1.01 m/s.The average and maximum depth of keyhole were decreased to 3.30 mm and 4.05 mm,respectively,indicating the more stable keyhole and alleviated collapse.Both the actual in-situ capture of molten pool signature and porosity inside the weld corresponded to the analysis of the change in keyhole stability.展开更多
文摘The fifth generation(5G)network communication systems operate in the millimeter waves and are expected to provide a much higher data rate in the multi-gigabit range,which is impossible to achieve using current wireless services,including the sub-6 GHz band.In this work,we briefly review several existing designs of millimeter-wave phased arrays for 5G applications,beginning with the low-profile antenna array designs that either are fixed beam or scan the beam only in one plane.We then move on to array systems that offer two-dimensional(2D)scan capability,which is highly desirable for a majority of 5G applications.Next,in the main body of the paper,we discuss two different strategies for designing scanning arrays,both of which circumvent the use of conventional phase shifters to achieve beam scanning.We note that it is highly desirable to search for alternatives to conventional phase shifters in the millimeter-wave range because legacy phase shifters are both lossy and costly;furthermore,alternatives such as active phase shifters,which include radio frequency amplifiers,are both expensive and power-hungry.Given this backdrop,we propose two different antenna systems with potential for the desired 2D scan performance in the millimeter-wave range.The first of these is a Luneburg lens,which is excited either by a 2D waveguide array or by a microstrip patch antenna array to realize 2D scan capability.Next,for second design,we turn to phased-array designs in which the conventional phase shifter is replaced by switchable PIN diodes or varactor diodes,inserted between radiating slots in a waveguide to provide the desired phase shifts for scanning.Finally,we discuss several approaches to enhance the gain of the array by modifying the conventional array configurations.We describe novel techniques for realizing both one-dimensional(1D)and 2D scans by using a reconfigurable metasurface type of panels.
文摘In conventional High Power Microwave(HPM)waveguide arrays of longitudinal shunt slots,the mutual coupling of slots in different waveguide can badly decrease the capability of wide-angle scanning of array.For this reason,an L-band HPM waveguide array of longitudinal shunt slots was designed.The choke groove was adopted to restrain the mutual coupling of slots of the HPM array antenna.The results of simulation are:the scanning angle of array without choke groove structure with the gain of antenna decreased 3 dB is only 24.7°,and it is 33.0°for array with choke groove structure;the wideband of active reflection of array have been improved with choke groove structure,the bandwidth of VSWR≤3 of array with choke groove is 6.6%,and that is 5.0%without choke groove;the power-handling capacity of array antenna with scanning angle of 35°can reach 957 MW,which is a little less than that of array without scanning(1008MW).
基金This work is supported by the National Natural Science Foundation of China(Nos.61731005,61331007)the Outstanding Youth Foundation of Sichuan Province(No.2015JQ0011).
文摘In this review,research progress on the wideband wide-angle scanning two-dimensional phased arrays is summarized.The importance of the wideband and the wide-angle scanning characteristics for satellite communication is discussed.Issues like grating lobe avoidance,active reflection coefficient suppression and gain fluctuation reduction are emphasized in this review.Besides,techniques to address these issues and methods to realize the wideband wide-angle scanning phased array are reviewed.
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.
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 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support by the Advanced Integrated Optoelectronics Facility at Tianjin University
文摘Metasurfaces composed of two-dimensional nanopillar arrays can manipulate light fields in desirable ways and exhibit the unique advantage of beam steering.Here,we experimentally demonstrate a metasurface-based wide-angle broadband all-dielectric blazed grating with an extreme incident angle of up to 80°,which is achieved by optimizing the wide-angle phase shifts and transmissivities of the unit cells.It exhibits a maximum diffraction efficiency of 72%and a high average efficiency of 64%over a wide range of incident angles from−80° to 45° at 1.55μm.Moreover,the proposed grating has a broad bandwidth of 200 nm(1.45-1.65μm),and average efficiencies of more than 50%can be achieved experimentally over the same incidence angles.Our results may pave the way for the creation of novel and efficient flat optical devices for wavefront control.
基金supported by Sichuan Science and Technology Programs(2022NSFSC0547,2022ZYD0109)the 2020 Open Foundation of Key Laboratory of Cognitive Radio and Information Processing,Ministry of Education(Guilin University of Electronic Technology)(CRKL200201).
