A 400 km-long wide-angle seismic experiment along Lianxian-Gangkou profile in South China was carried out to study contact relationship between southeast continental margin of Yangtze block and northwest continental m...A 400 km-long wide-angle seismic experiment along Lianxian-Gangkou profile in South China was carried out to study contact relationship between southeast continental margin of Yangtze block and northwest continental margin of Cathaysia block. We reconstructed crustal wide-angle reflection structure by the depth-domain pre-stack migration and the crustal velocity model constructed from the traveltime fitting. The wide-angle reflection section shows different reflection （from crystalline basement and Moho） pattern beneath the Yangtze and Cathaysia blocks, and suggests the Wuchuan-Sihui fault is the boundary between them. A cluster of well-developed reflections on Moho and in its underlying topmost mantle probably comes from alternative thin layers, which may be seismic signature of strong interaction between crust and mantle in the tectonic environment of lithosphere extension.展开更多
The studies of seismic tomography and wide-angle reflection have been carried out to reveal the velocity structUrebeneath the eastern Dabie orogenic belt. The result from the seismic tomography shows the high velocity...The studies of seismic tomography and wide-angle reflection have been carried out to reveal the velocity structUrebeneath the eastern Dabie orogenic belt. The result from the seismic tomography shows the high velocity bodiesmight be positioned to a depth of only about 1 .5 km below sea level within the Dabie ultra-high pressure metamorphic (UHPM) belt; the fan-profile shows the Shuihou-Wuhe fault, the demarcation between the South Dabieand the North Dabie, slopes to the south-west at a dip angle of about 45° in the bottom of upper crust. The wideangle reflection shows the middle crustal boundaries and the complex features from the lower crust.展开更多
The Fuzhou basin and its vicinities are located at the northern end of the southeastern coastal seismic zone of the mainland of China. By the joint explorations of high-resolution seismic refraction and wide-angle ref...The Fuzhou basin and its vicinities are located at the northern end of the southeastern coastal seismic zone of the mainland of China. By the joint explorations of high-resolution seismic refraction and wide-angle reflection/refraction as well as deep seismic reflection in the region, which is the first synthetic profile in China, its fine velocity structure and geometric structure from the ground to Moho discontinuity is obtained. The result shows that the crust is obviously layered with a thickness of about 32 km. Basically, it consists of two parts: upper crust and lower crust. The velocity of the upper crust is 5.9-6.2 km/s in which there is a 3-4-km-thick weak low-velocity layer between the depths of 10-15 km, while the velocity of the lower crust in the range of 6.3-7.2 km/s. There exists a strong velocity gradient layer about 3 km thick above the Moho discontinuity whose velocity increases from 6.5 to 7.27 km/s. There exist high-angle normal faults that are small in size and extend only in the shallow crust. These faults are the secondary developed on the hanging wall of westward dipping low-angle normal faults. Thus, their seismogenic ability is limited, however, there exists a high-angle deep fault in the crust from Changle-Zaoan fault zone to seashore fault zone. This deep fault has cut the interface between the upper and lower crusts and Moho discontinuity, and may be the deep structure to trigger destructive earthquake source in future to affect Fuzhou City. These results have advanced the detecting precision of the deep structure in the southeastern coastal seismic zone of the mainland of China. In the aspect of the combined feature of the deep and shallow extensional structures that consist of the westward dipping low-angle normal faults and secondary normal faults on their hanging walls in the upper crust, it is firstly obtained that a united structural interpretation has deepened the knowledge about the deep dynamic process in the southeastern coastal seismic zone. At the same time, in synthetic application of deep seismic detecting methods for deep tectonic background, it possesses a wide referenced meaning to the other regions.展开更多
The design and fabrication of graded-refractive-index （GRIN） antireflection （AR） coatings with wide-angle and broadband characteristics are demonstrated. The optimization of the graded-index profiles with a geneti...The design and fabrication of graded-refractive-index （GRIN） antireflection （AR） coatings with wide-angle and broadband characteristics are demonstrated. The optimization of the graded-index profiles with a genetic algorithm is used in the design of the GRIN AR coatings. The average reflectance over a wavelength range from 400 nm to 800 nm and angles of incidence from 0° to 80° could be reduced to only 0.1% by applying an optimized AR coating onto BK7 glass. The optimization of step-graded GRIN AR coating is then further investigated in detail. A two-layer AR coating was deposited by electron beam evaporation with glancing angle deposition technology, and the positional homogeneity was improved by depositing the film from two opposite directions. The microstructure of the AR coating was investigated by scanning electron microscopy, and the residual reflectances of the coating sample are in agreement with theoretical calculations. The optimized GRIN AR coatings are beneficial to increasing the efficiency of light utilization.展开更多
