A series of true triaxial unloading tests are conducted on sandstone specimens with a single structural plane to investigate their mechanical behaviors and failure characteristics under different in situ stress states...A series of true triaxial unloading tests are conducted on sandstone specimens with a single structural plane to investigate their mechanical behaviors and failure characteristics under different in situ stress states.The experimental results indicate that the dip angle of structural plane(θ)and the intermediate principal stress(σ2)have an important influence on the peak strength,cracking mode,and rockburst severity.The peak strength exhibits a first increase and then decrease as a function ofσ2 for a constantθ.However,whenσ2 is constant,the maximum peak strength is obtained atθof 90°,and the minimum peak strength is obtained atθof 30°or 45°.For the case of an inclined structural plane,the crack type at the tips of structural plane transforms from a mix of wing and anti-wing cracks to wing cracks with an increase inσ2,while the crack type around the tips of structural plane is always anti-wing cracks for the vertical structural plane,accompanied by a series of tensile cracks besides.The specimens with structural plane do not undergo slabbing failure regardless ofθ,and always exhibit composite tensile-shear failure whatever theσ2 value is.With an increase inσ2 andθ,the intensity of the rockburst is consistent with the tendency of the peak strength.By analyzing the relationship between the cohesion(c),internal friction angle(φ),andθin sandstone specimens,we incorporateθinto the true triaxial unloading strength criterion,and propose a modified linear Mogi-Coulomb criterion.Moreover,the crack propagation mechanism at the tips of structural plane,and closure degree of the structural plane under true triaxial unloading conditions are also discussed and summarized.This study provides theoretical guidance for stability assessment of surrounding rocks containing geological structures in deep complex stress environments.展开更多
AIM:To describe the alterations of the vitreous pathology and anterior chamber(AC)angle structures following transscleral cyclophotocoagulation(TSCP)and better understand the mechanism of post-laser intraocular pressu...AIM:To describe the alterations of the vitreous pathology and anterior chamber(AC)angle structures following transscleral cyclophotocoagulation(TSCP)and better understand the mechanism of post-laser intraocular pressure(IOP)reduction in angle-closure glaucoma(ACG).METHODS:Porcine eyes ex vivo and rabbit eyes in vivo were used.In porcine eyes,permeability rates of the anterior vitreous cortex(AVC)and anterior hyaloid membrane(AHM)were assessed using Schirmer’s strips.Permeability rates in the circumlental space were compared with or without TSCP bursts.Fluorescein diffusion times from the vitreous to the AC were compared between eyes with and without TSCP.In rabbit eyes,changes in IOP and AC angle structures under ultrasound biomicroscopy(UBM)were evaluated at intervals of 30min,7d,and 14d after TSCP.Vitreous pathology was examined using scanning electron microscopy(SEM)immediately and 14d after TSCP.RESULTS:In porcine eyes(n=20),the median(range)permeability rates were 10.3(range 9.8–10.8)mm/min for the AVC and 4.3(range 3.9–4.9)mm/min for the AHM(P=0.009).Permeability rates in the circumlental space were 4.2(range 3.8–4.9)mm/min in areas without TSCP,6.2(range 5.7–6.8)mm/min in areas with non-burst TSCP,and 11.3(range 10.9–11.8)mm/min in areas with burst TSCP(P=0.002).The median(range)fluorescein diffusion time was 5(range 3–8)min in eyes undergoing TSCP,whereas it was 40min(range 35–68)in eyes without TSCP(P<0.001).In rabbit eyes(n=20),SEM showed immediate localized damage to the AHM,AVC,and posterior lens zonules in areas subjected to TSCP bursts,and obvious lens zonule loss with cellular infiltration and possible vitreous liquefaction by post-op day 14.Persistent widening of AC angles was noted at postoperative days 7 and 14,although a significant reduction in IOP was only observed at postoperative day 7.CONCLUSION:TSCP-induced damage on the zonules,AHM,and AVC potentially enhances fluid outflow from the vitreous,leading to a widened AC angle and vitreous liquefaction in rabbits.These observations offer insights into mechanisms of TSCP in lowering IOP and pathogenic roles of vitreous in ACG.展开更多
The structure of the concave-convex plates has proven to be crucial in optimizing the internal flow characteristics of the electrolyzer for hydrogen production.This paper investigates the impact of the gradual expansi...The structure of the concave-convex plates has proven to be crucial in optimizing the internal flow characteristics of the electrolyzer for hydrogen production.This paper investigates the impact of the gradual expansion angle of the inlet channel on the internal flow field of alkaline electrolyzers.The flow distribution characteristics of concave-convex plates with different inlet angle structures in the electrolytic cell is discussed.Besides,the system with internal heat source is studied.The results indicate that a moderate gradual expansion angle is beneficial for enhancing fluid uniformity.However,an excessively large gradual expansion angle may lead to adverse reflux phenomena,reducing the overall performance of the electrolytic cell.展开更多
