The Qinling orogen was formed as a result of the collision between the North and South China blocks. The Qinling orogen represents the location at which the southern and northern parts of the Chinese mainland collided...The Qinling orogen was formed as a result of the collision between the North and South China blocks. The Qinling orogen represents the location at which the southern and northern parts of the Chinese mainland collided, and it's also the intersection of the Central China orogen and the north-south tectonic belt. There is evidence of strong deformation in this orogen, and it has had a long and complex geological history. We investigated the structure of the Moho in the southern Qinling orogen using large dynamite shot imaging techniques. By integrating the analysis of the single-shot and the move-out corrections profile, we determined the structure of the Moho beneath the northern Dabashan thrust belt and the southern Qinling orogen, including the mantle suture beneath Fenghuang mountain. The Moho is divided into two parts by the mantle suture zone beneath Fenghuang mountain:(1) from Ziyang to Hanyin, the north-dipping Moho is at about45–55 km depth and the depth increases rapidly; and(2)from Hanyin to Ningshan, the south-dipping Moho is at about 40–45 km depth and shallows slowly. The mantle suture is located beneath Fenghuang mountain, and the Moho overlaps at this location: the shallower Moho is connected to the northern part of China, and the deeper Moho is connected to the southern part. This may indicate that the lithosphere in the Sichuan basin subducts to the Qinling block and that the subduction frontier reaches at least as far as Fenghuang mountain.展开更多
Active-source surface wave exploration is advantageous because it has high imaging accuracy,is not affected by high-speed layers,and has a low cost;thus,it has unique advantages for investigating shallow surface struc...Active-source surface wave exploration is advantageous because it has high imaging accuracy,is not affected by high-speed layers,and has a low cost;thus,it has unique advantages for investigating shallow surface structures.For the development and utilization of urban underground space,two parameters in the shallow surface are important,namely,the shear wave velocity(V_(S))and the predominant period of the site,which determine the elevation and aseismic grade of the building design.The traditional method is mainly to obtain the two above-mentioned parameters through testing and measuring drilling samples.However,this method is extremely expensive and time consuming.Therefore,in this research,we used the multichannel surface wave acquisition method to extract the fundamental dispersion curve of single-shot data by using the phase shift method and obtain the V_(S) characteristics in the uppermost 40 m by inversion.We arrived at the following two conclusions based on the V_(S) profile.First,the study area can be roughly divided into five layers,among which the layers 0−8 m,14−20 m,and 20−30 m are low-velocity layers,corresponding to miscellaneous fill,a water-bearing sand layer,and a sand layer;therefore,the V_(S) is relatively low.In contrast,the layers at 8−14 m and 30−40 m are high-velocity layers that are mainly composed of clay,with a relatively better compactness and relatively high V_(S) values.In addition,a low-speed anomaly appears abruptly in the high-speed area at 20−40 m.This anomaly,when combined with geological data,suggests that it is an ancient river channel.Second,from the V_(S) value,the V_(Se)(equivalent shear wave velocity)was calculated.The construction site soil was categorized as class III,with good conditions for engineering geology.In addition,we calculated the predominant period of the site to be 0.56-0.77 s based on the V_(S).Therefore,in the overall structural design of the foundation engineering,the natural vibration period of the structure should be strictly controlled to avoid the predominant period of the site.展开更多
In this work, the main reasons for the breakage of 500 kV transmission line are studied. Under low temperature condition, the coverage of the ice results in the disconnection between the aluminum tube and the steel an...In this work, the main reasons for the breakage of 500 kV transmission line are studied. Under low temperature condition, the coverage of the ice results in the disconnection between the aluminum tube and the steel anchor of strain clamp. Using macroscopic analysis, structure stress analysis, force analysis and mechanical property test, the fractured strain clamps are investigated. The crimping of the aluminum tube on the polished rod not on the grooves of the steel anchor leads to the damage of the strain clamps, which is defined as improper crimping. When improper crimping emerges, there will be only friction force between the aluminum tube and the steel anchor without shear force, and the tension of the conductor will be mainly supported by the steel strands which should be supported by both the aluminum tube and steel stands. Therefore, the breaking force of the strain clamp will greatly decrease. The failure analysis helps to promote the proper hydraulic crimping process and the safe operation of the transmission line.展开更多