The 3-D crustal structure of P-wave velocity in East China is studied based on the data obtained by wide-angle seismic reflection and refraction surveys.The results suggest that a deep Moho disconti-nuity exists in th...The 3-D crustal structure of P-wave velocity in East China is studied based on the data obtained by wide-angle seismic reflection and refraction surveys.The results suggest that a deep Moho disconti-nuity exists in the western zone of the study region,being 35―48 thick.High-velocity structure zones exist in the upper crust shallower than 20 km beneath the Sulu and Dabie regions.The cause of high-velocity zones is attributable to high-pressure metamorphic(HPM) and ultra-high-pressure metamorphic(UHPM) terranes with high velocity and density exhuming up to the upper crust in the Sulu and Dabie orogenies.Anomalous zones of low velocity are in the lower crust,about 30 km beneath the Sulu and Dabie regions.The Moho discontinuity is as deep as 38 km beneath the Dabie region,deeper than those in the surrounding areas.The Moho discontinuity beneath the Sulu orogenic region is also a little deeper than those in its vicinity,being about 32 km.The deep Moho discontinuity zone implies that the low crustal velocity structure zone is in that region.The low-velocity characteristics in the lower crust are probably related to the remnant crustal root of the old mountains due to the orogeny in the Sulu and Dabie regions.The high-velocity anomalous zones in the upper crust and low-velocity anomalous zones in the lower crust beneath the Sulu region are all located northeast of the northern segment of the Tan-Lu fault.However,the high-and low-velocity anomalous zones beneath the Dabie region are located southwest of the southern segment of the Tan-Lu fault.Such a distribution of the velocity-anomalous zones looks to be attributable a left lateral slip motion along the Tan-Lu fault.The distribution pattern of the velocity-anomalous zones may show some evidence for the left strike-slip motion regime of the Tan-Lu fault.展开更多
Electromagnetic interference(EMI)shielding materials with superior shielding efficiency and low-reflection properties hold promising potential for utilization across electronic components,precision instruments,and fif...Electromagnetic interference(EMI)shielding materials with superior shielding efficiency and low-reflection properties hold promising potential for utilization across electronic components,precision instruments,and fifth-generation communication equipment.In this study,multistage microcellular waterborne polyurethane(WPU)composites were constructed via gradient induction,layer-by-layer casting,and supercritical carbon dioxide foaming.The gradient-structured WPU/ironcobalt loaded reduced graphene oxide(FeCo@rGO)foam serves as an impedance-matched absorption layer,while the highly conductive WPU/silver loaded glass microspheres(Ag@GM)layer is employed as a reflection layer.Thanks to the incorporation of an asymmetric structure,as well as the introduction of gradient and porous configurations,the composite foam demonstrates excellent conductivity,outstanding EMI SE(74.9 dB),and minimal reflection characteristics(35.28%)in 8.2-12.4 GHz,implying that more than 99.99999%of electromagnetic(EM)waves were blocked and only 35.28%were reflected to the external environment.Interestingly,the reflectivity of the composite foam is reduced to 0.41%at 10.88 GHz due to the resonance for incident and reflected EM waves.Beyond that,the composite foam is characterized by low density(0.47 g/cm^(3))and great stability of EMI shielding properties.This work offers a viable approach for craft-ing lightweight,highly shielding,and minimally reflective EMI shielding composites.展开更多
Metasurfaces composed of two-dimensional nanopillar arrays can manipulate light fields in desirable ways and exhibit the unique advantage of beam steering.Here,we experimentally demonstrate a metasurface-based wide-an...Metasurfaces composed of two-dimensional nanopillar arrays can manipulate light fields in desirable ways and exhibit the unique advantage of beam steering.Here,we experimentally demonstrate a metasurface-based wide-angle broadband all-dielectric blazed grating with an extreme incident angle of up to 80°,which is achieved by optimizing the wide-angle phase shifts and transmissivities of the unit cells.It exhibits a maximum diffraction efficiency of 72%and a high average efficiency of 64%over a wide range of incident angles from−80° to 45° at 1.55μm.Moreover,the proposed grating has a broad bandwidth of 200 nm(1.45-1.65μm),and average efficiencies of more than 50%can be achieved experimentally over the same incidence angles.Our results may pave the way for the creation of novel and efficient flat optical devices for wavefront control.展开更多
The emergent metagrating,with its unique and flexible beam shaping capabilities,offers new paths to efficient modulation of acoustic waves.In this work,an acoustic metagrating is demonstrated for high-efficiency and w...The emergent metagrating,with its unique and flexible beam shaping capabilities,offers new paths to efficient modulation of acoustic waves.In this work,an acoustic metagrating is demonstrated for high-efficiency and wide-angle anomalous refraction.It is shown that the normal reflection and transmission can be totally suppressed by properly modulating the amplitude and phase characteristics of the metagrating supercells for high-efficiency anomalous refraction.The anomalous refraction behavior is achieved in the wide range of incident angles from 28°to 78°,and the efficiency of-1st order diffraction is higher than 90%by finely designing the metagrating structure.The anomalous refraction behaviors are verified experimentally at incidence angle of 28°,45°,and 78°,respectively.The demonstrated metagrating is anticipated to possess efficient wide-angle composite wavefront engineering applications in such fields as communications.展开更多
