First-break picking is the key step in seismic data processing for surveying undulate surfaces, and directly infl uences the precision of near-surface modeling and effects of static corrections. The current first-brea...First-break picking is the key step in seismic data processing for surveying undulate surfaces, and directly infl uences the precision of near-surface modeling and effects of static corrections. The current first-break auto-picking methods may fail when the signalto-noise ratio（SNR） is low for seismic data in the undulate area, and require labor and time intensive manual picking. This study develops an improved super-virtual interferometry（SVI） method that combines multichannel and multidomain quality control（MMQC） techniques to achieve auto-picked first breaks. The improved SVI method extends the SVI application to enhance the SNR for near-surface scattered waves for the first time, which allows for the SVI method to adapt to first breaks with complex raypaths by linear combination of refractions and near-surface scattered waves. Methods of inverse and multidomain interferometry are developed to effectively enhance the virtual records extracted by the SVI method. The deconvolution filter for waveforms is used to increase resolution and reduce false picks, while the MMQC technique is designed to auto-correct false picks and increase the stability of auto-picking first breaks. The robust technique developed in this study enables stable processing of large 3D seismic datasets. Higher quality results are obtained using the approach presented in this paper to actual field data from the mountain areas in western China, when compared to some commonly used commercial software.展开更多
Low molecular weight peptide (LMWP) was prepared from clam Paphia undulate and its antiaging effect on D-galactose-induced acute aging in rats, aged Kunming mice, ultraviolet-exposed rats, and thermally injured rats w...Low molecular weight peptide (LMWP) was prepared from clam Paphia undulate and its antiaging effect on D-galactose-induced acute aging in rats, aged Kunming mice, ultraviolet-exposed rats, and thermally injured rats was investigated. P. undulate flesh was homogenized and digested using papain under optimal conditions, then subjected to Sephadex G-25 chromatography to isolate the LMWP. Administration of LMWP significantly reversed D-galactose-induced oxidative stress by increasing the activities of glutathione peroxidase (GPx) and catalase (CAT), and by decreasing the level of malondialdehyde (MDA). This process was accompanied by increased collagen synthesis. The LMWP prevented photoaging and promoted dermis recovery and remission of elastic fiber hyperplasia. Furthermore, treatment with the LMWP helped to regenerate elastic fibers and the collagen network, increased superoxide dismutase (SOD) in the serum and significantly decreased MDA. Thermal scald-induced inflammation and edema were also relieved by the LWMP, while wound healing in skin was promoted. These results suggest that the LMWP from P. undulate could serve as a new antiaging substance in cosmetics.展开更多
In the present study, scapaundulin C(1), a new labdane diterpenoid, and four related known compounds scapaundulin A(2), 5?, 8?, 9?-trihydroxy-13E-labden-12-one(3), 5?, 8?-dihydroxy-13E-labden-12-one(4), and(13S)-15-hy...In the present study, scapaundulin C(1), a new labdane diterpenoid, and four related known compounds scapaundulin A(2), 5?, 8?, 9?-trihydroxy-13E-labden-12-one(3), 5?, 8?-dihydroxy-13E-labden-12-one(4), and(13S)-15-hydroxylabd-8(17)-en-19-oic acid(5), were isolated from the Chinese liverwort Scapania undulate(L.) Dum., using column chromatography. The structures of these compounds were determined on the basis of 1D- and 2D-NMR analyses. The acetylcholinesterase(Ach E) inhibitory activity was evaluated using a bioautographic TLC assay and the cytotoxic activity was evaluated by the MTT method. All the compounds were reported for the first time to exhibit moderate Ach E inhibitory activity with minimal inhibitory quantities ranging from 250 to 500 ng. All the compounds were tested for their cytotoxicity against five human tumor cell lines, A549, K562, A2780, Hela, and HT29, and compounds 3 and 4 exhibited moderate inhibitory effects on the growth of A2780 cells.展开更多
Magnetic field gradient tensor technique provides abundant data for delicate inversion of subsurface magnetic susceptibility distribution. Large scale magnetic data inversion imaging requires high speed and accuracy f...Magnetic field gradient tensor technique provides abundant data for delicate inversion of subsurface magnetic susceptibility distribution. Large scale magnetic data inversion imaging requires high speed and accuracy for forward modeling. For arbitrarily distributed susceptibility data on an undulated surface, we propose a fast 3D forward modeling method in the wavenumber domain based on(1) the wavenumber-domain expression of the prism combination model and the Gauss–FFT algorithm and(2) cubic spline interpolation. We apply the proposed 3D forward modeling method to synthetic data and use weighting coefficients in the wavenumber domain to improve the modeling for multiple observation surfaces, and also demonstrate the accuracy and efficiency of the proposed method.展开更多