In order to improve the voltage quality of rural power distribution network, the series capacitor in distribution lines is proposed. The principle of series capacitor compensation technology to improve the quality of ...In order to improve the voltage quality of rural power distribution network, the series capacitor in distribution lines is proposed. The principle of series capacitor compensation technology to improve the quality of rural power distribution lines voltage is analyzed. The real rural power distribution network simulation model is established by Power System Power System Analysis Software Package (PSASP). Simulation analysis the effect of series capacitor compensation technology to improve the voltage quality of rural power distribution network, The simulation results show that the series capacitor compensation can effectively improve the voltage quality and reduce network losses and improve the transmission capacity of rural power distribution network.展开更多
Carbonaceous materials have drawn much attention in potassium-ion batteries (PIBs) due to their low price and superior physicochemical properties. However, the application of carbonaceous materials in PIB anodes is hi...Carbonaceous materials have drawn much attention in potassium-ion batteries (PIBs) due to their low price and superior physicochemical properties. However, the application of carbonaceous materials in PIB anodes is hindered by sluggish kinetics and large volume expansion. Herein, N/S co-doped carbon nanocapsule (NSCN) is constructed for superior K+ storage. The NSCN possesses 3D nanocapsule framework with abundant meso/macropores, which guarantees structural robustness and accelerates ions/electrons transportation. The high-level N/S co-doping in carbon matrix not only generates ample defects and active sites for K+ adsorption, but also expands interlayer distance for facile K+ intercalation/deintercalation. As a result, the NSCN electrode delivers a high reversible capacity (408 mAh g^(−1) at 0.05 A g^(−1)), outstanding rate capability (149 mAh g^(−1) at 5 A g^(−1)) and favorable cycle stability (150m Ah g^(−1) at 2 A g^(−1) after 2000 cycles). Ex situ TEM, Raman and XPS measurements demonstrate the excellent stability and reversibility of NSCN electrode during potassiation/depotassiation process. This work provides inspiration for the optimization of energy storage materials by structure and doping engineering.展开更多
There is a long-term dispute at Moho depth across the Bangong-Nujiang suture (BNS). Due to the complicated and changeable seismic geological condition, it is not easy to acquire images of the reflective Moho in centra...There is a long-term dispute at Moho depth across the Bangong-Nujiang suture (BNS). Due to the complicated and changeable seismic geological condition, it is not easy to acquire images of the reflective Moho in central Tibet. In the support of the SinoProbe project, a series of deep seismic reflection profiles were conducted to image Moho structure across the BNS and the Qiangtang terrane. These profiles extend from the northern Lhasa terrane to the Qiangtang terrane crossing the BNS. Both shot gathers and migration data show clear Moho images beneath the BNS. The Moho depth varies from 75.1 km (~24 s TWT) beneath the northmost Lhasa terrane to 68.9 km (~22 s TWT) beneath southmost Qiangtang terrane, and rises smoothly to 62.6 km (~20 s TWT ) at ~28 km north of the BNS beneath the Qiangtang terrane. We speculate that the Moho appears a 6.2 km sharp offset across the BNS and becomes ~12.5 km shallower from the northmost Lhasa terrane to the south Qiangtang terrane at ~28 km north of the BNS. The viewpoint of Moho depth across the BNS based on deep seismic reflection data is inconsistent with the previous 20 km offset.展开更多
To deal with the problem that the initial velocity of the bullet is difficult to increase,the research on the super-high initial velocity propulsion in the barrel weapon with an adaptive pressure-maintaining chamber a...To deal with the problem that the initial velocity of the bullet is difficult to increase,the research on the super-high initial velocity propulsion in the barrel weapon with an adaptive pressure-maintaining chamber are conducted.Considering the law of gun-powder burning and the flow characteristics of gun-powder gas in multi-chamber,the scheme of super-high initial velocity propulsion with an adaptive pressure-maintaining chamber is designed,the ballistic model of the barrel weapon with super-high velocity bullet propulsion is established.The research results show that the technical scheme can greatly increase the initial velocity of the bullet with the peak pressure keeping nearly the same as the tradition barrel weapon.The research results can provide a theoretical foundation to significantly increase the initial velocity in barrel weapons using solid propellants,and have an important reference value to comprehensively increase the power of the barrel weapons.展开更多