Global challenges like epidemics,wars,and climate change expose humans to life-and-death threats daily,triggering death anxiety and subsequent death reflection,which involves deliberate cognitive processing of mortali...Global challenges like epidemics,wars,and climate change expose humans to life-and-death threats daily,triggering death anxiety and subsequent death reflection,which involves deliberate cognitive processing of mortality.While some studies have shown the positive impacts of death reflection,such as on well-being,the relationship between death reflection and existential well-being,closely related to life and death,remains unexplored.This study aimed to investigate the effects of death reflection on existential well-being and the mediating role of relational self-esteem.675 university students from Sichuan and Hubei,China,completed the death reflection scale,relational self-esteem scale,and the existential well-being subscale of the spiritual well-being scale.Results indicated that death reflection was positively correlated with both relational self-esteem and existential well-being,and relational self-esteem was positively related to existential well-being.Mediation analysis confirmed that relational self-esteem mediated the relationship between death reflection and existential well-being.This study not only enriches the research content on the positive effects of death reflection theoretically,but also holds significant practical value in guiding individuals who have experienced death or been exposed to death-related information in their psychological reconstruction and recovery.展开更多
We report an interesting and abnormal electromagnetic phenomenon with regard to a terajet(TJ)that is generated in a reflection mode,which is realized by placing a dielectric scatterer onto a metal reflection plate.We ...We report an interesting and abnormal electromagnetic phenomenon with regard to a terajet(TJ)that is generated in a reflection mode,which is realized by placing a dielectric scatterer onto a metal reflection plate.We show that the introduction of an air hollow into metal reflection plate beneath the scatterer does not induce an expected decrease but an abnormal increase of focal length of the TJ by as much as more than three times.This abnormal phenomenon takes place in case that the air hollow is shallow and there exists a critical hollow depth for a given lateral size of air hollow.Larger than the critical depth,the phenomenon no longer occurs.It is explained from viewpoints of both ray optics in terms of role of relative portion of central waves in TJ formation and electromagnetic field theory with regard to hollow-induced phase singularities.展开更多
Perfect anomalous reflections have been demonstrated in optical phase gradient metasurfaces(PGMs),but they suffer from single-frequency(narrow-band)response due to the intrinsic limitation of natural geometric periodi...Perfect anomalous reflections have been demonstrated in optical phase gradient metasurfaces(PGMs),but they suffer from single-frequency(narrow-band)response due to the intrinsic limitation of natural geometric periodicity.Here,we provide both numerical and analytical evidence that a depth gradient metasurface can achieve discrete ultra-broadband perfect anomalous reflection in the microwave range in the absence of geometric periodicity.Remarkably,by adjusting the operating frequency of the incident wave,the same effect can be steadily obtained via a physically equivalent phase periodicity in the PGM.Based on this mechanism,a perfect retroreflector with a broadband response ranging from 1 GHz to 40 GHz is realized.Our work has promising applications in communication,source tracking,and military satellites.展开更多
U_(S)-admitting spaces,which were introduced by Heckmann,enjoy many nice properties similar to those of the extensively studied well-filtered spaces.In this paper,we present a direct construction of the U_(S)-admittin...U_(S)-admitting spaces,which were introduced by Heckmann,enjoy many nice properties similar to those of the extensively studied well-filtered spaces.In this paper,we present a direct construction of the U_(S)-admitting reflections by using U_(S)-admitting determined sets.展开更多
Curriculum ideological and political education is an important direction of higher education reform in the new era,aiming to realize the organic integration of professional knowledge imparting and ideological and poli...Curriculum ideological and political education is an important direction of higher education reform in the new era,aiming to realize the organic integration of professional knowledge imparting and ideological and political education.Taking preliminary landscape design course as an example,this paper expounded in detail the implementation of teaching reform from three aspects:the formulation of teaching objectives,the integration of teaching contents and the innovation of teaching methods.This paper systematically summarized the implementation effect of ideological and political education reform,and reflected on the excavation of ideological and political elements,integration degree,innovation of teaching methods,teachers’ideological and political ability and practical teaching.The exploration on curriculum ideological and political teaching provides useful reference and thinking for similar courses,and promotes the sustainable development of curriculum ideological and political education.展开更多
The power generation performance of a heaving body wave energy converter(HBWEC)can be enhanced through strategic deployment in proximity to natural or artificial coastal structures.In this study,coastal structures are...The power generation performance of a heaving body wave energy converter(HBWEC)can be enhanced through strategic deployment in proximity to natural or artificial coastal structures.In this study,coastal structures are represented by a partial reflection wall,enabling the device to harness additional reflected wave energy.However,the mechanisms by which the reflection coefficient and the clearance between the wall and the device affect energy conversion performance remain inadequately understood.This study experimentally investigates these effects.The findings demonstrate that the clearance impact on HBWEC power performance near partial reflection walls aligns with standing wave variation characteristics,with optimal positioning near the second antinode of the HBWEC's heaving natural period.Enhanced reflection coefficients improve energy conversion efficiency within the wave spectrum around the device's heaving natural period.Additionally,significant water sloshing observed within the clearance may diminish power performance,as verified through computational fluid dynamics(CFD)analysis.This phenomenon results from the multiplicative relationship of leeside clearance with 0.5λ(λis the wavelength).These insights suggest that practical engineering implementation requires balanced consideration of reflection coefficient,clearance,sloshing phenomenon,and heaving restriction system,rather than individual parameter optimization.展开更多
