AIM:To describe the optical coherence tomography(OCT)features in the fellow eyes of individuals with full-thickness macular holes(FTMHs).METHODS:This multicenter retrospective study included observational and validati...AIM:To describe the optical coherence tomography(OCT)features in the fellow eyes of individuals with full-thickness macular holes(FTMHs).METHODS:This multicenter retrospective study included observational and validation groups,incorporating fellow eyes of patients diagnosed with idiopathic FTMH.OCT images were categorized according to International Vitreomacular Traction Study(IVTS)and Gass classification.Age-and sex-related cataract patients were served as control groups.Vertical and horizontal OCT images were chosen for further measurement.OCT parameters including foveal floor width(FFW),central foveal thickness(CFT)and FFW/CFT ratio were assessed and compared between observational and control groups and were validated by validation group.Receiver operating characteristic(ROC)curves were plotted for OCT parameters in identifying macular holes(MHs).RESULTS:A total of 73 patients were included in the observational group,comprising 51 females and 22 males,with an average age of 65.5±7.3y and an axial length of 23.9±0.8 mm.The validated group consisted of 47 patients,including 31 females and 16 males,with an average age of 65.0±7.4y and an average axial length of 23.6±0.8 mm.In the observational group,16.4%of the fellow eyes associated with FTMHs also exhibited MHs,while in the validated group,this prevalence was 12.7%.The 45.2%in the observational group and 44.6%in validated group of these fellow eyes displayed abnormalities including vitreomacular adhesion(VMA),vitreomacular traction(VMT),and MHs.Statistically significant differences were observed in FFW,CFT,and FFW/CFT ratio between control and observational group,as well as validated group(P<0.01),no matter in the vertical or horizontal layer.ROC curves revealed the area under the curve(AUC)for FFW and the FFW/CFT ratio was 0.85 and 0.90,respectively.CONCLUSION:In the case of unilateral idiopathic MHs,it was important to carefully monitor the condition of the fellow eye.The FFW and FFW/CFT ratio may be good metrics for predicting MHs.展开更多
The prediction of the rolling force and thickness ratio plays an important role in the development and application of bimetallic composite plates.To analyze the rolling force of the bimetallic composite plate more acc...The prediction of the rolling force and thickness ratio plays an important role in the development and application of bimetallic composite plates.To analyze the rolling force of the bimetallic composite plate more accurately,a novel hypothesis based on Orowan's theory was proposed.The variation in the thickness of each differential element at different positions was considered to establish the analytical model.According to the characteristics of bimetallic composite plate rolling,the rolling deformation can be divided into forward and backward slip zones.The initial thickness ratio after rolling was predetermined by the thickness ratio before rolling;the rolling force balance of the upper and lower rollers was considered the convergence condition;and the final thickness ratio of the bimetallic composite plate was obtained by iterative calculation.The calculation results of the analytical model were compared with the measured and simulated data.The results showed that the errors in the calculation of the rolling force and thickness ratio were both less than 10%.The analytical model has high precision,meets engineering requirements,and has important reference significance for rolling process optimization and thickness ratio prediction.展开更多
Based on the volume constancy with equal flow-per-second and elastic sheet stability theory, a coupling relationship among lateral thickness difference, width-to-thickness ratio of cold rolling strip steel under ideal...Based on the volume constancy with equal flow-per-second and elastic sheet stability theory, a coupling relationship among lateral thickness difference, width-to-thickness ratio of cold rolling strip steel under ideal and actual working conditions, and shape is concluded according to the comprehensive influence principle of various factors on the critical instable shape analyzed in-depth. Firstly, the influence model under actual working condition is developed by referring to the basic relationship between lateral thickness difference and shape under ideal condition. The test results prove that for thin strips with thickness below 0.3 mm, their lateral thickness differences have significant effect on the shape. After then, the combined influence of lateral thickness difference and width-to-thickness ratio on the critical instable shape is concluded according to the elastic sheet stability model, with the synthetic effect of these three factors analyzed. Test data indicate that for cold rolling strip steel with width-to-thickness ratio above 3 000, the critical instability stress difference decreases significantly. Actual measurements are conducted on the lateral thickness differences of two rolls of typical strip manufactured by a sixhigh cold mill, with the influence law of lateral thickness variation and width-to-thickness ratio comprehensively investigated. It is demonstrated that during the production of ultrathin strip steel with different width-to-thickness ratios, the loading roll shapes should be fine adjusted according to the lateral thickness difference of input strips.Therefore, the variation of lateral thickness difference of output strips can meet the requirement of shape stability,so as to obtain fine shape.展开更多
In the Southeast Margin of the Tibetan Plateau, low-velocity sedimentary layers that would significantly affect the accuracy of the H-κ stacking of receiver functions are widely distributed.In this study, we use tele...In the Southeast Margin of the Tibetan Plateau, low-velocity sedimentary layers that would significantly affect the accuracy of the H-κ stacking of receiver functions are widely distributed.In this study, we use teleseismic waveform data of 475 events from 97 temporary broadband seismometers deployed by ChinArray Phase I to obtain crustal thicknesses and Poisson's ratios within the Chuxiong-Simao Basin and adjacent area, employing an improved method in which the receiver functions are processed through a resonance-removal filter, and the H-κ stacking is time-corrected.Results show that the crustal thickness ranges from 30 to 55 km in the study area, reaching its thickest value in the northwest and thinning toward southwest, southeast and northeast.The apparent variation of crustal thickness around the Red River Fault supports the view of southeastern escape of the Tibetan Plateau.Relatively thin crustal thickness in the zone between Chuxiong City and the Red River Fault indicates possible uplift of mantle in this area.The positive correlation between crustal thickness and Poisson's ratio is likely to be related to lower crust thickening.Comparison of results obtained from different methods shows that the improved method used in our study can effectively remove the reverberation effect of sedimentary layers.展开更多
Shanxi Graben is in the middle part of the North China Craton, from south to north. With the teleseismic data recorded by Regional Seismograph Networks and the temporary ZBnet-W Seismic Array around east part of Shanx...Shanxi Graben is in the middle part of the North China Craton, from south to north. With the teleseismic data recorded by Regional Seismograph Networks and the temporary ZBnet-W Seismic Array around east part of Shanxi Graben, we measured the crustal thickness and Vp/Vs ratio beneath each station using the H-K stack of receiver functions. The observed crustal thickness shows obvious lateral variation, increasing gradually from east to west in the Shanxi Graben. Beneath the Shanxi Graben the crust is relatively thicker than both sides of the south and the north. In addition, the Vp/Vs ratio in the north of study zone is higher than that in the south. The highest Vp/Vs ratio exists in the crust of the Xinding basin and the Datong basin. Our study also suggests that high velocity ratio might result from the strong activities of the magmation and volcanism.展开更多