Porous geopolymer precursors were firstly prepared by the direct foaming method using bauxite,fly ash(FA),and metakaolin(MK)as raw materials,and porous mullite ceramics were prepared after ammonium ion exchange and th...Porous geopolymer precursors were firstly prepared by the direct foaming method using bauxite,fly ash(FA),and metakaolin(MK)as raw materials,and porous mullite ceramics were prepared after ammonium ion exchange and then high-temperature sintering.The effects of chemical foaming agent concentration,ion-exchange time,and sintering temperature on porous geopolymerderived mullite ceramics were studied,and the optimal preparation parameters were found.Studies have shown that the concentration of blowing agent had great influence on open porosity(q)and porosity and cell size distributions of geopolymer samples,which in turn affected their compressive strength(σ).Duration of the ion exchange had no obvious effect on the sintered samples,and the amount of mullite phase increased with the increase in the sintering temperature.Mullite foams,possessing an open-celled porous structure,closely resembling that of the starting porous geopolymers produced by directly foaming,were obtained by firing at high temperatures.Stable mullite(3Al_(2)O_(3)·2SiO_(2))ceramic foams with total porosity(ε)of 83.52 vol%,high open porosity of 83.23 vol%,and compressive strength of 1.72 MPa were produced after sintering at 1400 for 2 h in℃ air without adding any sintering additives using commercial MK,bauxite,and FA as raw materials.展开更多
The Pancharatnam–Berry geometric phase has attracted great interest due to the elegant phase control strategy via geometric transformation of optical elements.The commonly used geometric phase is associated with circ...The Pancharatnam–Berry geometric phase has attracted great interest due to the elegant phase control strategy via geometric transformation of optical elements.The commonly used geometric phase is associated with circular polarization states.Here,we show that by exploiting the geometric phase associated with the two elliptical eigenpolarization states in a racemic metallic helix array,exotic features including full range phase modulation for linear polarization states,diverse polarization conversion,and full complex amplitude modulation can be obtained with rotation of the helices.As a proof of concept,several devices for implementing polarization conversion,vortex beam generating,and lateral dual focusing are built with a racemic helix array in the microwave regime.The calculated and experimental results validate our proposals,which can stimulate various advanced metadevices.展开更多
The North Himalayan gneiss domes(NHGD),as one of the extensional structures widely distributed across the southern Tibetan Plateau,are an important window for studying post-collisional diastrophism and magmation as we...The North Himalayan gneiss domes(NHGD),as one of the extensional structures widely distributed across the southern Tibetan Plateau,are an important window for studying post-collisional diastrophism and magmation as well as polymetallic mineralization.However,the deep mechanism for the formation of NHGD remains controversial.The magnetotelluric(MT)method was adopted to study the deep structure of the Cuonadong dome in the Northern Himalayas.The characteristics of the dome were explored by using the MT sounding curves and phase tensors.Three-dimensional(3D)MT inversion was performed to determine the electrical resistivity structure beneath the Cuonadong dome.The preferred 3D electrical resistivity model shows that an obvious low-resistivity anomaly develops beneath the Cuonadong dome which is overlaid by a high-resistivity body and surrounded by an apparent subcircular zone of low-resistivity anomalies.The integrated conductivity(longitudinal conductance)from depths of 1-20 km indicates that the average longitudinal conductance at the core of the Cuonadong dome is about 10,000 S.The high-conductivity anomaly at the core is found to be analogous to that of lava,mainly resulting from the crustal partial melting,and the estimated melt content is 11.0-17.3%.The high conductance surrounding the dome reaches 20,000 S on average,which is mainly attributed to saline fluids.MT results in this study support that the Cuonadong dome experienced magmatic diapirism.Taken together with previous geological and geochemical studies,we suggest that under the east-west(E-W)extensional tectonic setting in southern Tibet,deep crustal partial melting constantly accumulated beneath the dome,and therefore the magmatic diapirism resulted in the formation of the Cuonadong dome.In addition,the MT results also indicate that the development of the Cuonadong dome provides abundant mineralizing fluids and the space for migration of metallogenic fluids for(rare-metal)polymetallic mineralization.展开更多