Two-dimensional(2D)porphyrin(Por)-based covalent organic frameworks(COFs)provide an attractive and effective strategy for photocatalytic CO_(2)reduction,but the layered structure due toπ–πstacking is challenging fo...Two-dimensional(2D)porphyrin(Por)-based covalent organic frameworks(COFs)provide an attractive and effective strategy for photocatalytic CO_(2)reduction,but the layered structure due toπ–πstacking is challenging for the exposure of active sites and transfer of mass and photogenerated carriers.In this study,a series of 2D conjugated porphyrin-based COFs were prepared using porphyrin blocks with linking units having different degrees of twisting.According to the experimental and theoretical calculation results,owing to the large spatial steric hindrance between the two carbazole units connected by the N–N single bond,a greatly undulating layered structure was formed in NN-Por-COF,which enhanced mass transfer and exposed more catalytic sites.The introduction of carbazole also modulated the electronic structure of the porphyrin Co center,which lowered the reaction energy barrier.The optimization of the structural and electronic effects led to the excellent photocatalytic CO_(2)reduction performance of NN-Por-COF,with CO conversion rates as high as 22.38 and 3.02 mmol g−1 h−1 under pure and diluted(10%)CO_(2)atmosphere,respectively,which are superior to those of most of the reported porphyrin-based photocatalysts.展开更多
This study evaluates the physical mechanisms of incident waves as they interact with a porous wavy barrier of finite thickness.A wave-trapping chamber is formed between the thick wavy barrier(TWB)and partially reflect...This study evaluates the physical mechanisms of incident waves as they interact with a porous wavy barrier of finite thickness.A wave-trapping chamber is formed between the thick wavy barrier(TWB)and partially reflecting seawall(PRS).The effect of seabed undulations is incorporated into the wave-trapping analysis of the TWB.The boundary value problem proposed in this study is solved using a multidomain boundary element method within the context of linear potential flow theory.Coefficients such as reflection,runup,horizontal force on PRS,and vertical force on TWB are examined for various structural configurations.The position of seabed undulations is analyzed for four scenarios:i)seabed undulations upwave of the wavy barrier with a trapping chamber,ii)seabed undulations upwave of the wavy barrier without a trapping chamber,iii)seabed undulations underneath the wavy barrier with a trapping chamber,and iv)seabed undulations beneath the wavy barrier without a trapping chamber.The study results are compared with known results to verify their accuracy.The effects of PRS,TWB porosity,trapping chamber,plate thickness,seabed type,and submergence depth on hydrodynamic coefficients are analyzed against relative water depth.The study reveals that the introduction of a porous TWB with a trapping chamber results in minimal hydrodynamic coefficients(reduced reflection and force on a wall)compared to a rigid TWB without a trapping chamber.A comparison of various seabeds is reported for all combinations of TWB with a chamber.The sloping seabed upwave of the barrier with a trapping chamber,20%plate porosity,and 50%wall reflection at an appropriate submergence depth could replace gravity-type breakwaters in deeper waters.This study holds great potential for analyzing wave trapping coefficients by TWB to provide an effective coastal protection system.展开更多
Coal wall stability is a critical factor influencing coal mining efficiency and threatens the safety of working faces,where irregular coal wall surfaces significantly affect the contact and support effectiveness of th...Coal wall stability is a critical factor influencing coal mining efficiency and threatens the safety of working faces,where irregular coal wall surfaces significantly affect the contact and support effectiveness of the support plate,thereby impacting stability.Through a combination of theoretical analysis,mechanical testing,and numerical simulations,this study establishes a mechanical model of irregular coal wall surfaces to investigate the effects of the undulation period and undulation height on coal wall failure characteristics.This research reveals the mechanical response mechanisms of irregular coal wall surfaces and proposes an innovative method to enhance coal wall stability by improving the supporting cushion material of the support plate,which was validated through numerical simulations.The results show that the undulation height and undulation period significantly influence the macroscopic mechanical parameters of the samples,with the undulation height exerting a more pronounced effect.The strength of the samples with undulating surfaces is approximately 50%-60% that of the samples with flat surfaces.The failure mode under uniaxial compression is predominantly tensile,resulting in long and slender block fragments with a characteristic“Ⅲ”-shaped tensile fracture pattern.During the loading process,samples with undu-lating surfaces dissipate energy at all stages,with a greater proportion of energy dissipation occurring during the early loading stage because of structural damage and the formation of internal cracks.The surface compressive and tensile stresses are correlated with the curvature radius of the convex surface and the elastic modulus of the supporting plate.Reducing the elastic modulus of the supporting plate material can effectively alleviate the stress concentration at convex locations and increase the peak strength.This study provides theoretical foundations and technical references for the prevention and control of coal wall spalling in deep thick coal seam mining.展开更多