This paper presents an efficient image feature representation method, namely angle structure descriptor(ASD), which is built based on the angle structures of images. According to the diversity in directions, angle str...This paper presents an efficient image feature representation method, namely angle structure descriptor(ASD), which is built based on the angle structures of images. According to the diversity in directions, angle structures are defined in local blocks. Combining color information in HSV color space, we use angle structures to detect images. The internal correlations between neighboring pixels in angle structures are explored to form a feature vector. With angle structures as bridges, ASD extracts image features by integrating multiple information as a whole, such as color, texture, shape and spatial layout information. In addition, the proposed algorithm is efficient for image retrieval without any clustering implementation or model training. Experimental results demonstrate that ASD outperforms the other related algorithms.展开更多
In this paper, an asymmetric array structure of space laser communication receiver is proposed. This structure can greatly reduce alignment requirement, and lighten the signal strength jitter caused by atmospheric tur...In this paper, an asymmetric array structure of space laser communication receiver is proposed. This structure can greatly reduce alignment requirement, and lighten the signal strength jitter caused by atmospheric turbulence. A prototype of the proposed structure is fabricated and a 2.5 Mbit/s on-off keying(OOK) modulated demonstration link over 40 m free space is built. This asymmetric array structure can effectively collect optical signal while rotating in a window angle of ±17°, and the bit error ratio(BER) keeps zero.展开更多
Using the double-difference relocation algo- rithm, we relocated the 20 April 2013 Lushan, Sichuan, earthquake （Ms 7.0）, and its 4,567 aftershocks recorded during the period between 20 April and May 3, 2013. Our res...Using the double-difference relocation algo- rithm, we relocated the 20 April 2013 Lushan, Sichuan, earthquake （Ms 7.0）, and its 4,567 aftershocks recorded during the period between 20 April and May 3, 2013. Our results showed that most aftershocks are relocated between 10 and 20 km depths, but some large aftershocks were relocated around 30 krn depth and small events extended upward near the surface. Vertical cross sections illustrate a shovel-shaped fault plane with a variable dip angle from the southwest to northeast along the fault. Furthermore, the dip angle of the fault plane is smaller around the mainshock than that in the surrounding areas along the fault. These results suggest that it may be easy to generate the strong earthquake in the place having a small dip angle of the fault, which is somewhat similar to the genesis of the 2008 Wenchuan earthquake. The Lushan mainshock is underlain by the seismically anomalous layers with low-Vp, low-Vs, and high-Poisson＇s ratio anomalies, possibly suggesting that the fluid-filled fractured rock matrices might signifi- cantly reduce the effective normal stress on the fault plane to bring the brittle failure. The seismic gap between Lushan and Wenchuan aftershocks is suspected to be vulnerable to future seismic risks at greater depths, if any.展开更多
The reattached boundary layer in the interaction of an oblique shock wave with a flatplate turbulent boundary layer at Mach number 2.25 is studied by means of Direct Numerical Simulation(DNS).The numerical results are...The reattached boundary layer in the interaction of an oblique shock wave with a flatplate turbulent boundary layer at Mach number 2.25 is studied by means of Direct Numerical Simulation(DNS).The numerical results are carefully compared with available experimental and DNS data in terms of turbulence statistics,wall pressure and skin friction.The coherent vortex structures are significantly enhanced due to the shock interaction,and the reattached boundary layer is characterized by large-scale structures in the outer region.The space-time correlation of fluctuating wall shear stress and streamwise velocity fluctuation reveals that the structural inclination angle exhibits a gradual decrease during the recovery process.The scale interactions are analyzed by using a twopoint amplitude modulation correlation.A possible mechanism is proposed to account for the strong amplitude modulation in the downstream region.Moreover,the mean skin-friction is decomposed to understand the physically informed contributions.Unlike the upstream Turbulent Boundary Layer(TBL),the contribution associated with the Turbulence Kinetic Energy(TKE)production is greatly amplified,while the spatial growth contribution induced by the pressure gradient largely inhibits skin-friction generation.Based on bidimensional empirical mode decomposition,the turbulence kinetic energy production contribution is further split into different terms with specific spanwise length scales.展开更多