In this study, CrN/Cr2O3 double-layered coatings with various thickness ratios of CrN vs Cr2O3 layer were prepared by arc ion plating technology. The influences of the thickness ratio of CrN vs Cr2O3 layer on the micr...In this study, CrN/Cr2O3 double-layered coatings with various thickness ratios of CrN vs Cr2O3 layer were prepared by arc ion plating technology. The influences of the thickness ratio of CrN vs Cr2O3 layer on the microstructural characteristics as well as the mechanical and tribological properties of the CrN/Cr2O3 doublelayered coatings were investigated. The corresponding mechanisms were also discussed. The results indicated that the insertion of CrN layer between the Cr2O3 layer and substrate can effectively decrease the internal stress level of the coating. With increasing the thickness ratio of CrN vs Cr2O3 layer, the surface roughness of double-layered coatings decreased gradually, which had a certain influence on the friction coefficient. In addition, the microhardness also declined gradually, the adhesive strength almost increased linearly, whereas the wear rate declined firstly and then increased slightly. As the thickness ratio was 2：1, the double-layered coating exhibited the best wear resistance.展开更多
The main objective of the present investigation is to study the vibration of visco-elastic parallelogram plate whose thickness varies parabolically. It is assumed that the plate is clamped on all the four edges and th...The main objective of the present investigation is to study the vibration of visco-elastic parallelogram plate whose thickness varies parabolically. It is assumed that the plate is clamped on all the four edges and that the thickness varies parabolically in one direction i.e. along length of the plate. Rayleigh-Ritz technique has been used to determine the frequency equation. A two terms deflection function has been used as a solution. For visco-elastic, the basic elastic and viscous elements are combined. We have taken Kelvin model for visco-elasticity that is the combination of the elastic and viscous elements in parallel. Here the elastic element means the spring and the viscous element means the dashpot. The assumption of small deflection and linear visco-elastic properties of “Kelvin” type are taken. We have calculated time period and deflection at various points for different values of skew angles, aspect ratio and taper constant, for the first two modes of vibration. Results are supported by tables. Alloy “Duralumin” is considered for all the material constants used in numerical展开更多
The squeeze cast technology is only applicable, at present, to the castings with a ratio of height to thickness less than 3.5. Researching the squeeze cast technology for castings with a large ratio of height to thick...The squeeze cast technology is only applicable, at present, to the castings with a ratio of height to thickness less than 3.5. Researching the squeeze cast technology for castings with a large ratio of height to thickness will broaden the applicable range of the advanced casting technology. This paper describes a study of the temperature distribution during solidification for castings with a ratio of height to thickness of 7 by the methods of experiment and computer simulation. The shrinkage porosity distribution in the castings and the mechanical properties of the castings were also researched. The experimental and simulated results show that increasing squeeze force, or enhancing mold temperature, cannot reduce the shrinkage porosities in the castings. When castings solidify in a sequential manner and the squeeze force effectively acts on the surface of the liquid metal, the shrinkage porosities in the castings are eliminated and mechanical properties are clearly improved.展开更多
The present paper investigates the welding forming,microstructure and shear tensile test of lap joints with large thickness ratio which were fabricated by laser screw welding(LSW)and resistant spot welding(RSW).The co...The present paper investigates the welding forming,microstructure and shear tensile test of lap joints with large thickness ratio which were fabricated by laser screw welding(LSW)and resistant spot welding(RSW).The comparison was conducted on two kinds of lap joints,galvanized sheet and hot pressed steel(GS-HPS),galvanized sheet and high strength steel(GS-HS).The microstructure and fracture morphology were analyzed by optical microscope.It was demonstrated that with large thickness ratio the sound lap joint of GS-HS could be obtained by LSW regardless of the irradiation of laser beam from thick metal to sheet or otherwise,and the morphology shows it is better when the laser is irradiated on the thick metal.Nevertheless,when the laser beam was applied on thick metal of HPS,blind hole or blowhole was formed in the center of joint,which is attributed to the shrinkage during solidification of the molten pool.Small pores or dispersed porosity appeared on the faying face of the joint without predetermined gap which provides the degassing.However,the increase of predetermined gap could reduce the shear strength and nugget size.Two kinds of joints made by LSW have superior shear strength than those made by RSW when the laser were applied on galvanized sheet.展开更多
As one of the advanced and efficient means of joining,the clinching process is capable of joining sheets with different materials or different sheet thicknesses.In this article,a novel modified clinching process,i.e.,...As one of the advanced and efficient means of joining,the clinching process is capable of joining sheets with different materials or different sheet thicknesses.In this article,a novel modified clinching process,i.e.,the dieless clinching process,was executed to join AA6061 aluminum alloy with sheet thicknesses of 1.5,2.0,2.5 and 3.0 mm according to different sheet stack-ups.The geometrical characteristics,microhardness distribution,failure behavior,static strength,absorbed energy and instantaneous stiffness of the novel dieless joint were gotten and investigated.The results indicated that the sheet thickness ratio has a notable effect on the failure behavior and mechanical properties of the novel dieless clinched joint,and a relatively large sheet thickness ratio can improve the joint performance when joining sheets with different sheet thicknesses.展开更多
BACKGROUND The hemoglobin-to-red cell distribution width ratio(HRR)is a recently intro-duced,easily accessible marker that provides insights into inflammation and the tumor vascular microenvironment.It has been sugges...BACKGROUND The hemoglobin-to-red cell distribution width ratio(HRR)is a recently intro-duced,easily accessible marker that provides insights into inflammation and the tumor vascular microenvironment.It has been suggested to have prognostic value for overall survival in various types of cancer,including urothelial carcinoma,lung cancer,and hepatocellular carcinoma.It has not yet been sufficiently invest-igated in colorectal cancers(CRC).AIM To investigate the prognostic significance of the HRR and other inflammation-based hematological markers in patients with metastatic CRC.Additionally,the study evaluated the impact of surgical interventions,particularly metastasectomy,and multiple clinical and laboratory parameters on overall survival.By iden-tifying low-cost,accessible prognostic indicators,this research seeks to support clinicians in optimizing treatment strategies and risk stratification for patients with CRC.METHODS In this retrospective study,patients diagnosed with CRC between January 2020 and December 2024 were analyzed.The impact of HRR in conjunction with inflammatory markers and a total of 22 different clinical and laboratory para-meters on overall survival were evaluated using univariate Cox regression and a multivariate model.Survival curves were visualized using Kaplan-Meier analysis.RESULTS A total of 155 patients with CRC were included in the study.The median age was 60 years,and 61.9%presented with de novo metastasis.In the receiver operating characteristic curve and area under the curve analysis performed to determine the optimal cutoff,the values were found to be 6.10 for carcinoembryonic antigen(CEA)(P=0.036),18.85 for platelet-to-red cell distribution width ratio(P=0.028),and 10.87 for platelet distribution width-to-lymphocyte ratio(P=0.028).For neutrophil-to-lymphocyte ratio,systemic immune-inflammation index(SII),platelet-to-lymphocyte ratio(PLR),monocyte-to-lymphocyte ratio,HRR,and carbohydrate antigen 19-9,an optimal cutoff could not be determined using the receiver operating characteristic-area under the curve analysis.Therefore,the median values were adopted as the cutoffs(3.09,835.96,177.50,0.380,0.824,and 21.6,respectively).Univariate analysis identified male gender(P=0.045),being under 65 years of age(P=0.001),history of metastas-ectomy(P=0.001),low serum CEA level(P=0.010),low PLR(P=0.024),low SII(P=0.010),and high HRR(P=0.025)as favorable prognostic factors for overall survival.In the multivariate model,being under 65 years of age[hazard ratio(HR)=1.59,95%confidence interval(CI):1.06-2.39,P=0.025],metastasectomy(HR=0.49,95%CI:0.29-0.85,P=0.011),CEA(HR=1.51,95%CI:1.0-2.28,P=0.048),and PLR(HR=1.63,95%CI:1.09-2.44,P=0.018)emerged as independent prognostic factors for overall survival,whereas gender,SII,and HRR did not retain statistical significance.CONCLUSION In conclusion,low HRR alone was a prognostic indicator.However,when modelled with other inflammatory and clinical parameters,it did not provide a sufficiently strong marker feature.展开更多