Since the performance of electronic circuits is becoming rather limited in face of intensively increasing of amount of information and related operations,alloptical processing offers a promising strategy for future in...Since the performance of electronic circuits is becoming rather limited in face of intensively increasing of amount of information and related operations,alloptical processing offers a promising strategy for future information system.It would benefit a great deal if the all-optical processing could be implemented within the developed electronic chips of nanoscale structures.In that it is highly desirable to break the diffraction limit of light for achieving effective light manipulations with deep subwavelength structures compatible with the state-of-the-art nanofabrication processes.It is of fundamental importance to get subwavelength optical localization,that is,squeeze light wave into subwavelength space for achieving freely manipulating of light fields.This review summarizes the development in realizing subwavelength optical localization by exciting toroidal mode in photonic metamaterials.The toroidal excitations in plasmonic metamaterials and Mie resonant metamaterials,in 3D structures and planar metamaterials,with single or few layers in spectral regime from microwave to optical frequencies are surveyed.Based on the discussion on the configurations of toroidal excitations,the recent development on toroidalrelated optical scattering control actively manipulates the toroidal excitations,and promising applications are further investigated and highlighted.展开更多
Thermomechanical damage of nodules in dielectric multilayer coatings that are irradiated by nanosecond laser pulses has been interpreted with respect to mechanical properties and electric-field enhancement.However,the...Thermomechanical damage of nodules in dielectric multilayer coatings that are irradiated by nanosecond laser pulses has been interpreted with respect to mechanical properties and electric-field enhancement.However,the effect of electric-field enhancement in nodular damage,especially the influence of electric-field distributions,has never been directly demonstrated through experimental results,which prevents the achievement of a clear understanding of the damage process of nodular defects.Here,a systematic and comparative study was designed to reveal how electric-field distributions affect the damage behavior of nodules.To obtain reliable results,two series of artificial nodules with different geometries and film absorption characteristics were prepared from monodisperse silica microspheres.After establishing simplified geometrical models of the nodules,the electric-field enhancement was simulated using a three-dimensional finite-difference time-domain code.Then,the damage morphologies of the artificial nodules were directly compared with the simulated electric-field intensity profiles.For both series of nodules,the damage morphologies reproduced our simulated electric-field intensity distributions very well.These results indicated that the electric-field distribution was actually a bridge that connected the nodular mechanical properties to the final thermomechanical damage.Understanding of the damage mechanism of nodules was deepened by obtaining data on the influence of electric-field distributions on the damage behavior of nodules.展开更多
The application of three-dimensional(3D)plasmonic nanostructures as metamaterials(MMs),nano-antennas,and other devices faces challenges in producing metallic nanostructures with easily definable orientations,sophistic...The application of three-dimensional(3D)plasmonic nanostructures as metamaterials(MMs),nano-antennas,and other devices faces challenges in producing metallic nanostructures with easily definable orientations,sophisticated shapes,and smooth surfaces that are operational in the optical regime and beyond.Here,we demonstrate that complex 3D nanostructures can be readily achieved with focused-ion-beam irradiation-induced folding and examine the optical characteristics of plasmonic“nanograter”structures that are composed of free-standing Au films.These 3D nanostructures exhibit interesting 3D hybridization in current flows and exhibit unusual and well-scalable Fano resonances at wavelengths ranging from 1.6 to 6.4 mm.Upon the introduction of liquids of various refractive indices to the structures,a strong dependence of the Fano resonance is observed,with spectral sensitivities of 1400 nm and 2040 nm per refractive index unit under figures of merit of 35.0 and 12.5,respectively,for low-order and high-order resonance in the near-infrared region.This work indicates the exciting,increasing relevance of similarly constructed 3D free-standing nanostructures in the research and development of photonics and MMs.展开更多
With the increasing complexity of power system structures and the increasing penetration of renewable energy,the number of possible power system operation modes increases dramatically.It is difficult to make manual po...With the increasing complexity of power system structures and the increasing penetration of renewable energy,the number of possible power system operation modes increases dramatically.It is difficult to make manual power flow adjustments to establish an initial convergent power flow that is suitable for operation mode analysis.At present,problems of low efficiency and long time consumption are encountered in the formulation of operation modes,resulting in a very limited number of generated operation modes.In this paper,we propose an intelligent power flow adjustment and generation model based on a deep network and reinforcement learning.First,a discriminator is trained to judge the power flow convergence,and the output of this discriminator is used to