This paper deals with the concurrent multi-scale optimization design of frame structure composed of glass or carbon fiber reinforced polymer laminates. In the composite frame structure, the fiber winding angle at the ...This paper deals with the concurrent multi-scale optimization design of frame structure composed of glass or carbon fiber reinforced polymer laminates. In the composite frame structure, the fiber winding angle at the micro-material scale and the geometrical parameter of components of the frame in the macro-structural scale are introduced as the independent variables on the two geometrical scales. Considering manufacturing requirements, discrete fiber winding angles are specified for the micro design variable. The improved Heaviside penalization discrete material optimization interpolation scheme has been applied to achieve the discrete optimization design of the fiber winding angle. An optimization model based on the minimum structural compliance and the specified fiber material volume constraint has been established. The sensitivity information about the two geometrical scales design variables are also deduced considering the characteristics of discrete fiber winding angles. The optimization results of the fiber winding angle or the macro structural topology on the two single geometrical scales, together with the concurrent two-scale optimization, is separately studied and compared in the paper. Numerical examples in the paper show that the concurrent multi-scale optimization can further explore the coupling effect between the macro-structure and micro-material of the composite to achieve an ultralight design of the composite frame structure. The novel two geometrical scales optimization model provides a new opportunity for the design of composite structure in aerospace and other industries.展开更多
The crystal structure of 3-（4-methoxyphenyl）-2-（4-methylbenzoyl）-6,7-dihydro-5H-furo[3,2-g]chromene was obtained by X-ray single-crystal diffraction. The molecule is in the triclinic crystal system, space group P1...The crystal structure of 3-（4-methoxyphenyl）-2-（4-methylbenzoyl）-6,7-dihydro-5H-furo[3,2-g]chromene was obtained by X-ray single-crystal diffraction. The molecule is in the triclinic crystal system, space group P1 with a = 11.0745（4）, b = 13.0953（7）, c = 15.8773（8） ？, α = 92.811（4）, β = 104.815（4）, γ = 111.797（4）o, Z = 4, the final R = 0.0567 and w R = 0.1540. X-ray crystal structure data revealed that one asymmetric structure unit of the title compound contained two molecules. The existence of methyl group changed the dihedral angle between furan ring and the phenyl ring at the C2 position of the furo[3,2-g]chromene scaffold as well as the conformation, and had a further influence on the bioactivity of the furo[3,2-g]chromene derivatives.展开更多
基金supports from the National Natural Science Foundation of China (Grant Nos.52004143 and 52374095)the open fund for the Laboratory of Mining Response and Disaster Prevention and Control in Deep Coal Mines (Grant No.SKLMRDPC21KF06).
文摘A series of true triaxial unloading tests are conducted on sandstone specimens with a single structural plane to investigate their mechanical behaviors and failure characteristics under different in situ stress states.The experimental results indicate that the dip angle of structural plane(θ)and the intermediate principal stress(σ2)have an important influence on the peak strength,cracking mode,and rockburst severity.The peak strength exhibits a first increase and then decrease as a function ofσ2 for a constantθ.However,whenσ2 is constant,the maximum peak strength is obtained atθof 90°,and the minimum peak strength is obtained atθof 30°or 45°.For the case of an inclined structural plane,the crack type at the tips of structural plane transforms from a mix of wing and anti-wing cracks to wing cracks with an increase inσ2,while the crack type around the tips of structural plane is always anti-wing cracks for the vertical structural plane,accompanied by a series of tensile cracks besides.The specimens with structural plane do not undergo slabbing failure regardless ofθ,and always exhibit composite tensile-shear failure whatever theσ2 value is.With an increase inσ2 andθ,the intensity of the rockburst is consistent with the tendency of the peak strength.By analyzing the relationship between the cohesion(c),internal friction angle(φ),andθin sandstone specimens,we incorporateθinto the true triaxial unloading strength criterion,and propose a modified linear Mogi-Coulomb criterion.Moreover,the crack propagation mechanism at the tips of structural plane,and closure degree of the structural plane under true triaxial unloading conditions are also discussed and summarized.This study provides theoretical guidance for stability assessment of surrounding rocks containing geological structures in deep complex stress environments.
基金Supported by National Natural Science Foundation of China(No.82201171,No.82171050,No.82471072).