The marginal sea and back-arc basins in the Western Pacific Ocean have become the focus of tectonics due to their unique tectonic location.To understand the deep crustal structure in the back-arc region,we present a 5...The marginal sea and back-arc basins in the Western Pacific Ocean have become the focus of tectonics due to their unique tectonic location.To understand the deep crustal structure in the back-arc region,we present a 545-kmlong active-source ocean bottom seismometer(OBS)wide-angle reflection/refraction profile in the East China Sea.The P wave velocity model shows that the Moho depth rises significantly,from approximately 30 km in the East China Sea shelf to approximately 16 km in the axis of the Okinawa Trough.The lower crustal high-velocity zone(HVZ)in the southern Okinawa Trough,with V_(p) of 6.8-7.3 km/s,is a remarkable manifestation of the mantle material upwelling and accretion to the lower crust.This confirms that the lower crustal high-velocity mantle accretion is developed in the southern Okinawa Trough.During the process of back-arc extension,the crustal structure of the southern Okinawa Trough is completely invaded and penetrated by the upper mantle material in the axis region.In some areas of the southern central graben,the crust may has broken up and entered the initial stage of seafloor spreading.The discontinuous HVZs in the lower crust in the back-arc region also indicate the migration of spreading centers in the back-arc region since the Cenozoic.The asthenosphere material upwelling in the continent-ocean transition zone is constantly driving the lithosphere eastward for episodic extension,and is causing evident tectonic migration in the Western Pacific back-arc region.展开更多
Fracture identification is important for the evaluation of carbonate reservoirs. However, conventional logging equipment has small depth of investigation and cannot detect rock fractures more than three meters away fr...Fracture identification is important for the evaluation of carbonate reservoirs. However, conventional logging equipment has small depth of investigation and cannot detect rock fractures more than three meters away from the borehole. Remote acoustic logging uses phase-controlled array-transmitting and long sound probes that increase the depth of investigation. The interpretation of logging data with respect to fractures is typically guided by practical experience rather than theory and is often ambiguous. We use remote acoustic reflection logging data and high-order finite-difference approximations in the forward modeling and prestack reverse-time migration to image fractures. First, we perform forward modeling of the fracture responses as a function of the fracture-borehole wall distance, aperture, and dip angle. Second, we extract the energy intensity within the imaging area to determine whether the fracture can be identified as the formation velocity is varied. Finally, we evaluate the effect of the fracture-borehole distance, fracture aperture, and dip angle on fracture identification.展开更多
We introduce the Thomsen anisotropic parameters into the approximate linear reflection coefficient equation for P-SV wave in weakly anisotropic HTI media. From this we get a new, more effective, and practical reflecti...We introduce the Thomsen anisotropic parameters into the approximate linear reflection coefficient equation for P-SV wave in weakly anisotropic HTI media. From this we get a new, more effective, and practical reflection coefficient equation. We performed forward modeling to AVO attributes, obtaining excellent results. The combined AVO attribute analysis of PP and PS reflection data can greatly reduce ambiguity, obtain better petrophysical parameters, and improve parameter accuracy.展开更多
Polarity reversals may occur to transmitted P waves if the incidence angle is greater than the critical incidence angle. We analyze the characteristics of reflection and transmission coefficients under the condition o...Polarity reversals may occur to transmitted P waves if the incidence angle is greater than the critical incidence angle. We analyze the characteristics of reflection and transmission coefficients under the condition of wide incidence angle based on Zoeppritz equations. We find that for specific conditions, as the incidence angle increases, the characteristic curve of the transmitted P-wave coefficient enters the third quadrant from the first quadrant through the origin, which produces a transition in the transmitted P wave and the corresponding coefficient experiences polarity reversal. We derive the incidence angle when the transmitted P-wave coefficient is zero and verify that it equals zero by using finite-difference forward modeling for a single-interface model. We replace the water in the model reservoir by gas and see that the reservoir P-wave velocity and density decrease dramatically. By analyzing the synthetic seismogram of the transmitted P wave in the single-interface model, we show that the gas-saturated reservoir is responsible for polarity reversal.展开更多
基金supported by the Chinese Academy of Sciences (KZCX2-YW-132)the National Natural Sciences Foundation of China(40721003, 40830315)
文摘A 400 km-long wide-angle seismic experiment along Lianxian-Gangkou profile in South China was carried out to study contact relationship between southeast continental margin of Yangtze block and northwest continental margin of Cathaysia block. We reconstructed crustal wide-angle reflection structure by the depth-domain pre-stack migration and the crustal velocity model constructed from the traveltime fitting. The wide-angle reflection section shows different reflection （from crystalline basement and Moho） pattern beneath the Yangtze and Cathaysia blocks, and suggests the Wuchuan-Sihui fault is the boundary between them. A cluster of well-developed reflections on Moho and in its underlying topmost mantle probably comes from alternative thin layers, which may be seismic signature of strong interaction between crust and mantle in the tectonic environment of lithosphere extension.