AIM:To assess and compare the utility of neutrophil-to-lymphocyte ratio(NLR),platelet-to-lymphocyte ratio(PLR),systemic inflammation index(SII),and red blood cell distribution width(RDW)as potential biomarkers to pred...AIM:To assess and compare the utility of neutrophil-to-lymphocyte ratio(NLR),platelet-to-lymphocyte ratio(PLR),systemic inflammation index(SII),and red blood cell distribution width(RDW)as potential biomarkers to predict the severity of diabetic retinopathy(DR)in the United States population.METHODS:The observational study enlisted patients diagnosed with DR from the National Health and Nutrition Examination Survey(NHANES)database,spanning the period from 2005 to 2008.The severity of DR was defined according to Early Treatment for Diabetic Retinopathy Study(ETDRs).The effect of NLR,PLR,SII,and RDW on proliferative diabetic retinopathy(PDR)were explored using multivariable logistic regression analysis model.Subgroup analysis and restricted cubic splines(RCS)were conducted to assess the robustness of the correlations across subgroups and to explore nonlinear relationships between four indices and PDR.The receiver operating characteristic(ROC)analysis was employed for the purpose of assessing and evaluating the predictive efficacy of NLR,PLR,SII,and RDW in determining the severity of DR.RESULTS:After adjusting for other confounders(age,gender,race,body mass index,diabetes duration,and HbA1c)in multivariable analysis,a unit increase of PLR×0.1,SII×0.01,and RDW would raise the risk for PDR by 15.6%,22.2%,and 33%,respectively.Particularly,there was a 2.208-fold greater risk of PDR in individuals with an elevated NLR(OR=2.208,95%CI,1.348-3.617,P<0.001).RCS analyses showed positive relationships of four indices and PDR after segmented regression based on their own turning points.The results of ROC analysis revealed that PLR+RDW[area under the curve(AUC)=0.772,95%CI:0.669-0.874]had the best predictive value for PDR,compared with NLR+PLR+SII(AUC=0.697,95%CI:0.570-0.825)or RDW alone(AUC=0.736,95%CI:0.646-0.826).CONCLUSION:The combination of RDW and NLR demonstrates a promising ability to predict the severity of DR across the United States population,and it could be promisingly used in clinics for monitoring the progress of DR.展开更多
Reliable thickness of sedimentary layers is essential for seismic hazard assessment in active fault zones, especially in regions prone to strong earthquakes. This study analyzed the seismic ambient noise data recorded...Reliable thickness of sedimentary layers is essential for seismic hazard assessment in active fault zones, especially in regions prone to strong earthquakes. This study analyzed the seismic ambient noise data recorded by 60 short-period seismic stations deployed at the Jishishan earthquake source and adjacent areas. The base-order resonance frequencies of sedimentary layers beneath the stations were determined using the horizontal-to-vertical spectral ratio method on ambient noise with diff erent frequencies. Then, a resonance-thickness formula was applied to estimate the sedimentary layer thickness at each station. Finally, the entire regional sediment thickness was obtained via interpolation. The thickness of the sedimentary layer beneath each station was estimated using the equation of the relationship between resonance frequency and sedimentary layer thickness, and fi nally, the distribution of sedimentary layer thickness in the whole region was obtained by interpolation. Results reveal notable spatial variations in sediment thickness in the source and adjacent areas. The shallow sedimentary layer in the source area is relatively thick at approximately 100 m, whereas that in Liugou Village, which is the most severely damaged area, is approximately 150-180 m. In the western region, specifically along the western edge of the Jishishan Mountain rupture and the Pourouliuhe-Cheunhua Nanshan rupture zone, the shallow sedimentary layer is approximately 30-60 m. A comparison between the distribution of seismic secondary hazards and sedimentary layer thickness highlights a strong correlation between these hazards and the amplifi cation eff ects of seismic waves. In regions with thicker sedimentary layers, ground shaking is signifi cantly amplifi ed, resulting in more serious seismic secondary hazards. In addition, the study confi rmed that secondary hazards, such as landslides and liquefaction, were more prevalent in regions with thicker sedimentary layers. These fi ndings provide an important reference for post-earthquake reconstruction, seismic risk assessment, and the development of regional disaster prevention and mitigation strategies..展开更多
Determining the evolutionary history of the Permian-Triassic Kunlun-Qaidam Continental Arc is essential to understanding the subduction and closure processes of the South Kunlun Ocean.In this paper,we utilize(La/Yb)N ...Determining the evolutionary history of the Permian-Triassic Kunlun-Qaidam Continental Arc is essential to understanding the subduction and closure processes of the South Kunlun Ocean.In this paper,we utilize(La/Yb)N ratios collected from a fi ltered geochemical dataset on Permian to Triassic calc-alkaline rocks(55 wt%–68 wt%SiO_(2))and plutonic rocks within the Kunlun-Qaidam Continental Arc to reconstruct the spatiotemporal variation of the relative crustal thickness.Combined with known geologic observations,we discuss the subduction-accretionary tectonics of the South Kunlun Ocean and the topographic evolution of the Kunlun-Qaidam Continental Arc.Two episodes of crustal thickening and thinning were revealed.The reconstructed thickness reveals two crustal thickening and thinning events for the Kunlun-Qaidam Continental Arc from ca.270 to 210 Ma.The southern sector of the Kunlun-Qaidam Continental Arc is about 7 km thicker than the northern portion,with a maximum thickness of about 55 km at ca.270 and 230 Ma.The ca.270 and 230 Ma crustal thickening events coincide with renewed northward subduction of the South Kunlun Ocean plate and ocean closure,respectively,whereas the ca.270‒240 Ma and ca.230‒210 Ma crustal thinning events may refl ect slab break-off of the oceanic plate and lithospheric collapse during the post-collision extension,respectively.展开更多
The Xing’an Mongolian Orogenic Belt(XMOB) and the northern margin of North China Craton(NCC) have undergone multistage tectonic superimposition and the tectonic evolution is extremely complicated. We collect the tele...The Xing’an Mongolian Orogenic Belt(XMOB) and the northern margin of North China Craton(NCC) have undergone multistage tectonic superimposition and the tectonic evolution is extremely complicated. We collect the teleseismic data of 44 temporary broadband seismic stations deployed in the XMOB and the northern margin of NCC to calculate the P wave receiver functions. The crustal thickness and average crustal ratio as well as the Poisson’s ratios beneath 33 stations are estimated using the H-κ stacking method. The results show:(1) the crustal thickness of the study area ranges from 38.7 to 42.7 km, with an average thickness of 41.2 km. There is a great difference in crustal thickness on both sides of Solonker suture zone. The characteristics of crustal thickness support the geodynamic model that the Paleo-Asian Ocean subducted and closed at the Solonker suture zone.(2) The Poisson’s ratios in the study area are low, ranging from 0.215 to 0.277, with an average value of 0.243, suggesting that the rock composition of the area is dominated by felsic-acid rocks.(3) There exists a negative correlation between the Poisson’s ratio and the crustal thickness. Combined with the lower values of Poisson’s ratio, we speculate that the delamination is the major mechanism in crustal extension and thinning in the study area.展开更多