文摘In this paper, the reactive splitter network and meta-surface are proposed to radiate the wide-beam isolated element pattern and suppress mutual coupling (MC) of the low-profile phased array with the triangular lattice, respectively. Thus, broadband wide-angle impedance matching (WAIM) is imple-mented to promote two-dimensional (2D) wide scanning. For the isolated element, to radiate the wide-beam patterns approximat-ing to the cosine form, two identical slots backed on one sub-strate integrated cavity are excited by the feeding network con-sisting of a reactive splitter and two striplines connected with splitter output paths. For adjacent elements staggered with each other, with the metasurface superstrate, the even-mode cou-pling voltages on the reactive splitter are cancelled out, yielding reduced MC. With the suppression of MC and the compensa-tion of isolated element patterns, WAIM is realized to achieve 2D wide-angle beam steering up to ± 65° in E-plane, ± 45° in H-plane and ± 60° in D-plane from 4.9 GHz to 5.85 GHz.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2023YFB3811400 and 2022YFB3806000)the National Natural Science Foundation of China(Grant No.12074314)+1 种基金the Science and Technology New Star Program of Shaanxi Province,China(Grant No.2023KJXX-148)the Fundamental Research Funds for the Central Universities。
文摘The emergent metagrating,with its unique and flexible beam shaping capabilities,offers new paths to efficient modulation of acoustic waves.In this work,an acoustic metagrating is demonstrated for high-efficiency and wide-angle anomalous refraction.It is shown that the normal reflection and transmission can be totally suppressed by properly modulating the amplitude and phase characteristics of the metagrating supercells for high-efficiency anomalous refraction.The anomalous refraction behavior is achieved in the wide range of incident angles from 28°to 78°,and the efficiency of-1st order diffraction is higher than 90%by finely designing the metagrating structure.The anomalous refraction behaviors are verified experimentally at incidence angle of 28°,45°,and 78°,respectively.The demonstrated metagrating is anticipated to possess efficient wide-angle composite wavefront engineering applications in such fields as communications.
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.
基金Project supported by the National Key Research&Development Program of China(Grant Nos.2019YFA0308600 and 2020YFA0309000)the National Natural Science Foundation of China(Grant Nos.92365302,92065201,22325203,92265105,12074247,12174252,52102336)+2 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB28000000)the Science and Technology Commission of Shanghai Municipality(Grant Nos.2019SHZDZX01,19JC1412701,20QA1405100,24LZ1401000,LZPY2024-04)financial support from the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0302500)。
文摘Manipulating and braiding Majorana zero modes(MZM)are a critical step toward realizing topological quantum computing.The primary challenge is controlling the vortex,which hosts the MZM,within a superconducting film in a spatially precise manner.To address this,we developed a magnetic force-based vortex control technology using the STM system with a self-designed four-electrode piezo-scanner tube and investigated vortex manipulation on the NbSe_(2) superconducting film.We employed ferromagnetic tips to control the movement of vortex array induced by the tip's remanent magnetism.A magnetic core solenoid device was integrated into the STM system and a strong magnetic tip demagnetization technique was developed,providing a viable technical solution for further enabling single vortex manipulation.
基金supported by the National Natural Science Foundation of China(No.62135005)National Key Research and Development Program of China(No.2022YFA1206300)+4 种基金Guangdong Basic and Applied Basic Research Foundation(No.2021B1515020046)the Open Project Program of Wuhan National Laboratory for Optoelectronics(No.2020WNLOKF021)China National Postdoctoral Program for Innovative Talents(No.BX20220133)China Postdoctoral Science Foundation(No.2022M721342)the Outstanding Innovative Talents Cultivation Funded Programs for Doctoral Students of Jinan University(No.2022CXB012)。
文摘Mitochondria play a crucial role in the physiological functions and energy metabolism of neurons,which can help in the understanding of complex biochemical reactions associated with various neurodegenerative diseases.Neurons,being highly differentiated terminal cells,require a greater number of mitochondria than ordinary cells to generate significant amounts of ATP,which is necessary for the growth of differentiated neuronal structures like axons and dendrites and the transmission of electrical signals along neuronal axons.Advancements in imaging technology,electrophysiology,and fluorescence targeting labeling have facilitated the study of mitochondrial movements in neurons and axons.However,disordered mitochondrial movements can hinder their analysis and characterization.Thus,it becomes necessary to artificially control their transport.Here,we demonstrate the utilization of scanning optical tweezers(SOTs)on the stable trapping and precise transport of soma or axon of neurons and enable.The presented method provides an optical approach to the control of mitochondria or other organelles in complex and variable biological environment.