文摘The studies of seismic tomography and wide-angle reflection have been carried out to reveal the velocity structUrebeneath the eastern Dabie orogenic belt. The result from the seismic tomography shows the high velocity bodiesmight be positioned to a depth of only about 1 .5 km below sea level within the Dabie ultra-high pressure metamorphic (UHPM) belt; the fan-profile shows the Shuihou-Wuhe fault, the demarcation between the South Dabieand the North Dabie, slopes to the south-west at a dip angle of about 45° in the bottom of upper crust. The wideangle reflection shows the middle crustal boundaries and the complex features from the lower crust.
文摘The Fuzhou basin and its vicinities are located at the northern end of the southeastern coastal seismic zone of the mainland of China. By the joint explorations of high-resolution seismic refraction and wide-angle reflection/refraction as well as deep seismic reflection in the region, which is the first synthetic profile in China, its fine velocity structure and geometric structure from the ground to Moho discontinuity is obtained. The result shows that the crust is obviously layered with a thickness of about 32 km. Basically, it consists of two parts: upper crust and lower crust. The velocity of the upper crust is 5.9-6.2 km/s in which there is a 3-4-km-thick weak low-velocity layer between the depths of 10-15 km, while the velocity of the lower crust in the range of 6.3-7.2 km/s. There exists a strong velocity gradient layer about 3 km thick above the Moho discontinuity whose velocity increases from 6.5 to 7.27 km/s. There exist high-angle normal faults that are small in size and extend only in the shallow crust. These faults are the secondary developed on the hanging wall of westward dipping low-angle normal faults. Thus, their seismogenic ability is limited, however, there exists a high-angle deep fault in the crust from Changle-Zaoan fault zone to seashore fault zone. This deep fault has cut the interface between the upper and lower crusts and Moho discontinuity, and may be the deep structure to trigger destructive earthquake source in future to affect Fuzhou City. These results have advanced the detecting precision of the deep structure in the southeastern coastal seismic zone of the mainland of China. In the aspect of the combined feature of the deep and shallow extensional structures that consist of the westward dipping low-angle normal faults and secondary normal faults on their hanging walls in the upper crust, it is firstly obtained that a united structural interpretation has deepened the knowledge about the deep dynamic process in the southeastern coastal seismic zone. At the same time, in synthetic application of deep seismic detecting methods for deep tectonic background, it possesses a wide referenced meaning to the other regions.
文摘The design and fabrication of graded-refractive-index （GRIN） antireflection （AR） coatings with wide-angle and broadband characteristics are demonstrated. The optimization of the graded-index profiles with a genetic algorithm is used in the design of the GRIN AR coatings. The average reflectance over a wavelength range from 400 nm to 800 nm and angles of incidence from 0° to 80° could be reduced to only 0.1% by applying an optimized AR coating onto BK7 glass. The optimization of step-graded GRIN AR coating is then further investigated in detail. A two-layer AR coating was deposited by electron beam evaporation with glancing angle deposition technology, and the positional homogeneity was improved by depositing the film from two opposite directions. The microstructure of the AR coating was investigated by scanning electron microscopy, and the residual reflectances of the coating sample are in agreement with theoretical calculations. The optimized GRIN AR coatings are beneficial to increasing the efficiency of light utilization.