In order to optimize the laser ablation performance of a micro-thruster with 1U dimensions,which employs a micro semiconductor laser,the impacts of pulse width and glycidyl azide polymer(GAP)thickness on thrust perfor...In order to optimize the laser ablation performance of a micro-thruster with 1U dimensions,which employs a micro semiconductor laser,the impacts of pulse width and glycidyl azide polymer(GAP)thickness on thrust performance were researched.The results showed that with a GAP thickness of 200μm,the single-pulse impulse(I)increased gradually with the increase in the laser pulse width from 50 to 800μs,while the specific impulse(I_(sp)),impulse coupling coefficient(Cm)and ablation efficiency(η)all reached optimal values with a 200μs pulse width.It is worth noting that the optimal pulse width is identical to the ignition delay time.Both Cmandηpeaked with a pulse width of 200μs,reaching 242.22μN W^(-1)and 35.4%,respectively.With the increase in GAP thickness,I and Cmincreased gradually.GAP of different thicknesses corresponded to different optimal laser pulse widths.Under a certain laser pulse width,the optimal GAP thickness should be the most vertical thickness of the ablation pit,and the various propulsion performance parameters at this time were also optimal.With the current laser parameters,the optimal GAP thickness was approximately 150μm,I_(sp)was approximately 322.22 s,andηwas approximately 34.94%.展开更多
The yield ratios of neutron-proton(R(n/p))and^(3)H-^(3)He(R(^(3)H∕^(3)He))with reduced rapidity from 0 to 0.5 were simulated at 50 MeV/u even-even ^(36−56)Ca+^(40)Ca,even-even ^(48−78)Ni+^(58)Ni,and ^(100−139)Sn(ever...The yield ratios of neutron-proton(R(n/p))and^(3)H-^(3)He(R(^(3)H∕^(3)He))with reduced rapidity from 0 to 0.5 were simulated at 50 MeV/u even-even ^(36−56)Ca+^(40)Ca,even-even ^(48−78)Ni+^(58)Ni,and ^(100−139)Sn(every third isotopes)+112 Sn for full reduced impact parameters using the isospin-dependent quantum molecular dynamics(IQMD)model.The neutron and proton density distributions and root-mean-square radii of the reaction systems were obtained using the Skyrme-Hartree-Fock model,which was used for the phase space initialization of the projectile and target in IQMD.We defined the unified neutron skin thickness asΔRnp=<r^(2)>^(1∕2) n−<r^(2)>^(1∕2)p,which was negative for neutron-deficient nuclei.The unifiedΔRnp values for nuclei with the same relative neutron excess from different isotopic chains were nearly equal,except for extreme neutron-rich isotopes,which is a type of scaling behavior.The yield ratios of the three isotopic chain-induced reactions,which depended on the reduced impact parameter and unified neutron skin thickness,were studied.The results showed that both R(n/p)and R(^(3)H∕^(3)He)decreased with a reduced impact parameter for extreme neutron-deficient isotopes;however,they increased with reduced impact parameters for extreme neutron-rich isotopes,and increased with theΔRnp of the projectiles for all reduced impact parameters.In addition,a scaling phenomenon was observed betweenΔR np and the yield ratios in peripheral colli-sions from different isotopic chain projectiles(except for extreme neutron-rich isotopes).Thus,R(n/p)and R(^(3)H∕^(3)He)from peripheral collisions were suggested as experimental probes for extracting the neutron or proton skin thicknesses of non-extreme neutron-rich nuclei from different isotopic chains.展开更多
Silicon carbide ceramics with different thicknesses/diameter ratios were prepared by using ultra-fine silicon carbide powder with the sintering additives of 1.0 wt% boron and 1.5 wt% carbon. The influence of thickness...Silicon carbide ceramics with different thicknesses/diameter ratios were prepared by using ultra-fine silicon carbide powder with the sintering additives of 1.0 wt% boron and 1.5 wt% carbon. The influence of thickness/diameter ratio on the microstructure and density of SiC ceramics was investigated in detail. The experimental results show that the addition of boron and carbon sintering aids can promote the densification process of SiC ceramic, leading to the low sintering temperature and improve mechanical properties. At 1950 ℃, SiC ceramic with a density of 99% exhibits Young's modulus, hardness, and flexural strength of 476 MPa, 28.3 GPa, and 334 MPa, respectively. It is found that long holding time has a positive effect on the uniformity of the microstructure and density distribution of SiC ceramics with large thickness/diameter ratios. Additionally, the sintering additive of boron can solid-solve into SiC, and then facilitate the phase transformation of SiC to form 6H-SiC and 4H-SiC composite ceramics.展开更多
Three-dimensional direct numerical simulations of the wake flow downstream of a near-wall circular cylinder at different gap ratios and boundary layer thicknesses are carried out by using the iterative immersed bounda...Three-dimensional direct numerical simulations of the wake flow downstream of a near-wall circular cylinder at different gap ratios and boundary layer thicknesses are carried out by using the iterative immersed boundary method.The non-dimensional gap between the cylinder and the wall,G/D=0.2,0.6 and 1.0,the non-dimensional boundary layer thickness,δ/D=0.0,0.7 and 1.6,the Reynolds number,Re=350,and the aspect ratio of the cylinder,L/D=25are adopted.High-resolution visualizations of the complex vortex structures at differentδ/D and G/D are presented.The transition of the streamwise vortex mode,the combined effects ofδ/D and G/D on the flow statistics,the pressure and shear stress distribution and the hydrodynamic forces are analyzed.Results show that with decreasing G/D and increasingδ/D,the gap flow and its vortex-shedding are significantly weakened,together with an elongated wake and an enlarged low-velocity area near the wall,leading to the wake mode transition from the two-sided to one-sided vortex-shedding.Different relative positions of the cylinder regarding the boundary layer alter the flow features of the shear layers.With an increase inδ/D,the front stagnation point shifts to the upper surface,and the distance between the flow divergence point and the maximum pressure position increases.The mean drag coefficient and r.m.s.values of drag and lift coefficients decrease with a decrease in G/D and an increase inδ/D,while the mean lift coefficient increases with decreasing G/D but decreases with increasingδ/D.展开更多
The present analysis demonstrates the thermal effect on vibrations of a symmetric, non-homoge- neous trapezoidal plate with parabolically varying thickness in both directions. The variation in Young’s modulus and mas...The present analysis demonstrates the thermal effect on vibrations of a symmetric, non-homoge- neous trapezoidal plate with parabolically varying thickness in both directions. The variation in Young’s modulus and mass density is the main cause for the occurrence of non-homogeneity in plate’s material. In this consideration, density varies linearly in one direction. The governing differential equations have been derived by Rayleigh-Ritz method in order to attain fundamental frequencies. With C-S-C-S boundary condition, a two term deflection function has been considered. The effect of structural parameters such as taper constants, thermal gradient, aspect ratio and non-homogeneity constant has been investigated for first two modes of vibration. The obtained numerical results have been presented in tabular and graphical form.展开更多
基金Supported by Jiangsu Provincial Medical Innovation Team(No.CXTDA2017039)the Soochow Scholar Project of Soochow University(No.R5122001).