Fractures in rock strata serve as flow pathways for gas flow.The undulation of fracture channels can influence the guidance of gas flow.In this context,four-point bending experiments on prefabricated fractured rocks a...Fractures in rock strata serve as flow pathways for gas flow.The undulation of fracture channels can influence the guidance of gas flow.In this context,four-point bending experiments on prefabricated fractured rocks at different angles under stable stepped loading stress.The experiment results clarified the evolutionary law that the undulation degree of the rock tensile fracture surface is separated by an initial fracture angle of 45°.The high undulation intervals were less than 45°,whereas the low undulation intervals were more than 45°.Furthermore,the relative undulation degree,undulation frequency,and matching degree of the fracture surface were quantified.The relationship between the change in fracture surface undulation and gas flow guidance was established.Based on this,the stability,tortuosity,and uniformity of the gas flow in the fracture channel were quantitatively characterized.Subsequently,numerical models of the fracture channels were constructed to validate the indices proposed in this study.The results of the study clarified the influence of different initial fracture angles on the undulation changes of fracture surfaces,and established the relationship between these changes and gas flow,which is conducive to understanding the role of internal fracture channels in rocks in guiding the gas flow process.展开更多
The objective of this work is to investigate the dynamics of a self-propelled undulating sheet in a non-Newtonian electrolyte solution inside a wavy channel under the electroosmotic effect.The electrolyte solution,whi...The objective of this work is to investigate the dynamics of a self-propelled undulating sheet in a non-Newtonian electrolyte solution inside a wavy channel under the electroosmotic effect.The electrolyte solution,which is non-Newtonian,is modeled as a Carreau-Yasuda fluid.The flow generated by a combination of an undulating sheet and electroosmotic effect is obtained by solving the continuity and momentum equations.The electroosmotic body force term is derived using the Poisson-Boltzmann equation for the electric potential.A fourth-order ordinary differential equation for the stream function is solved under the Stokes flow regime.The dynamics of the undulating sheet’s speed and the energy dissipation it,are investigated.The combined effects of electroosmosis and the viscoelastic properties of the ambient fluid on the undulating sheet are discussed.展开更多
A theoretical study of the influence of a quasi-electrostatic support on the amplification level of the slow space charge wave(SCW) in the amplification section of a superheterodyne free electron laser(FEL) was carrie...A theoretical study of the influence of a quasi-electrostatic support on the amplification level of the slow space charge wave(SCW) in the amplification section of a superheterodyne free electron laser(FEL) was carried out. One of the ways to significantly increase the saturation level of the slow SCW is maintaining the conditions of a three-wave parametric resonance between the slow, fast SCWs and the resulting pump electric field. This can be done by introducing the quasielectrostatic support in the superheterodyne FEL amplification section. Also, it was found that the generated pump electric field significantly influences the maintenance of parametric resonance conditions. As a result, this increases the saturation level of the slow SCW by 70%. Finally, the quasi-electrostatic support significantly reduces the maximum value of the electrostatic undulator pump field strength, which is necessary to achieve the maximum saturation level of the slow SCW.展开更多
A new on-chip light source configuration has been proposed,which utilizes the interaction between a microwave or laser and a dielectric nanopillar array to generate a periodic electromagnetic near-field and applies pe...A new on-chip light source configuration has been proposed,which utilizes the interaction between a microwave or laser and a dielectric nanopillar array to generate a periodic electromagnetic near-field and applies periodic transverse acceleration to relativistic electrons to generate high-energy photon radiation.The dielectric nanopillar array interacting with the driving field acts as an electron undulator,in which the near-field drives electrons to oscillate.When an electron beam propagates through this nanopillar array in this light source configuration,it is subjected to a periodic transverse near-field force and will radiate X-ray or evenγ-ray high-energy photons after a relativistic frequency up-conversion.Compared with the undulator which is based on the interaction between strong lasers and nanostructures to generate a plasmonic near-field,this configuration is less prone to damage during operation.展开更多