基金Supported partly by National Natural Science Foundation of China (Grant No.40674026)National Special Science Foundation of China (Grant No.200811037)
文摘The 3-D crustal structure of P-wave velocity in East China is studied based on the data obtained by wide-angle seismic reflection and refraction surveys.The results suggest that a deep Moho disconti-nuity exists in the western zone of the study region,being 35―48 thick.High-velocity structure zones exist in the upper crust shallower than 20 km beneath the Sulu and Dabie regions.The cause of high-velocity zones is attributable to high-pressure metamorphic(HPM) and ultra-high-pressure metamorphic(UHPM) terranes with high velocity and density exhuming up to the upper crust in the Sulu and Dabie orogenies.Anomalous zones of low velocity are in the lower crust,about 30 km beneath the Sulu and Dabie regions.The Moho discontinuity is as deep as 38 km beneath the Dabie region,deeper than those in the surrounding areas.The Moho discontinuity beneath the Sulu orogenic region is also a little deeper than those in its vicinity,being about 32 km.The deep Moho discontinuity zone implies that the low crustal velocity structure zone is in that region.The low-velocity characteristics in the lower crust are probably related to the remnant crustal root of the old mountains due to the orogeny in the Sulu and Dabie regions.The high-velocity anomalous zones in the upper crust and low-velocity anomalous zones in the lower crust beneath the Sulu region are all located northeast of the northern segment of the Tan-Lu fault.However,the high-and low-velocity anomalous zones beneath the Dabie region are located southwest of the southern segment of the Tan-Lu fault.Such a distribution of the velocity-anomalous zones looks to be attributable a left lateral slip motion along the Tan-Lu fault.The distribution pattern of the velocity-anomalous zones may show some evidence for the left strike-slip motion regime of the Tan-Lu fault.
基金supported by the Natural Science Foundation of Anhui Province(No.2308085QE146 and 2208085ME116)the National Natural Science Foundation of China(No.52173039)+1 种基金the Natural Science Foundation of Jiangsu Province(No.BK20210894)the Anhui Provincial Universities Outstanding Youth Research Project(No.2023AH020018).
文摘Electromagnetic interference(EMI)shielding materials with superior shielding efficiency and low-reflection properties hold promising potential for utilization across electronic components,precision instruments,and fifth-generation communication equipment.In this study,multistage microcellular waterborne polyurethane(WPU)composites were constructed via gradient induction,layer-by-layer casting,and supercritical carbon dioxide foaming.The gradient-structured WPU/ironcobalt loaded reduced graphene oxide(FeCo@rGO)foam serves as an impedance-matched absorption layer,while the highly conductive WPU/silver loaded glass microspheres(Ag@GM)layer is employed as a reflection layer.Thanks to the incorporation of an asymmetric structure,as well as the introduction of gradient and porous configurations,the composite foam demonstrates excellent conductivity,outstanding EMI SE(74.9 dB),and minimal reflection characteristics(35.28%)in 8.2-12.4 GHz,implying that more than 99.99999%of electromagnetic(EM)waves were blocked and only 35.28%were reflected to the external environment.Interestingly,the reflectivity of the composite foam is reduced to 0.41%at 10.88 GHz due to the resonance for incident and reflected EM waves.Beyond that,the composite foam is characterized by low density(0.47 g/cm^(3))and great stability of EMI shielding properties.This work offers a viable approach for craft-ing lightweight,highly shielding,and minimally reflective EMI shielding composites.
基金support by the Advanced Integrated Optoelectronics Facility at Tianjin University
文摘Metasurfaces composed of two-dimensional nanopillar arrays can manipulate light fields in desirable ways and exhibit the unique advantage of beam steering.Here,we experimentally demonstrate a metasurface-based wide-angle broadband all-dielectric blazed grating with an extreme incident angle of up to 80°,which is achieved by optimizing the wide-angle phase shifts and transmissivities of the unit cells.It exhibits a maximum diffraction efficiency of 72%and a high average efficiency of 64%over a wide range of incident angles from−80° to 45° at 1.55μm.Moreover,the proposed grating has a broad bandwidth of 200 nm(1.45-1.65μm),and average efficiencies of more than 50%can be achieved experimentally over the same incidence angles.Our results may pave the way for the creation of novel and efficient flat optical devices for wavefront control.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2023YFB3811400 and 2022YFB3806000)the National Natural Science Foundation of China(Grant No.12074314)+1 种基金the Science and Technology New Star Program of Shaanxi Province,China(Grant No.2023KJXX-148)the Fundamental Research Funds for the Central Universities。
文摘The emergent metagrating,with its unique and flexible beam shaping capabilities,offers new paths to efficient modulation of acoustic waves.In this work,an acoustic metagrating is demonstrated for high-efficiency and wide-angle anomalous refraction.It is shown that the normal reflection and transmission can be totally suppressed by properly modulating the amplitude and phase characteristics of the metagrating supercells for high-efficiency anomalous refraction.The anomalous refraction behavior is achieved in the wide range of incident angles from 28°to 78°,and the efficiency of-1st order diffraction is higher than 90%by finely designing the metagrating structure.The anomalous refraction behaviors are verified experimentally at incidence angle of 28°,45°,and 78°,respectively.The demonstrated metagrating is anticipated to possess efficient wide-angle composite wavefront engineering applications in such fields as communications.