基金supported by the National Natural Science Foundation of China(Grant No.82302173).
文摘Background:Contrast-enhanced magnetic resonance neurography(ceMRN)can enhance brachial plexus visualization and quality of imaging.However,the interval between contrast injection and scanning that provides the highest-quality images is not known.Methods:Fifteen patients underwent brachial plexus imaging using the 3D T2-NerveView sequence with a scanning duration of 5 min.A consecutive six-phase scan was initiated immediately at the start of contrast agent injection.Subsequently,all patients'images were classified into six groups according to the phases:group A(phase 1,delay 0 min),group B(phase 2,delay 5 min),group C(phase 3,delay 10 min),group D(phase 4,delay 15 min),group E(phase 5,delay 20 min),and group F(phase 6,delay 25 min).The image quality in each group was assessed based on nerve signal(signalnerve),muscle signal(signalmuscle),lymph node signal(signallymph node),background noise(BN),signal-to-noise ratio(SNR),contrast-to-noise ratio(CNR),and subjective score.Results:Signalnerve,signalmuscle,BN,and SNR did not significantly differ among the six groups(p>0.05).However,significant differences(p<0.05)were observed in signallymph node(F=16.067),CNR(F=9.495),and subjective score(χ^(2)=23.586).As the scanning delay increased,signallymph node intensity gradually increased whereas the CNR gradually decreased.The subjective score was significantly higher in groups B(4.830.24),C(4.900.21),D(4.870.30),E(4.830.31),and F(4.830.31)than in group A(4.470.30).Conclusion:We recommend performing brachial plexus ceMRN 5 min after contrast injection.With this delay,the brachial plexus can be visualized optimally with minimal interference from background signals.
基金supported by ZTE Industry-University-Institute Cooperation Funds under Grant No.HC-CN-20220719005。
文摘In this paper,a dual-polarized antenna operating at 3.5 GHz is presented with 2D beam-scanning performance.The steerable beam is realized based on a 2×2 active reflective metasurface.The active metasurface is composed of folded annular rings and cross dipoles embedded with voltage-controlled varactor diodes.By tuning the capacitance values of the varactors,the reflective phase of the metasurface is reconfigured to tilt the main beam.To verify the scanning performance,a prototype is fabricated and measured.At 3.5 GHz,the measured scanning ranges are from-25°to 29°and-27°to 29°in the XOZ and YOZ planes,respectively.
基金financially supported by China National Postdoctoral Program for Innovative Talents(BX20230269)National Key R&D Program of China(2022YFB4600800)Fundamental Research Funds for The Central Universities(2042024kf0015).
文摘Welding quality of electron beam welded joint is usually susceptible to the stability of keyhole during welding process.The more stable the keyhole,the better the welding quality.To reveal the evolution mechanism of keyhole and welding quality of the electron beam welded joint of magnesium-gadolinium alloy under different scanning path,numerical simulation was conducted for the changes in morphology of keyhole and liquid flow in molten pool.The magnesium-gadolinium alloy was welded by electron beam in vacuum with two different scanning paths,sinusoid path and cochleoid path,indicating the identical heat input,welding speed,and focusing state.The stability of keyhole was mainly related to the frequency of keyhole collapse.When the sinusoid scanning path was adopted,the fluids both inside the molten pool and at keyhole wall were disorder,corresponding to the numerous independent vortices and dramatically chaotic flows at their junctions.The maximum velocity of fluids ranged from 0.79 m/s to 1.02 m/s.The average and maximum depth of keyhole were 3.48 mm and 4.51 mm,respectively,meaning that the keyhole collapsed frequently.As the scanning path was changed into cochleoid mode,the electron beam scanned in a homogeneous manner without abrupt change in direction and speed like sinusoid path at its peaks and troughs.The maximum velocity of fluids was more uniform without drastic variation,ranging from 0.90 m/s to 1.01 m/s.The average and maximum depth of keyhole were decreased to 3.30 mm and 4.05 mm,respectively,indicating the more stable keyhole and alleviated collapse.Both the actual in-situ capture of molten pool signature and porosity inside the weld corresponded to the analysis of the change in keyhole stability.