Unfavorable fishy odour is an inevitable problem in aquatic products. In the present study, headspace solid-phase mi- croextraction gas chromatography mass spectrometry （HS-SPME-GC-MS） analysis of volatiles from unt...Unfavorable fishy odour is an inevitable problem in aquatic products. In the present study, headspace solid-phase mi- croextraction gas chromatography mass spectrometry （HS-SPME-GC-MS） analysis of volatiles from untreated samples and three deodorized samples （under the optimal conditions） ofPaphia undulata enzymatic hydrolysate revealed that the compounds contrib- uting to the distinctive odor were 1-octen-3-ol, n-hexanal, n-heptanal, 2,4-heptadienal, and 2,4-decadienal, whereas n-pentanal, n-octanal, n-octanol, benzaldehyde, 2-ethylfuran and 2-pentylfuran were the main contributors to the aromatic flavor. The deodoriz- ing effects of activated carbon （AC） adsorption, yeast extract （YE） masking and tea polyphenol （TP） treatment on a P. undulata en- zymatic hydrolysate were investigated using orthogonal experiments with sensory evaluation as the index. The following optimized deodorization conditions were obtained： AC adsorption （35 mg mL-1, 80℃, 40 rain）, YE masking （7 mgmL l, 45 ℃, 30 min） and TP treatment （0.4mgmL-l, 40℃, 50min）. AC adsorption effectively removed off-flavor volatile aldehydes and ketones. YE masking modified the odor profile by increasing the relative contents of aromatic compounds and decreasing the relative contents of aldehydes and ketones. The TP treatment was not effective in reducing the odor score, but it significantly reduced the relative content of alde- hydes while increasing that of alkanes. It is also notable that TP effectively suppressed trimethylamine （TMA） formation in a P. un- dulate hydrolysate solution for a period of 72 h.展开更多
Engineering seismic exploration aims at shallow imaging which is confused by statics if the surface is uneven. Direct pre-stack depth migration （DPDM） is based on accurate elevations of sources and receivers, by whi...Engineering seismic exploration aims at shallow imaging which is confused by statics if the surface is uneven. Direct pre-stack depth migration （DPDM） is based on accurate elevations of sources and receivers, by which static correction is completely abandoned before migration and surely the imaging quality is remarkably improved. To obtain some artificial shot gathers, high-order staggered-grid finite-difference （FD） method is adapted to model acoustic wave propagation. Since the shot gathers are always disturbed by regular interferences, the statics still must be applied to supporting the interference elimination by apparent velocity filtering method. Then all the shot gathers should be removed back to their original positions by reverse statics. Finally, they are migrated by pre-stack reverse-time depth migration and imaged. The numerical experiments show that the DPDM can ideally avoid the mistakes caused by statics and increase imaging precision.展开更多
The distribution and migration of houbara bustard in China was studied by range investigation and tracking through PTT satellite transmitter from 1997 to 2004. The houbara bustard occurs in the Junggar Basin, north pa...The distribution and migration of houbara bustard in China was studied by range investigation and tracking through PTT satellite transmitter from 1997 to 2004. The houbara bustard occurs in the Junggar Basin, north part of Tacheng Basin and valley of Ulungur river in northern Xinjiang, southern part of Turpan Basin and Barkol in eastern Xinjiang. In Inner Mongolia, the houbara bustard occurs in Urathouqi, Alxahouqi and Ejinaqi. In Gansu province, the houbara bustard occurs in Wuwei, Minqin and Shandan. The whole range is not contiguous area. Houbara bastard started migration from Junggar Basin in northern Xinjiang, Turpan Basin and Barkol in eastern Xinjiang, Wuwei in western Gansu Province and Bayan Nur in western Inner Mongolia in the middle of September. Flying to the west and northwest, via Junggar Basin and area between Bole and Habahe in northern Xinjiang, entered Kazakhstan, they turned toward southwest, passed Uzbekistan and Turkmenistan, arrived in Arabia Bay of southern Iran or flied over Afghanistan, arrived in southern Pakistan for wintering. The whole migration usually took 35 +/- 13 days covering a distance of 4 800-7 000 km. In the next year, houbara went back to the breeding grounds in China through the same routes at the beginning of March. However, it took the birds 64 +/- 17 days to finish the spring migration. They arrived in breeding site between middle of April and late May. The sub-adults arrived later and did not breed.展开更多
基金supported by the National Basic Research Program of China(No.2013CB228602)the National Science and Technology Major Project of China(No.2011ZX05004-003)the National High Tech Research Program of China(No.2013AA064202)
文摘First-break picking is the key step in seismic data processing for surveying undulate surfaces, and directly infl uences the precision of near-surface modeling and effects of static corrections. The current first-break auto-picking methods may fail when the signalto-noise ratio（SNR） is low for seismic data in the undulate area, and require labor and time intensive manual picking. This study develops an improved super-virtual interferometry（SVI） method that combines multichannel and multidomain quality control（MMQC） techniques to achieve auto-picked first breaks. The improved SVI method extends the SVI application to enhance the SNR for near-surface scattered waves for the first time, which allows for the SVI method to adapt to first breaks with complex raypaths by linear combination of refractions and near-surface scattered waves. Methods of inverse and multidomain interferometry are developed to effectively enhance the virtual records extracted by the SVI method. The deconvolution filter for waveforms is used to increase resolution and reduce false picks, while the MMQC technique is designed to auto-correct false picks and increase the stability of auto-picking first breaks. The robust technique developed in this study enables stable processing of large 3D seismic datasets. Higher quality results are obtained using the approach presented in this paper to actual field data from the mountain areas in western China, when compared to some commonly used commercial software.