文摘Global challenges like epidemics,wars,and climate change expose humans to life-and-death threats daily,triggering death anxiety and subsequent death reflection,which involves deliberate cognitive processing of mortality.While some studies have shown the positive impacts of death reflection,such as on well-being,the relationship between death reflection and existential well-being,closely related to life and death,remains unexplored.This study aimed to investigate the effects of death reflection on existential well-being and the mediating role of relational self-esteem.675 university students from Sichuan and Hubei,China,completed the death reflection scale,relational self-esteem scale,and the existential well-being subscale of the spiritual well-being scale.Results indicated that death reflection was positively correlated with both relational self-esteem and existential well-being,and relational self-esteem was positively related to existential well-being.Mediation analysis confirmed that relational self-esteem mediated the relationship between death reflection and existential well-being.This study not only enriches the research content on the positive effects of death reflection theoretically,but also holds significant practical value in guiding individuals who have experienced death or been exposed to death-related information in their psychological reconstruction and recovery.
基金Project supported by the National Natural Science Foundation of China(Grant No.61875148)the Key Awards Program of Cultivating Outstanding Innovative Postgraduates in Arts and Sciences of Tianjin University(Grant No.C1-2022002)+3 种基金the Talent Project of Anhui Science and Technology University(Grant No.DQYJ202304)the University-Level Research Project of Tianjin Sino-German University of Applied Sciences(Grant No.zdkt2018-007)China Association for Science and Technology Young Talent Support Project Doctoral Special Programthe National High-level University Scholarship Program for Graduate Students of China Scholarship Council(Grant No.202406250166)。
文摘We report an interesting and abnormal electromagnetic phenomenon with regard to a terajet(TJ)that is generated in a reflection mode,which is realized by placing a dielectric scatterer onto a metal reflection plate.We show that the introduction of an air hollow into metal reflection plate beneath the scatterer does not induce an expected decrease but an abnormal increase of focal length of the TJ by as much as more than three times.This abnormal phenomenon takes place in case that the air hollow is shallow and there exists a critical hollow depth for a given lateral size of air hollow.Larger than the critical depth,the phenomenon no longer occurs.It is explained from viewpoints of both ray optics in terms of role of relative portion of central waves in TJ formation and electromagnetic field theory with regard to hollow-induced phase singularities.
基金supported by the National Natural Science Foundation of China(Grant Nos.12274313,62275184,and 62411540033)Collaborative Innovation Center of Suzhou Nano Science and Technology,Suzhou Basic Research Project(Grant No.SJC2023003)+1 种基金the Gusu Leading Talent Plan for Scientific and Technological Innovation and Entrepreneurship(Grant No.ZXL2024400)the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘Perfect anomalous reflections have been demonstrated in optical phase gradient metasurfaces(PGMs),but they suffer from single-frequency(narrow-band)response due to the intrinsic limitation of natural geometric periodicity.Here,we provide both numerical and analytical evidence that a depth gradient metasurface can achieve discrete ultra-broadband perfect anomalous reflection in the microwave range in the absence of geometric periodicity.Remarkably,by adjusting the operating frequency of the incident wave,the same effect can be steadily obtained via a physically equivalent phase periodicity in the PGM.Based on this mechanism,a perfect retroreflector with a broadband response ranging from 1 GHz to 40 GHz is realized.Our work has promising applications in communication,source tracking,and military satellites.
基金Supported by the National Natural Science Foundation of China(Grant No.12571507)。
文摘U_(S)-admitting spaces,which were introduced by Heckmann,enjoy many nice properties similar to those of the extensively studied well-filtered spaces.In this paper,we present a direct construction of the U_(S)-admitting reflections by using U_(S)-admitting determined sets.
基金Sponsored by Teaching Research Project of Yangtze University(JY2023028).
文摘Curriculum ideological and political education is an important direction of higher education reform in the new era,aiming to realize the organic integration of professional knowledge imparting and ideological and political education.Taking preliminary landscape design course as an example,this paper expounded in detail the implementation of teaching reform from three aspects:the formulation of teaching objectives,the integration of teaching contents and the innovation of teaching methods.This paper systematically summarized the implementation effect of ideological and political education reform,and reflected on the excavation of ideological and political elements,integration degree,innovation of teaching methods,teachers’ideological and political ability and practical teaching.The exploration on curriculum ideological and political teaching provides useful reference and thinking for similar courses,and promotes the sustainable development of curriculum ideological and political education.