文摘AIM:To describe the optical coherence tomography(OCT)features in the fellow eyes of individuals with full-thickness macular holes(FTMHs).METHODS:This multicenter retrospective study included observational and validation groups,incorporating fellow eyes of patients diagnosed with idiopathic FTMH.OCT images were categorized according to International Vitreomacular Traction Study(IVTS)and Gass classification.Age-and sex-related cataract patients were served as control groups.Vertical and horizontal OCT images were chosen for further measurement.OCT parameters including foveal floor width(FFW),central foveal thickness(CFT)and FFW/CFT ratio were assessed and compared between observational and control groups and were validated by validation group.Receiver operating characteristic(ROC)curves were plotted for OCT parameters in identifying macular holes(MHs).RESULTS:A total of 73 patients were included in the observational group,comprising 51 females and 22 males,with an average age of 65.5±7.3y and an axial length of 23.9±0.8 mm.The validated group consisted of 47 patients,including 31 females and 16 males,with an average age of 65.0±7.4y and an average axial length of 23.6±0.8 mm.In the observational group,16.4%of the fellow eyes associated with FTMHs also exhibited MHs,while in the validated group,this prevalence was 12.7%.The 45.2%in the observational group and 44.6%in validated group of these fellow eyes displayed abnormalities including vitreomacular adhesion(VMA),vitreomacular traction(VMT),and MHs.Statistically significant differences were observed in FFW,CFT,and FFW/CFT ratio between control and observational group,as well as validated group(P<0.01),no matter in the vertical or horizontal layer.ROC curves revealed the area under the curve(AUC)for FFW and the FFW/CFT ratio was 0.85 and 0.90,respectively.CONCLUSION:In the case of unilateral idiopathic MHs,it was important to carefully monitor the condition of the fellow eye.The FFW and FFW/CFT ratio may be good metrics for predicting MHs.
基金Supported by National Key Research and Development Program of China(Grant No.2018YFA0707300)Major Program of National Natural Science Foundation of China(Grant No.U22A20188)+1 种基金General Program of National Natural Science Foundation of China(Grant No.51974196)Postdoctoral Science Foundation of China(Grant No.201903D421047)。
文摘The prediction of the rolling force and thickness ratio plays an important role in the development and application of bimetallic composite plates.To analyze the rolling force of the bimetallic composite plate more accurately,a novel hypothesis based on Orowan's theory was proposed.The variation in the thickness of each differential element at different positions was considered to establish the analytical model.According to the characteristics of bimetallic composite plate rolling,the rolling deformation can be divided into forward and backward slip zones.The initial thickness ratio after rolling was predetermined by the thickness ratio before rolling;the rolling force balance of the upper and lower rollers was considered the convergence condition;and the final thickness ratio of the bimetallic composite plate was obtained by iterative calculation.The calculation results of the analytical model were compared with the measured and simulated data.The results showed that the errors in the calculation of the rolling force and thickness ratio were both less than 10%.The analytical model has high precision,meets engineering requirements,and has important reference significance for rolling process optimization and thickness ratio prediction.
基金the Special Research Fund for the National Major Science and Technology Achievement Transformation Project(No.2012GG01)the National Natural Science Foundation of China(No.51305387)the Provincial Natural Science Foundation of Hebei of China(No.E2015203103)
文摘Based on the volume constancy with equal flow-per-second and elastic sheet stability theory, a coupling relationship among lateral thickness difference, width-to-thickness ratio of cold rolling strip steel under ideal and actual working conditions, and shape is concluded according to the comprehensive influence principle of various factors on the critical instable shape analyzed in-depth. Firstly, the influence model under actual working condition is developed by referring to the basic relationship between lateral thickness difference and shape under ideal condition. The test results prove that for thin strips with thickness below 0.3 mm, their lateral thickness differences have significant effect on the shape. After then, the combined influence of lateral thickness difference and width-to-thickness ratio on the critical instable shape is concluded according to the elastic sheet stability model, with the synthetic effect of these three factors analyzed. Test data indicate that for cold rolling strip steel with width-to-thickness ratio above 3 000, the critical instability stress difference decreases significantly. Actual measurements are conducted on the lateral thickness differences of two rolls of typical strip manufactured by a sixhigh cold mill, with the influence law of lateral thickness variation and width-to-thickness ratio comprehensively investigated. It is demonstrated that during the production of ultrathin strip steel with different width-to-thickness ratios, the loading roll shapes should be fine adjusted according to the lateral thickness difference of input strips.Therefore, the variation of lateral thickness difference of output strips can meet the requirement of shape stability,so as to obtain fine shape.
基金supported by the National Natural Science Foundation of China (Project 41730212)the Basic Research Project of the Institute of Earthquake Forecasting, China Earthquake Administration (2017IES0102)
文摘In the Southeast Margin of the Tibetan Plateau, low-velocity sedimentary layers that would significantly affect the accuracy of the H-κ stacking of receiver functions are widely distributed.In this study, we use teleseismic waveform data of 475 events from 97 temporary broadband seismometers deployed by ChinArray Phase I to obtain crustal thicknesses and Poisson's ratios within the Chuxiong-Simao Basin and adjacent area, employing an improved method in which the receiver functions are processed through a resonance-removal filter, and the H-κ stacking is time-corrected.Results show that the crustal thickness ranges from 30 to 55 km in the study area, reaching its thickest value in the northwest and thinning toward southwest, southeast and northeast.The apparent variation of crustal thickness around the Red River Fault supports the view of southeastern escape of the Tibetan Plateau.Relatively thin crustal thickness in the zone between Chuxiong City and the Red River Fault indicates possible uplift of mantle in this area.The positive correlation between crustal thickness and Poisson's ratio is likely to be related to lower crust thickening.Comparison of results obtained from different methods shows that the improved method used in our study can effectively remove the reverberation effect of sedimentary layers.
基金supported by the National Natural Science Foundation of China(No.41230210)the Projects of International Cooperation and Exchanges from the Ministry of Science and Technology of China(Grant No.2010DFB20190)the Fundamental Research Funds for the Institute of Earthquake Science,China Earthquake Administration
文摘Shanxi Graben is in the middle part of the North China Craton, from south to north. With the teleseismic data recorded by Regional Seismograph Networks and the temporary ZBnet-W Seismic Array around east part of Shanxi Graben, we measured the crustal thickness and Vp/Vs ratio beneath each station using the H-K stack of receiver functions. The observed crustal thickness shows obvious lateral variation, increasing gradually from east to west in the Shanxi Graben. Beneath the Shanxi Graben the crust is relatively thicker than both sides of the south and the north. In addition, the Vp/Vs ratio in the north of study zone is higher than that in the south. The highest Vp/Vs ratio exists in the crust of the Xinding basin and the Datong basin. Our study also suggests that high velocity ratio might result from the strong activities of the magmation and volcanism.