基金Supported by the Knowledge Innovation Program of Chinese Academy of Sciences(No.KZCX2-EW-Q214)the Comprehensive Strategic Cooperation Programs between Guangdong Province and Chinese Academy of Sciences(Nos.2011A090100008,2009B091300018,2010B090300027)the Marine Fisheries Technology Promotion Special Program of Guangdong Province,China(No.A2009009-035(a))
文摘Low molecular weight peptide (LMWP) was prepared from clam Paphia undulate and its antiaging effect on D-galactose-induced acute aging in rats, aged Kunming mice, ultraviolet-exposed rats, and thermally injured rats was investigated. P. undulate flesh was homogenized and digested using papain under optimal conditions, then subjected to Sephadex G-25 chromatography to isolate the LMWP. Administration of LMWP significantly reversed D-galactose-induced oxidative stress by increasing the activities of glutathione peroxidase (GPx) and catalase (CAT), and by decreasing the level of malondialdehyde (MDA). This process was accompanied by increased collagen synthesis. The LMWP prevented photoaging and promoted dermis recovery and remission of elastic fiber hyperplasia. Furthermore, treatment with the LMWP helped to regenerate elastic fibers and the collagen network, increased superoxide dismutase (SOD) in the serum and significantly decreased MDA. Thermal scald-induced inflammation and edema were also relieved by the LWMP, while wound healing in skin was promoted. These results suggest that the LMWP from P. undulate could serve as a new antiaging substance in cosmetics.
基金financially supported by National Natural Science Foundation of China(No.30925038)
文摘In the present study, scapaundulin C(1), a new labdane diterpenoid, and four related known compounds scapaundulin A(2), 5?, 8?, 9?-trihydroxy-13E-labden-12-one(3), 5?, 8?-dihydroxy-13E-labden-12-one(4), and(13S)-15-hydroxylabd-8(17)-en-19-oic acid(5), were isolated from the Chinese liverwort Scapania undulate(L.) Dum., using column chromatography. The structures of these compounds were determined on the basis of 1D- and 2D-NMR analyses. The acetylcholinesterase(Ach E) inhibitory activity was evaluated using a bioautographic TLC assay and the cytotoxic activity was evaluated by the MTT method. All the compounds were reported for the first time to exhibit moderate Ach E inhibitory activity with minimal inhibitory quantities ranging from 250 to 500 ng. All the compounds were tested for their cytotoxicity against five human tumor cell lines, A549, K562, A2780, Hela, and HT29, and compounds 3 and 4 exhibited moderate inhibitory effects on the growth of A2780 cells.
基金supported by the National Special Plan for the 13th Five-Year Plan of China(No.2017YFC0602204-10)Independent Exploration of the Innovation Project for Graduate Students at Central South University(No.2017zzts176)+3 种基金National Natural Science Foundation of China(Nos.41574127,41404106,and 41674075)Postdoctoral Fund Projects of China(No.2017M622608)National Key R&D Program of China(No.2018YFC0603602)Natural Science Youth Fund Project of the Hunan Province,China(No.2018JJ3642)
文摘Magnetic field gradient tensor technique provides abundant data for delicate inversion of subsurface magnetic susceptibility distribution. Large scale magnetic data inversion imaging requires high speed and accuracy for forward modeling. For arbitrarily distributed susceptibility data on an undulated surface, we propose a fast 3D forward modeling method in the wavenumber domain based on(1) the wavenumber-domain expression of the prism combination model and the Gauss–FFT algorithm and(2) cubic spline interpolation. We apply the proposed 3D forward modeling method to synthetic data and use weighting coefficients in the wavenumber domain to improve the modeling for multiple observation surfaces, and also demonstrate the accuracy and efficiency of the proposed method.