基金supported by the National Natural Science Foundation of China(Grant Nos.52201322,52401323,and52222109)the Fundamental Research Funds for the Central Universities(Grant No.2024ZYGXZR042)+1 种基金Guangdong Basic and Applied Basic Research Foundation(Grant Nos.2022B1515020036 and 2023A1515012144)the Project of State Key Laboratory of Subtropical Building and Urban Science(Grant No.2023ZB14)。
文摘The power generation performance of a heaving body wave energy converter(HBWEC)can be enhanced through strategic deployment in proximity to natural or artificial coastal structures.In this study,coastal structures are represented by a partial reflection wall,enabling the device to harness additional reflected wave energy.However,the mechanisms by which the reflection coefficient and the clearance between the wall and the device affect energy conversion performance remain inadequately understood.This study experimentally investigates these effects.The findings demonstrate that the clearance impact on HBWEC power performance near partial reflection walls aligns with standing wave variation characteristics,with optimal positioning near the second antinode of the HBWEC's heaving natural period.Enhanced reflection coefficients improve energy conversion efficiency within the wave spectrum around the device's heaving natural period.Additionally,significant water sloshing observed within the clearance may diminish power performance,as verified through computational fluid dynamics(CFD)analysis.This phenomenon results from the multiplicative relationship of leeside clearance with 0.5λ(λis the wavelength).These insights suggest that practical engineering implementation requires balanced consideration of reflection coefficient,clearance,sloshing phenomenon,and heaving restriction system,rather than individual parameter optimization.
基金supported by the National Key Basic Research Program of China(Grant No.2013CB429701)the National Natural Science Foundation of China(Grant Nos.41606083,91958210,41606050 and 41210005)+1 种基金AoShan Technological Innovation Projects of National Laboratory for Marine Science and Technology(Qingdao)(2015ASKJ03)National Marine Geological Special Project(DD20190236,DD20190365,DD20190377)。
文摘The marginal sea and back-arc basins in the Western Pacific Ocean have become the focus of tectonics due to their unique tectonic location.To understand the deep crustal structure in the back-arc region,we present a 545-kmlong active-source ocean bottom seismometer(OBS)wide-angle reflection/refraction profile in the East China Sea.The P wave velocity model shows that the Moho depth rises significantly,from approximately 30 km in the East China Sea shelf to approximately 16 km in the axis of the Okinawa Trough.The lower crustal high-velocity zone(HVZ)in the southern Okinawa Trough,with V_(p) of 6.8-7.3 km/s,is a remarkable manifestation of the mantle material upwelling and accretion to the lower crust.This confirms that the lower crustal high-velocity mantle accretion is developed in the southern Okinawa Trough.During the process of back-arc extension,the crustal structure of the southern Okinawa Trough is completely invaded and penetrated by the upper mantle material in the axis region.In some areas of the southern central graben,the crust may has broken up and entered the initial stage of seafloor spreading.The discontinuous HVZs in the lower crust in the back-arc region also indicate the migration of spreading centers in the back-arc region since the Cenozoic.The asthenosphere material upwelling in the continent-ocean transition zone is constantly driving the lithosphere eastward for episodic extension,and is causing evident tectonic migration in the Western Pacific back-arc region.
基金supported by National Petroleum Major Project(Grant No.2011ZX05020-008)
文摘Fracture identification is important for the evaluation of carbonate reservoirs. However, conventional logging equipment has small depth of investigation and cannot detect rock fractures more than three meters away from the borehole. Remote acoustic logging uses phase-controlled array-transmitting and long sound probes that increase the depth of investigation. The interpretation of logging data with respect to fractures is typically guided by practical experience rather than theory and is often ambiguous. We use remote acoustic reflection logging data and high-order finite-difference approximations in the forward modeling and prestack reverse-time migration to image fractures. First, we perform forward modeling of the fracture responses as a function of the fracture-borehole wall distance, aperture, and dip angle. Second, we extract the energy intensity within the imaging area to determine whether the fracture can be identified as the formation velocity is varied. Finally, we evaluate the effect of the fracture-borehole distance, fracture aperture, and dip angle on fracture identification.
基金the National "973" Project (No.2007CB209603) the "863" Project (No.2006AA06Z108)
文摘We introduce the Thomsen anisotropic parameters into the approximate linear reflection coefficient equation for P-SV wave in weakly anisotropic HTI media. From this we get a new, more effective, and practical reflection coefficient equation. We performed forward modeling to AVO attributes, obtaining excellent results. The combined AVO attribute analysis of PP and PS reflection data can greatly reduce ambiguity, obtain better petrophysical parameters, and improve parameter accuracy.
基金the National Natural Science Foundation of China(No.41374123)
文摘Polarity reversals may occur to transmitted P waves if the incidence angle is greater than the critical incidence angle. We analyze the characteristics of reflection and transmission coefficients under the condition of wide incidence angle based on Zoeppritz equations. We find that for specific conditions, as the incidence angle increases, the characteristic curve of the transmitted P-wave coefficient enters the third quadrant from the first quadrant through the origin, which produces a transition in the transmitted P wave and the corresponding coefficient experiences polarity reversal. We derive the incidence angle when the transmitted P-wave coefficient is zero and verify that it equals zero by using finite-difference forward modeling for a single-interface model. We replace the water in the model reservoir by gas and see that the reservoir P-wave velocity and density decrease dramatically. By analyzing the synthetic seismogram of the transmitted P wave in the single-interface model, we show that the gas-saturated reservoir is responsible for polarity reversal.