基金the National Key Basic Research Program of China("973 Program",No.2012CB625100)the National Natural Science Foundation of China(No.51001106&No.51301181)the Doctoral Starting up Foundation of Liaoning Province Science and Technology Agency,China(No.20131118)
文摘In this study, CrN/Cr2O3 double-layered coatings with various thickness ratios of CrN vs Cr2O3 layer were prepared by arc ion plating technology. The influences of the thickness ratio of CrN vs Cr2O3 layer on the microstructural characteristics as well as the mechanical and tribological properties of the CrN/Cr2O3 doublelayered coatings were investigated. The corresponding mechanisms were also discussed. The results indicated that the insertion of CrN layer between the Cr2O3 layer and substrate can effectively decrease the internal stress level of the coating. With increasing the thickness ratio of CrN vs Cr2O3 layer, the surface roughness of double-layered coatings decreased gradually, which had a certain influence on the friction coefficient. In addition, the microhardness also declined gradually, the adhesive strength almost increased linearly, whereas the wear rate declined firstly and then increased slightly. As the thickness ratio was 2：1, the double-layered coating exhibited the best wear resistance.
文摘The main objective of the present investigation is to study the vibration of visco-elastic parallelogram plate whose thickness varies parabolically. It is assumed that the plate is clamped on all the four edges and that the thickness varies parabolically in one direction i.e. along length of the plate. Rayleigh-Ritz technique has been used to determine the frequency equation. A two terms deflection function has been used as a solution. For visco-elastic, the basic elastic and viscous elements are combined. We have taken Kelvin model for visco-elasticity that is the combination of the elastic and viscous elements in parallel. Here the elastic element means the spring and the viscous element means the dashpot. The assumption of small deflection and linear visco-elastic properties of “Kelvin” type are taken. We have calculated time period and deflection at various points for different values of skew angles, aspect ratio and taper constant, for the first two modes of vibration. Results are supported by tables. Alloy “Duralumin” is considered for all the material constants used in numerical
基金The research is supported by Nature Science Foundation ofChina, No.: 50275098
文摘The squeeze cast technology is only applicable, at present, to the castings with a ratio of height to thickness less than 3.5. Researching the squeeze cast technology for castings with a large ratio of height to thickness will broaden the applicable range of the advanced casting technology. This paper describes a study of the temperature distribution during solidification for castings with a ratio of height to thickness of 7 by the methods of experiment and computer simulation. The shrinkage porosity distribution in the castings and the mechanical properties of the castings were also researched. The experimental and simulated results show that increasing squeeze force, or enhancing mold temperature, cannot reduce the shrinkage porosities in the castings. When castings solidify in a sequential manner and the squeeze force effectively acts on the surface of the liquid metal, the shrinkage porosities in the castings are eliminated and mechanical properties are clearly improved.
文摘The present paper investigates the welding forming,microstructure and shear tensile test of lap joints with large thickness ratio which were fabricated by laser screw welding(LSW)and resistant spot welding(RSW).The comparison was conducted on two kinds of lap joints,galvanized sheet and hot pressed steel(GS-HPS),galvanized sheet and high strength steel(GS-HS).The microstructure and fracture morphology were analyzed by optical microscope.It was demonstrated that with large thickness ratio the sound lap joint of GS-HS could be obtained by LSW regardless of the irradiation of laser beam from thick metal to sheet or otherwise,and the morphology shows it is better when the laser is irradiated on the thick metal.Nevertheless,when the laser beam was applied on thick metal of HPS,blind hole or blowhole was formed in the center of joint,which is attributed to the shrinkage during solidification of the molten pool.Small pores or dispersed porosity appeared on the faying face of the joint without predetermined gap which provides the degassing.However,the increase of predetermined gap could reduce the shear strength and nugget size.Two kinds of joints made by LSW have superior shear strength than those made by RSW when the laser were applied on galvanized sheet.
基金Project(51805416) supported by the National Natural Science Foundation of ChinaProject(2019QNRC001) supported by the Young Elite Scientists Sponsorship Program by CAST,China+1 种基金Project(2021JJ20059) supported by the Hunan Provincial Natural Science Foundation for Excellent Young Scholars,ChinaProject(2019RS1002) supported by the Huxiang High-Level Talent Gathering Project of Hunan Province,China。
文摘As one of the advanced and efficient means of joining,the clinching process is capable of joining sheets with different materials or different sheet thicknesses.In this article,a novel modified clinching process,i.e.,the dieless clinching process,was executed to join AA6061 aluminum alloy with sheet thicknesses of 1.5,2.0,2.5 and 3.0 mm according to different sheet stack-ups.The geometrical characteristics,microhardness distribution,failure behavior,static strength,absorbed energy and instantaneous stiffness of the novel dieless joint were gotten and investigated.The results indicated that the sheet thickness ratio has a notable effect on the failure behavior and mechanical properties of the novel dieless clinched joint,and a relatively large sheet thickness ratio can improve the joint performance when joining sheets with different sheet thicknesses.
文摘BACKGROUND The hemoglobin-to-red cell distribution width ratio(HRR)is a recently intro-duced,easily accessible marker that provides insights into inflammation and the tumor vascular microenvironment.It has been suggested to have prognostic value for overall survival in various types of cancer,including urothelial carcinoma,lung cancer,and hepatocellular carcinoma.It has not yet been sufficiently invest-igated in colorectal cancers(CRC).AIM To investigate the prognostic significance of the HRR and other inflammation-based hematological markers in patients with metastatic CRC.Additionally,the study evaluated the impact of surgical interventions,particularly metastasectomy,and multiple clinical and laboratory parameters on overall survival.By iden-tifying low-cost,accessible prognostic indicators,this research seeks to support clinicians in optimizing treatment strategies and risk stratification for patients with CRC.METHODS In this retrospective study,patients diagnosed with CRC between January 2020 and December 2024 were analyzed.The impact of HRR in conjunction with inflammatory markers and a total of 22 different clinical and laboratory para-meters on overall survival were evaluated using univariate Cox regression and a multivariate model.Survival curves were visualized using Kaplan-Meier analysis.RESULTS A total of 155 patients with CRC were included in the study.The median age was 60 years,and 61.9%presented with de novo metastasis.In the receiver operating characteristic curve and area under the curve analysis performed to determine the optimal cutoff,the values were found to be 6.10 for carcinoembryonic antigen(CEA)(P=0.036),18.85 for platelet-to-red cell distribution width ratio(P=0.028),and 10.87 for platelet distribution width-to-lymphocyte ratio(P=0.028).For neutrophil-to-lymphocyte ratio,systemic immune-inflammation index(SII),platelet-to-lymphocyte ratio(PLR),monocyte-to-lymphocyte ratio,HRR,and carbohydrate antigen 19-9,an optimal cutoff could not be determined using the receiver operating characteristic-area under the curve analysis.Therefore,the median values were adopted as the cutoffs(3.09,835.96,177.50,0.380,0.824,and 21.6,respectively).Univariate analysis identified male gender(P=0.045),being under 65 years of age(P=0.001),history of metastas-ectomy(P=0.001),low serum CEA level(P=0.010),low PLR(P=0.024),low SII(P=0.010),and high HRR(P=0.025)as favorable prognostic factors for overall survival.In the multivariate model,being under 65 years of age[hazard ratio(HR)=1.59,95%confidence interval(CI):1.06-2.39,P=0.025],metastasectomy(HR=0.49,95%CI:0.29-0.85,P=0.011),CEA(HR=1.51,95%CI:1.0-2.28,P=0.048),and PLR(HR=1.63,95%CI:1.09-2.44,P=0.018)emerged as independent prognostic factors for overall survival,whereas gender,SII,and HRR did not retain statistical significance.CONCLUSION In conclusion,low HRR alone was a prognostic indicator.However,when modelled with other inflammatory and clinical parameters,it did not provide a sufficiently strong marker feature.