construct a value function.Then,the reinforcement learning method is adopted to learn a strategy for power flow convergence adjustment.Finally,a large number of convergent power flow samples are generated using the learned adjustment strategy.Compared with the traditional flow adjustment method,the proposed method has significant advantages that the learning of the power flow adjustment strategy does not depend on the parameters of the power system model.Therefore,this strategy can be automatically learned without manual intervention,which allows a large number of different operation modes to be efficiently formulated.The verification results of a case study show that the proposed method can independently learn a power flow adjustment strategy and generate various convergent power flows.展开更多
Community Question Answering(CQA) in web forums, as a classic forum for user communication,provides a large number of high-quality useful answers in comparison with traditional question answering.Development of method...Community Question Answering(CQA) in web forums, as a classic forum for user communication,provides a large number of high-quality useful answers in comparison with traditional question answering.Development of methods to get good, honest answers according to user questions is a challenging task in natural language processing. Many answers are not associated with the actual problem or shift the subjects,and this usually occurs in relatively long answers. In this paper, we enhance answer selection in CQA using multidimensional feature combination and similarity order. We make full use of the information in answers to questions to determine the similarity between questions and answers, and use the text-based description of the answer to determine whether it is a reasonable one. Our work includes two subtasks:(a) classifying answers as good, bad, or potentially associated with a question, and(b) answering YES/NO based on a list of all answers to a question. The experimental results show that our approach is significantly more efficient than the baseline model, and its overall ranking is relatively high in comparison with that of other models.展开更多
Heteroatom doping carbon materials exhibit a huge application potential for energy storage devices(ESDs).Herein,interconnected N/P co-doped carbon nanocage(NP-CNC)was synthesized from pyrene molecules by using nano-Mg...Heteroatom doping carbon materials exhibit a huge application potential for energy storage devices(ESDs).Herein,interconnected N/P co-doped carbon nanocage(NP-CNC)was synthesized from pyrene molecules by using nano-MgO as template and melamine-phytic acid supramolecular aggregate as dopant coupled with KOH activation.The as-prepared NP-CNC possesses interconnected nanocages for electron transportation and abundant micropores for ion adsorption.Moreover,co-doped N/P species in NP-CNC provide active sites and additional pseudocapacitance.Consequently,NP-CNC as electrode material for symmetric supercapacitor exhibits a high gravimetric capacitance of 435 F·g^(-1) at 0.05 A·g^(-1),high volumetric capacitance of 274 F·cm^(-3) at 0.032 A·cm^(-3),and long cycle lifespan with 96.1%capacitance retention after 50,000 cycles.Furthermore,NP-CNC as cathode for zinc-ion hybrid supercapacitor delivers satisfactory energy and power densities of 130.6 Wh·kg^(-1)(82.3 Wh·L^(-1))and 14.4 kW·kg^(-1)(9.1 kWL^(-1)).This work paves a promising approach to the preparation of high capacitance NP-CNC for ESDs.展开更多
基金funded by basic research funds of the Chinese Academy of Geological Sciences (J1628)the National Natural Science Foundation of China (Nos.441590863 and 41430213)+1 种基金the Ministry of Land and Resources of China (Nos.201311159Sino Probe-02-01)
文摘The Qinling orogen was formed as a result of the collision between the North and South China blocks. The Qinling orogen represents the location at which the southern and northern parts of the Chinese mainland collided, and it's also the intersection of the Central China orogen and the north-south tectonic belt. There is evidence of strong deformation in this orogen, and it has had a long and complex geological history. We investigated the structure of the Moho in the southern Qinling orogen using large dynamite shot imaging techniques. By integrating the analysis of the single-shot and the move-out corrections profile, we determined the structure of the Moho beneath the northern Dabashan thrust belt and the southern Qinling orogen, including the mantle suture beneath Fenghuang mountain. The Moho is divided into two parts by the mantle suture zone beneath Fenghuang mountain:(1) from Ziyang to Hanyin, the north-dipping Moho is at about45–55 km depth and the depth increases rapidly; and(2)from Hanyin to Ningshan, the south-dipping Moho is at about 40–45 km depth and shallows slowly. The mantle suture is located beneath Fenghuang mountain, and the Moho overlaps at this location: the shallower Moho is connected to the northern part of China, and the deeper Moho is connected to the southern part. This may indicate that the lithosphere in the Sichuan basin subducts to the Qinling block and that the subduction frontier reaches at least as far as Fenghuang mountain.