文摘AIM:To describe the alterations of the vitreous pathology and anterior chamber(AC)angle structures following transscleral cyclophotocoagulation(TSCP)and better understand the mechanism of post-laser intraocular pressure(IOP)reduction in angle-closure glaucoma(ACG).METHODS:Porcine eyes ex vivo and rabbit eyes in vivo were used.In porcine eyes,permeability rates of the anterior vitreous cortex(AVC)and anterior hyaloid membrane(AHM)were assessed using Schirmer’s strips.Permeability rates in the circumlental space were compared with or without TSCP bursts.Fluorescein diffusion times from the vitreous to the AC were compared between eyes with and without TSCP.In rabbit eyes,changes in IOP and AC angle structures under ultrasound biomicroscopy(UBM)were evaluated at intervals of 30min,7d,and 14d after TSCP.Vitreous pathology was examined using scanning electron microscopy(SEM)immediately and 14d after TSCP.RESULTS:In porcine eyes(n=20),the median(range)permeability rates were 10.3(range 9.8–10.8)mm/min for the AVC and 4.3(range 3.9–4.9)mm/min for the AHM(P=0.009).Permeability rates in the circumlental space were 4.2(range 3.8–4.9)mm/min in areas without TSCP,6.2(range 5.7–6.8)mm/min in areas with non-burst TSCP,and 11.3(range 10.9–11.8)mm/min in areas with burst TSCP(P=0.002).The median(range)fluorescein diffusion time was 5(range 3–8)min in eyes undergoing TSCP,whereas it was 40min(range 35–68)in eyes without TSCP(P<0.001).In rabbit eyes(n=20),SEM showed immediate localized damage to the AHM,AVC,and posterior lens zonules in areas subjected to TSCP bursts,and obvious lens zonule loss with cellular infiltration and possible vitreous liquefaction by post-op day 14.Persistent widening of AC angles was noted at postoperative days 7 and 14,although a significant reduction in IOP was only observed at postoperative day 7.CONCLUSION:TSCP-induced damage on the zonules,AHM,and AVC potentially enhances fluid outflow from the vitreous,leading to a widened AC angle and vitreous liquefaction in rabbits.These observations offer insights into mechanisms of TSCP in lowering IOP and pathogenic roles of vitreous in ACG.
基金supported by Science and Technology Projects of Gansu,China(No.22ZD6GA014).
文摘The structure of the concave-convex plates has proven to be crucial in optimizing the internal flow characteristics of the electrolyzer for hydrogen production.This paper investigates the impact of the gradual expansion angle of the inlet channel on the internal flow field of alkaline electrolyzers.The flow distribution characteristics of concave-convex plates with different inlet angle structures in the electrolytic cell is discussed.Besides,the system with internal heat source is studied.The results indicate that a moderate gradual expansion angle is beneficial for enhancing fluid uniformity.However,an excessively large gradual expansion angle may lead to adverse reflux phenomena,reducing the overall performance of the electrolytic cell.
基金supported by the National Natural Science Foundation of China (No.61170145, 61373081, 61402268, 61401260, 61572298)the Technology and Development Project of Shandong (No.2013GGX10125)+1 种基金the Natural Science Foundation of Shandong China (No.BS2014DX006, ZR2014FM012)the Taishan Scholar Project of Shandong, China
文摘This paper presents an efficient image feature representation method, namely angle structure descriptor(ASD), which is built based on the angle structures of images. According to the diversity in directions, angle structures are defined in local blocks. Combining color information in HSV color space, we use angle structures to detect images. The internal correlations between neighboring pixels in angle structures are explored to form a feature vector. With angle structures as bridges, ASD extracts image features by integrating multiple information as a whole, such as color, texture, shape and spatial layout information. In addition, the proposed algorithm is efficient for image retrieval without any clustering implementation or model training. Experimental results demonstrate that ASD outperforms the other related algorithms.
基金supported by the National Natural Science Foundation of China (Nos.61674142 and 62041502)。
文摘In this paper, an asymmetric array structure of space laser communication receiver is proposed. This structure can greatly reduce alignment requirement, and lighten the signal strength jitter caused by atmospheric turbulence. A prototype of the proposed structure is fabricated and a 2.5 Mbit/s on-off keying(OOK) modulated demonstration link over 40 m free space is built. This asymmetric array structure can effectively collect optical signal while rotating in a window angle of ±17°, and the bit error ratio(BER) keeps zero.