基金Supported by Tianjin Natural Science Foundation(No.23JCZXJC00140).
文摘AIM:To assess and compare the utility of neutrophil-to-lymphocyte ratio(NLR),platelet-to-lymphocyte ratio(PLR),systemic inflammation index(SII),and red blood cell distribution width(RDW)as potential biomarkers to predict the severity of diabetic retinopathy(DR)in the United States population.METHODS:The observational study enlisted patients diagnosed with DR from the National Health and Nutrition Examination Survey(NHANES)database,spanning the period from 2005 to 2008.The severity of DR was defined according to Early Treatment for Diabetic Retinopathy Study(ETDRs).The effect of NLR,PLR,SII,and RDW on proliferative diabetic retinopathy(PDR)were explored using multivariable logistic regression analysis model.Subgroup analysis and restricted cubic splines(RCS)were conducted to assess the robustness of the correlations across subgroups and to explore nonlinear relationships between four indices and PDR.The receiver operating characteristic(ROC)analysis was employed for the purpose of assessing and evaluating the predictive efficacy of NLR,PLR,SII,and RDW in determining the severity of DR.RESULTS:After adjusting for other confounders(age,gender,race,body mass index,diabetes duration,and HbA1c)in multivariable analysis,a unit increase of PLR×0.1,SII×0.01,and RDW would raise the risk for PDR by 15.6%,22.2%,and 33%,respectively.Particularly,there was a 2.208-fold greater risk of PDR in individuals with an elevated NLR(OR=2.208,95%CI,1.348-3.617,P<0.001).RCS analyses showed positive relationships of four indices and PDR after segmented regression based on their own turning points.The results of ROC analysis revealed that PLR+RDW[area under the curve(AUC)=0.772,95%CI:0.669-0.874]had the best predictive value for PDR,compared with NLR+PLR+SII(AUC=0.697,95%CI:0.570-0.825)or RDW alone(AUC=0.736,95%CI:0.646-0.826).CONCLUSION:The combination of RDW and NLR demonstrates a promising ability to predict the severity of DR across the United States population,and it could be promisingly used in clinics for monitoring the progress of DR.
基金jointly supported by the National Natural Science Foundation of China (42204061)Special Fund for Basic Research Operations of the Institute of Geophysics,China Earthquake Administration (0419501)+1 种基金the Gansu Jishishan6.2 magnitude earthquake scientific investigation (DQJB23Y45) programthe Sichuan Provincial Natural Science Foundation (2023NSFSC0768,2023NSFSC0770)。
文摘Reliable thickness of sedimentary layers is essential for seismic hazard assessment in active fault zones, especially in regions prone to strong earthquakes. This study analyzed the seismic ambient noise data recorded by 60 short-period seismic stations deployed at the Jishishan earthquake source and adjacent areas. The base-order resonance frequencies of sedimentary layers beneath the stations were determined using the horizontal-to-vertical spectral ratio method on ambient noise with diff erent frequencies. Then, a resonance-thickness formula was applied to estimate the sedimentary layer thickness at each station. Finally, the entire regional sediment thickness was obtained via interpolation. The thickness of the sedimentary layer beneath each station was estimated using the equation of the relationship between resonance frequency and sedimentary layer thickness, and fi nally, the distribution of sedimentary layer thickness in the whole region was obtained by interpolation. Results reveal notable spatial variations in sediment thickness in the source and adjacent areas. The shallow sedimentary layer in the source area is relatively thick at approximately 100 m, whereas that in Liugou Village, which is the most severely damaged area, is approximately 150-180 m. In the western region, specifically along the western edge of the Jishishan Mountain rupture and the Pourouliuhe-Cheunhua Nanshan rupture zone, the shallow sedimentary layer is approximately 30-60 m. A comparison between the distribution of seismic secondary hazards and sedimentary layer thickness highlights a strong correlation between these hazards and the amplifi cation eff ects of seismic waves. In regions with thicker sedimentary layers, ground shaking is signifi cantly amplifi ed, resulting in more serious seismic secondary hazards. In addition, the study confi rmed that secondary hazards, such as landslides and liquefaction, were more prevalent in regions with thicker sedimentary layers. These fi ndings provide an important reference for post-earthquake reconstruction, seismic risk assessment, and the development of regional disaster prevention and mitigation strategies..
基金support for this study was jointly given by the NSFC(grants 41930217,42072260 and 42372253)the Youth Innovation Team of Shaanxi Universities.
文摘Determining the evolutionary history of the Permian-Triassic Kunlun-Qaidam Continental Arc is essential to understanding the subduction and closure processes of the South Kunlun Ocean.In this paper,we utilize(La/Yb)N ratios collected from a fi ltered geochemical dataset on Permian to Triassic calc-alkaline rocks(55 wt%–68 wt%SiO_(2))and plutonic rocks within the Kunlun-Qaidam Continental Arc to reconstruct the spatiotemporal variation of the relative crustal thickness.Combined with known geologic observations,we discuss the subduction-accretionary tectonics of the South Kunlun Ocean and the topographic evolution of the Kunlun-Qaidam Continental Arc.Two episodes of crustal thickening and thinning were revealed.The reconstructed thickness reveals two crustal thickening and thinning events for the Kunlun-Qaidam Continental Arc from ca.270 to 210 Ma.The southern sector of the Kunlun-Qaidam Continental Arc is about 7 km thicker than the northern portion,with a maximum thickness of about 55 km at ca.270 and 230 Ma.The ca.270 and 230 Ma crustal thickening events coincide with renewed northward subduction of the South Kunlun Ocean plate and ocean closure,respectively,whereas the ca.270‒240 Ma and ca.230‒210 Ma crustal thinning events may refl ect slab break-off of the oceanic plate and lithospheric collapse during the post-collision extension,respectively.