基金supported by the National Natural Science Foundation of China(22235001,22175020,and 22271012)the Fundamental Research Funds for the Central Universities(FRF-IDRY-23-021,FRF-BR-23-02B,and FRF-TP-24-014A)+1 种基金University of Science and Technology Beijingsupported by the User Experiment Assist System of Shanghai Synchrotron Radiation Facility.
文摘Two-dimensional(2D)porphyrin(Por)-based covalent organic frameworks(COFs)provide an attractive and effective strategy for photocatalytic CO_(2)reduction,but the layered structure due toπ–πstacking is challenging for the exposure of active sites and transfer of mass and photogenerated carriers.In this study,a series of 2D conjugated porphyrin-based COFs were prepared using porphyrin blocks with linking units having different degrees of twisting.According to the experimental and theoretical calculation results,owing to the large spatial steric hindrance between the two carbazole units connected by the N–N single bond,a greatly undulating layered structure was formed in NN-Por-COF,which enhanced mass transfer and exposed more catalytic sites.The introduction of carbazole also modulated the electronic structure of the porphyrin Co center,which lowered the reaction energy barrier.The optimization of the structural and electronic effects led to the excellent photocatalytic CO_(2)reduction performance of NN-Por-COF,with CO conversion rates as high as 22.38 and 3.02 mmol g−1 h−1 under pure and diluted(10%)CO_(2)atmosphere,respectively,which are superior to those of most of the reported porphyrin-based photocatalysts.
文摘This study evaluates the physical mechanisms of incident waves as they interact with a porous wavy barrier of finite thickness.A wave-trapping chamber is formed between the thick wavy barrier(TWB)and partially reflecting seawall(PRS).The effect of seabed undulations is incorporated into the wave-trapping analysis of the TWB.The boundary value problem proposed in this study is solved using a multidomain boundary element method within the context of linear potential flow theory.Coefficients such as reflection,runup,horizontal force on PRS,and vertical force on TWB are examined for various structural configurations.The position of seabed undulations is analyzed for four scenarios:i)seabed undulations upwave of the wavy barrier with a trapping chamber,ii)seabed undulations upwave of the wavy barrier without a trapping chamber,iii)seabed undulations underneath the wavy barrier with a trapping chamber,and iv)seabed undulations beneath the wavy barrier without a trapping chamber.The study results are compared with known results to verify their accuracy.The effects of PRS,TWB porosity,trapping chamber,plate thickness,seabed type,and submergence depth on hydrodynamic coefficients are analyzed against relative water depth.The study reveals that the introduction of a porous TWB with a trapping chamber results in minimal hydrodynamic coefficients(reduced reflection and force on a wall)compared to a rigid TWB without a trapping chamber.A comparison of various seabeds is reported for all combinations of TWB with a chamber.The sloping seabed upwave of the barrier with a trapping chamber,20%plate porosity,and 50%wall reflection at an appropriate submergence depth could replace gravity-type breakwaters in deeper waters.This study holds great potential for analyzing wave trapping coefficients by TWB to provide an effective coastal protection system.
基金the National Key Research and Development Program of China(Nos.2023YFC2907501 and 2023YFC2907503)the National Natural Science Foundation of China(Nos.52374106 and 52274154)the Fundamental Research Funds for the Central Universities(No.2023YQTD02).
文摘Coal wall stability is a critical factor influencing coal mining efficiency and threatens the safety of working faces,where irregular coal wall surfaces significantly affect the contact and support effectiveness of the support plate,thereby impacting stability.Through a combination of theoretical analysis,mechanical testing,and numerical simulations,this study establishes a mechanical model of irregular coal wall surfaces to investigate the effects of the undulation period and undulation height on coal wall failure characteristics.This research reveals the mechanical response mechanisms of irregular coal wall surfaces and proposes an innovative method to enhance coal wall stability by improving the supporting cushion material of the support plate,which was validated through numerical simulations.The results show that the undulation height and undulation period significantly influence the macroscopic mechanical parameters of the samples,with the undulation height exerting a more pronounced effect.The strength of the samples with undulating surfaces is approximately 50%-60% that of the samples with flat surfaces.The failure mode under uniaxial compression is predominantly tensile,resulting in long and slender block fragments with a characteristic“Ⅲ”-shaped tensile fracture pattern.During the loading process,samples with undu-lating surfaces dissipate energy at all stages,with a greater proportion of energy dissipation occurring during the early loading stage because of structural damage and the formation of internal cracks.The surface compressive and tensile stresses are correlated with the curvature radius of the convex surface and the elastic modulus of the supporting plate.Reducing the elastic modulus of the supporting plate material can effectively alleviate the stress concentration at convex locations and increase the peak strength.This study provides theoretical foundations and technical references for the prevention and control of coal wall spalling in deep thick coal seam mining.