基金supported by the National Natural Scientific Foundation of China (41274059 and 40974021)Beijing Natural Scientific Foundation (8122039 and 8092028) to J. LeiSpecial Project for Basic Scientific Research (ZDJ2013-12) to G. Zhang
文摘Using the double-difference relocation algo- rithm, we relocated the 20 April 2013 Lushan, Sichuan, earthquake （Ms 7.0）, and its 4,567 aftershocks recorded during the period between 20 April and May 3, 2013. Our results showed that most aftershocks are relocated between 10 and 20 km depths, but some large aftershocks were relocated around 30 krn depth and small events extended upward near the surface. Vertical cross sections illustrate a shovel-shaped fault plane with a variable dip angle from the southwest to northeast along the fault. Furthermore, the dip angle of the fault plane is smaller around the mainshock than that in the surrounding areas along the fault. These results suggest that it may be easy to generate the strong earthquake in the place having a small dip angle of the fault, which is somewhat similar to the genesis of the 2008 Wenchuan earthquake. The Lushan mainshock is underlain by the seismically anomalous layers with low-Vp, low-Vs, and high-Poisson＇s ratio anomalies, possibly suggesting that the fluid-filled fractured rock matrices might signifi- cantly reduce the effective normal stress on the fault plane to bring the brittle failure. The seismic gap between Lushan and Wenchuan aftershocks is suspected to be vulnerable to future seismic risks at greater depths, if any.
基金co-supported by the National Key R&D Program of China (No. 2019YFA0405300)the National Natural Science Foundation of China (Nos. 11972356 and 91852203)
文摘The reattached boundary layer in the interaction of an oblique shock wave with a flatplate turbulent boundary layer at Mach number 2.25 is studied by means of Direct Numerical Simulation(DNS).The numerical results are carefully compared with available experimental and DNS data in terms of turbulence statistics,wall pressure and skin friction.The coherent vortex structures are significantly enhanced due to the shock interaction,and the reattached boundary layer is characterized by large-scale structures in the outer region.The space-time correlation of fluctuating wall shear stress and streamwise velocity fluctuation reveals that the structural inclination angle exhibits a gradual decrease during the recovery process.The scale interactions are analyzed by using a twopoint amplitude modulation correlation.A possible mechanism is proposed to account for the strong amplitude modulation in the downstream region.Moreover,the mean skin-friction is decomposed to understand the physically informed contributions.Unlike the upstream Turbulent Boundary Layer(TBL),the contribution associated with the Turbulence Kinetic Energy(TKE)production is greatly amplified,while the spatial growth contribution induced by the pressure gradient largely inhibits skin-friction generation.Based on bidimensional empirical mode decomposition,the turbulence kinetic energy production contribution is further split into different terms with specific spanwise length scales.
基金financial support for this research was provided by the Program (Grants 11372060, 91216201) of the National Natural Science Foundation of ChinaProgram (LJQ2015026 ) for Excellent Talents at Colleges and Universities in Liaoning Province+3 种基金the Major National Science and Technology Project (2011ZX02403-002)111 project (B14013)Fundamental Research Funds for the Central Universities (DUT14LK30)the China Scholarship Fund
文摘This paper deals with the concurrent multi-scale optimization design of frame structure composed of glass or carbon fiber reinforced polymer laminates. In the composite frame structure, the fiber winding angle at the micro-material scale and the geometrical parameter of components of the frame in the macro-structural scale are introduced as the independent variables on the two geometrical scales. Considering manufacturing requirements, discrete fiber winding angles are specified for the micro design variable. The improved Heaviside penalization discrete material optimization interpolation scheme has been applied to achieve the discrete optimization design of the fiber winding angle. An optimization model based on the minimum structural compliance and the specified fiber material volume constraint has been established. The sensitivity information about the two geometrical scales design variables are also deduced considering the characteristics of discrete fiber winding angles. The optimization results of the fiber winding angle or the macro structural topology on the two single geometrical scales, together with the concurrent two-scale optimization, is separately studied and compared in the paper. Numerical examples in the paper show that the concurrent multi-scale optimization can further explore the coupling effect between the macro-structure and micro-material of the composite to achieve an ultralight design of the composite frame structure. The novel two geometrical scales optimization model provides a new opportunity for the design of composite structure in aerospace and other industries.
基金supported by the National Natural Science Foundation of China(No.J1103606)the Program for Innovative Research Team of the Ministry of Education of China(No.IRT_14R36)
文摘The crystal structure of 3-（4-methoxyphenyl）-2-（4-methylbenzoyl）-6,7-dihydro-5H-furo[3,2-g]chromene was obtained by X-ray single-crystal diffraction. The molecule is in the triclinic crystal system, space group P1 with a = 11.0745（4）, b = 13.0953（7）, c = 15.8773（8） ？, α = 92.811（4）, β = 104.815（4）, γ = 111.797（4）o, Z = 4, the final R = 0.0567 and w R = 0.1540. X-ray crystal structure data revealed that one asymmetric structure unit of the title compound contained two molecules. The existence of methyl group changed the dihedral angle between furan ring and the phenyl ring at the C2 position of the furo[3,2-g]chromene scaffold as well as the conformation, and had a further influence on the bioactivity of the furo[3,2-g]chromene derivatives.