基金supported by the National Natural Science Foundation of China (No. 41774066)Central Public-interest Scientific Institution Basal Research special(No. DQJB16A0305)
文摘The Xing’an Mongolian Orogenic Belt(XMOB) and the northern margin of North China Craton(NCC) have undergone multistage tectonic superimposition and the tectonic evolution is extremely complicated. We collect the teleseismic data of 44 temporary broadband seismic stations deployed in the XMOB and the northern margin of NCC to calculate the P wave receiver functions. The crustal thickness and average crustal ratio as well as the Poisson’s ratios beneath 33 stations are estimated using the H-κ stacking method. The results show:(1) the crustal thickness of the study area ranges from 38.7 to 42.7 km, with an average thickness of 41.2 km. There is a great difference in crustal thickness on both sides of Solonker suture zone. The characteristics of crustal thickness support the geodynamic model that the Paleo-Asian Ocean subducted and closed at the Solonker suture zone.(2) The Poisson’s ratios in the study area are low, ranging from 0.215 to 0.277, with an average value of 0.243, suggesting that the rock composition of the area is dominated by felsic-acid rocks.(3) There exists a negative correlation between the Poisson’s ratio and the crustal thickness. Combined with the lower values of Poisson’s ratio, we speculate that the delamination is the major mechanism in crustal extension and thinning in the study area.
基金supported by National Natural Science Foundation of China (Nos. 11502301, 11602304 and 62175260)
文摘In order to optimize the laser ablation performance of a micro-thruster with 1U dimensions,which employs a micro semiconductor laser,the impacts of pulse width and glycidyl azide polymer(GAP)thickness on thrust performance were researched.The results showed that with a GAP thickness of 200μm,the single-pulse impulse(I)increased gradually with the increase in the laser pulse width from 50 to 800μs,while the specific impulse(I_(sp)),impulse coupling coefficient(Cm)and ablation efficiency(η)all reached optimal values with a 200μs pulse width.It is worth noting that the optimal pulse width is identical to the ignition delay time.Both Cmandηpeaked with a pulse width of 200μs,reaching 242.22μN W^(-1)and 35.4%,respectively.With the increase in GAP thickness,I and Cmincreased gradually.GAP of different thicknesses corresponded to different optimal laser pulse widths.Under a certain laser pulse width,the optimal GAP thickness should be the most vertical thickness of the ablation pit,and the various propulsion performance parameters at this time were also optimal.With the current laser parameters,the optimal GAP thickness was approximately 150μm,I_(sp)was approximately 322.22 s,andηwas approximately 34.94%.
基金supported by National Natural Science Foundation of China(No.11405025).
文摘The yield ratios of neutron-proton(R(n/p))and^(3)H-^(3)He(R(^(3)H∕^(3)He))with reduced rapidity from 0 to 0.5 were simulated at 50 MeV/u even-even ^(36−56)Ca+^(40)Ca,even-even ^(48−78)Ni+^(58)Ni,and ^(100−139)Sn(every third isotopes)+112 Sn for full reduced impact parameters using the isospin-dependent quantum molecular dynamics(IQMD)model.The neutron and proton density distributions and root-mean-square radii of the reaction systems were obtained using the Skyrme-Hartree-Fock model,which was used for the phase space initialization of the projectile and target in IQMD.We defined the unified neutron skin thickness asΔRnp=<r^(2)>^(1∕2) n−<r^(2)>^(1∕2)p,which was negative for neutron-deficient nuclei.The unifiedΔRnp values for nuclei with the same relative neutron excess from different isotopic chains were nearly equal,except for extreme neutron-rich isotopes,which is a type of scaling behavior.The yield ratios of the three isotopic chain-induced reactions,which depended on the reduced impact parameter and unified neutron skin thickness,were studied.The results showed that both R(n/p)and R(^(3)H∕^(3)He)decreased with a reduced impact parameter for extreme neutron-deficient isotopes;however,they increased with reduced impact parameters for extreme neutron-rich isotopes,and increased with theΔRnp of the projectiles for all reduced impact parameters.In addition,a scaling phenomenon was observed betweenΔR np and the yield ratios in peripheral colli-sions from different isotopic chain projectiles(except for extreme neutron-rich isotopes).Thus,R(n/p)and R(^(3)H∕^(3)He)from peripheral collisions were suggested as experimental probes for extracting the neutron or proton skin thicknesses of non-extreme neutron-rich nuclei from different isotopic chains.
基金Funded by the National Key Research and Development Plan of China (No.2017YFB0310400)the National Natural Science Foundation of China (No.5167020705)
文摘Silicon carbide ceramics with different thicknesses/diameter ratios were prepared by using ultra-fine silicon carbide powder with the sintering additives of 1.0 wt% boron and 1.5 wt% carbon. The influence of thickness/diameter ratio on the microstructure and density of SiC ceramics was investigated in detail. The experimental results show that the addition of boron and carbon sintering aids can promote the densification process of SiC ceramic, leading to the low sintering temperature and improve mechanical properties. At 1950 ℃, SiC ceramic with a density of 99% exhibits Young's modulus, hardness, and flexural strength of 476 MPa, 28.3 GPa, and 334 MPa, respectively. It is found that long holding time has a positive effect on the uniformity of the microstructure and density distribution of SiC ceramics with large thickness/diameter ratios. Additionally, the sintering additive of boron can solid-solve into SiC, and then facilitate the phase transformation of SiC to form 6H-SiC and 4H-SiC composite ceramics.
基金financially supported by the National Key R&D Program of China (Grant No.2022YFB2603000)the National Natural Science Foundation of China (Grant Nos.51779172 and 52179076)。
文摘Three-dimensional direct numerical simulations of the wake flow downstream of a near-wall circular cylinder at different gap ratios and boundary layer thicknesses are carried out by using the iterative immersed boundary method.The non-dimensional gap between the cylinder and the wall,G/D=0.2,0.6 and 1.0,the non-dimensional boundary layer thickness,δ/D=0.0,0.7 and 1.6,the Reynolds number,Re=350,and the aspect ratio of the cylinder,L/D=25are adopted.High-resolution visualizations of the complex vortex structures at differentδ/D and G/D are presented.The transition of the streamwise vortex mode,the combined effects ofδ/D and G/D on the flow statistics,the pressure and shear stress distribution and the hydrodynamic forces are analyzed.Results show that with decreasing G/D and increasingδ/D,the gap flow and its vortex-shedding are significantly weakened,together with an elongated wake and an enlarged low-velocity area near the wall,leading to the wake mode transition from the two-sided to one-sided vortex-shedding.Different relative positions of the cylinder regarding the boundary layer alter the flow features of the shear layers.With an increase inδ/D,the front stagnation point shifts to the upper surface,and the distance between the flow divergence point and the maximum pressure position increases.The mean drag coefficient and r.m.s.values of drag and lift coefficients decrease with a decrease in G/D and an increase inδ/D,while the mean lift coefficient increases with decreasing G/D but decreases with increasingδ/D.
文摘The present analysis demonstrates the thermal effect on vibrations of a symmetric, non-homoge- neous trapezoidal plate with parabolically varying thickness in both directions. The variation in Young’s modulus and mass density is the main cause for the occurrence of non-homogeneity in plate’s material. In this consideration, density varies linearly in one direction. The governing differential equations have been derived by Rayleigh-Ritz method in order to attain fundamental frequencies. With C-S-C-S boundary condition, a two term deflection function has been considered. The effect of structural parameters such as taper constants, thermal gradient, aspect ratio and non-homogeneity constant has been investigated for first two modes of vibration. The obtained numerical results have been presented in tabular and graphical form.