基金supported by the National Natural Science Foundation of China(No.52522405)Henan Provincial Natural Science Foundation(No.252300421323).
文摘Fractures in rock strata serve as flow pathways for gas flow.The undulation of fracture channels can influence the guidance of gas flow.In this context,four-point bending experiments on prefabricated fractured rocks at different angles under stable stepped loading stress.The experiment results clarified the evolutionary law that the undulation degree of the rock tensile fracture surface is separated by an initial fracture angle of 45°.The high undulation intervals were less than 45°,whereas the low undulation intervals were more than 45°.Furthermore,the relative undulation degree,undulation frequency,and matching degree of the fracture surface were quantified.The relationship between the change in fracture surface undulation and gas flow guidance was established.Based on this,the stability,tortuosity,and uniformity of the gas flow in the fracture channel were quantitatively characterized.Subsequently,numerical models of the fracture channels were constructed to validate the indices proposed in this study.The results of the study clarified the influence of different initial fracture angles on the undulation changes of fracture surfaces,and established the relationship between these changes and gas flow,which is conducive to understanding the role of internal fracture channels in rocks in guiding the gas flow process.
文摘The objective of this work is to investigate the dynamics of a self-propelled undulating sheet in a non-Newtonian electrolyte solution inside a wavy channel under the electroosmotic effect.The electrolyte solution,which is non-Newtonian,is modeled as a Carreau-Yasuda fluid.The flow generated by a combination of an undulating sheet and electroosmotic effect is obtained by solving the continuity and momentum equations.The electroosmotic body force term is derived using the Poisson-Boltzmann equation for the electric potential.A fourth-order ordinary differential equation for the stream function is solved under the Stokes flow regime.The dynamics of the undulating sheet’s speed and the energy dissipation it,are investigated.The combined effects of electroosmosis and the viscoelastic properties of the ambient fluid on the undulating sheet are discussed.
文摘A theoretical study of the influence of a quasi-electrostatic support on the amplification level of the slow space charge wave(SCW) in the amplification section of a superheterodyne free electron laser(FEL) was carried out. One of the ways to significantly increase the saturation level of the slow SCW is maintaining the conditions of a three-wave parametric resonance between the slow, fast SCWs and the resulting pump electric field. This can be done by introducing the quasielectrostatic support in the superheterodyne FEL amplification section. Also, it was found that the generated pump electric field significantly influences the maintenance of parametric resonance conditions. As a result, this increases the saturation level of the slow SCW by 70%. Finally, the quasi-electrostatic support significantly reduces the maximum value of the electrostatic undulator pump field strength, which is necessary to achieve the maximum saturation level of the slow SCW.
基金pported by the National Natural Science Foundation of China(Grant Nos.12325409,12388102,12074398,and U2267204)the CAS Project for Young Scientists in Basic Research(Grant No.YSBR-060)the Shanghai Pilot Program for Basic Research,Chinese Academy of Sciences Shanghai Branch。
文摘A new on-chip light source configuration has been proposed,which utilizes the interaction between a microwave or laser and a dielectric nanopillar array to generate a periodic electromagnetic near-field and applies periodic transverse acceleration to relativistic electrons to generate high-energy photon radiation.The dielectric nanopillar array interacting with the driving field acts as an electron undulator,in which the near-field drives electrons to oscillate.When an electron beam propagates through this nanopillar array in this light source configuration,it is subjected to a periodic transverse near-field force and will radiate X-ray or evenγ-ray high-energy photons after a relativistic frequency up-conversion.Compared with the undulator which is based on the interaction between strong lasers and nanostructures to generate a plasmonic near-field,this configuration is less prone to damage during operation.
基金supported by the Public Science and Technology Research Funds Projects of Ocean (No.201305018)the National Key Technology Research and Development Program for the 12th Five-Year Plan (No.2012BAD33B10)+3 种基金the National Natural Science Foundation of Guangdong, China (Nos. 2014A 030310351 and 2014A030310338)the Innovative Development of Marine Economy Regional Demonstration Projects of Guangdong (Nos.SZHY2012-B01-004 and GD2013-B03-001)the Science and Technology Planning Project of Guangdong Province, China (Nos.2013B 090800002 and 2015B090904003)the National Science Foundation for Young Scientists of China (No.31101271)
文摘Unfavorable fishy odour is an inevitable problem in aquatic products. In the present study, headspace solid-phase mi- croextraction gas chromatography mass spectrometry （HS-SPME-GC-MS） analysis of volatiles from untreated samples and three deodorized samples （under the optimal conditions） ofPaphia undulata enzymatic hydrolysate revealed that the compounds contrib- uting to the distinctive odor were 1-octen-3-ol, n-hexanal, n-heptanal, 2,4-heptadienal, and 2,4-decadienal, whereas n-pentanal, n-octanal, n-octanol, benzaldehyde, 2-ethylfuran and 2-pentylfuran were the main contributors to the aromatic flavor. The deodoriz- ing effects of activated carbon （AC） adsorption, yeast extract （YE） masking and tea polyphenol （TP） treatment on a P. undulata en- zymatic hydrolysate were investigated using orthogonal experiments with sensory evaluation as the index. The following optimized deodorization conditions were obtained： AC adsorption （35 mg mL-1, 80℃, 40 rain）, YE masking （7 mgmL l, 45 ℃, 30 min） and TP treatment （0.4mgmL-l, 40℃, 50min）. AC adsorption effectively removed off-flavor volatile aldehydes and ketones. YE masking modified the odor profile by increasing the relative contents of aromatic compounds and decreasing the relative contents of aldehydes and ketones. The TP treatment was not effective in reducing the odor score, but it significantly reduced the relative content of alde- hydes while increasing that of alkanes. It is also notable that TP effectively suppressed trimethylamine （TMA） formation in a P. un- dulate hydrolysate solution for a period of 72 h.
文摘Engineering seismic exploration aims at shallow imaging which is confused by statics if the surface is uneven. Direct pre-stack depth migration （DPDM） is based on accurate elevations of sources and receivers, by which static correction is completely abandoned before migration and surely the imaging quality is remarkably improved. To obtain some artificial shot gathers, high-order staggered-grid finite-difference （FD） method is adapted to model acoustic wave propagation. Since the shot gathers are always disturbed by regular interferences, the statics still must be applied to supporting the interference elimination by apparent velocity filtering method. Then all the shot gathers should be removed back to their original positions by reverse statics. Finally, they are migrated by pre-stack reverse-time depth migration and imaged. The numerical experiments show that the DPDM can ideally avoid the mistakes caused by statics and increase imaging precision.
基金financed by international cooperation between China and UZE:Project of Houbara Conservation and Ecological Monitoring in China (0866031)The Key Projects of Chinese Academy of Sciences (KZ295-JI-114)
文摘The distribution and migration of houbara bustard in China was studied by range investigation and tracking through PTT satellite transmitter from 1997 to 2004. The houbara bustard occurs in the Junggar Basin, north part of Tacheng Basin and valley of Ulungur river in northern Xinjiang, southern part of Turpan Basin and Barkol in eastern Xinjiang. In Inner Mongolia, the houbara bustard occurs in Urathouqi, Alxahouqi and Ejinaqi. In Gansu province, the houbara bustard occurs in Wuwei, Minqin and Shandan. The whole range is not contiguous area. Houbara bastard started migration from Junggar Basin in northern Xinjiang, Turpan Basin and Barkol in eastern Xinjiang, Wuwei in western Gansu Province and Bayan Nur in western Inner Mongolia in the middle of September. Flying to the west and northwest, via Junggar Basin and area between Bole and Habahe in northern Xinjiang, entered Kazakhstan, they turned toward southwest, passed Uzbekistan and Turkmenistan, arrived in Arabia Bay of southern Iran or flied over Afghanistan, arrived in southern Pakistan for wintering. The whole migration usually took 35 +/- 13 days covering a distance of 4 800-7 000 km. In the next year, houbara went back to the breeding grounds in China through the same routes at the beginning of March. However, it took the birds 64 +/- 17 days to finish the spring migration. They arrived in breeding site between middle of April and late May. The sub-adults arrived later and did not breed.