基金This study was supported by the National Natural Science Foundation of China(grant nos.42074115,41574094)the National Key R&D Program of China(grant no.2017YFC0601301)+1 种基金the Geological Survey Project of the China Geological Survey(grant no.DD20189132)the Key Laboratory of Deep-Earth Dynamics,Ministry of Natural Resources(grant no.J1901-3).
文摘Active-source surface wave exploration is advantageous because it has high imaging accuracy,is not affected by high-speed layers,and has a low cost;thus,it has unique advantages for investigating shallow surface structures.For the development and utilization of urban underground space,two parameters in the shallow surface are important,namely,the shear wave velocity(V_(S))and the predominant period of the site,which determine the elevation and aseismic grade of the building design.The traditional method is mainly to obtain the two above-mentioned parameters through testing and measuring drilling samples.However,this method is extremely expensive and time consuming.Therefore,in this research,we used the multichannel surface wave acquisition method to extract the fundamental dispersion curve of single-shot data by using the phase shift method and obtain the V_(S) characteristics in the uppermost 40 m by inversion.We arrived at the following two conclusions based on the V_(S) profile.First,the study area can be roughly divided into five layers,among which the layers 0−8 m,14−20 m,and 20−30 m are low-velocity layers,corresponding to miscellaneous fill,a water-bearing sand layer,and a sand layer;therefore,the V_(S) is relatively low.In contrast,the layers at 8−14 m and 30−40 m are high-velocity layers that are mainly composed of clay,with a relatively better compactness and relatively high V_(S) values.In addition,a low-speed anomaly appears abruptly in the high-speed area at 20−40 m.This anomaly,when combined with geological data,suggests that it is an ancient river channel.Second,from the V_(S) value,the V_(Se)(equivalent shear wave velocity)was calculated.The construction site soil was categorized as class III,with good conditions for engineering geology.In addition,we calculated the predominant period of the site to be 0.56-0.77 s based on the V_(S).Therefore,in the overall structural design of the foundation engineering,the natural vibration period of the structure should be strictly controlled to avoid the predominant period of the site.
文摘In this work, the main reasons for the breakage of 500 kV transmission line are studied. Under low temperature condition, the coverage of the ice results in the disconnection between the aluminum tube and the steel anchor of strain clamp. Using macroscopic analysis, structure stress analysis, force analysis and mechanical property test, the fractured strain clamps are investigated. The crimping of the aluminum tube on the polished rod not on the grooves of the steel anchor leads to the damage of the strain clamps, which is defined as improper crimping. When improper crimping emerges, there will be only friction force between the aluminum tube and the steel anchor without shear force, and the tension of the conductor will be mainly supported by the steel strands which should be supported by both the aluminum tube and steel stands. Therefore, the breaking force of the strain clamp will greatly decrease. The failure analysis helps to promote the proper hydraulic crimping process and the safe operation of the transmission line.
文摘In order to improve the voltage quality of rural power distribution network, the series capacitor in distribution lines is proposed. The principle of series capacitor compensation technology to improve the quality of rural power distribution lines voltage is analyzed. The real rural power distribution network simulation model is established by Power System Power System Analysis Software Package (PSASP). Simulation analysis the effect of series capacitor compensation technology to improve the voltage quality of rural power distribution network, The simulation results show that the series capacitor compensation can effectively improve the voltage quality and reduce network losses and improve the transmission capacity of rural power distribution network.
基金the financial supports from the National Natural Science Foundation of China(Grant Nos.51872005,U1508201,52072002)。
文摘Carbonaceous materials have drawn much attention in potassium-ion batteries (PIBs) due to their low price and superior physicochemical properties. However, the application of carbonaceous materials in PIB anodes is hindered by sluggish kinetics and large volume expansion. Herein, N/S co-doped carbon nanocapsule (NSCN) is constructed for superior K+ storage. The NSCN possesses 3D nanocapsule framework with abundant meso/macropores, which guarantees structural robustness and accelerates ions/electrons transportation. The high-level N/S co-doping in carbon matrix not only generates ample defects and active sites for K+ adsorption, but also expands interlayer distance for facile K+ intercalation/deintercalation. As a result, the NSCN electrode delivers a high reversible capacity (408 mAh g^(−1) at 0.05 A g^(−1)), outstanding rate capability (149 mAh g^(−1) at 5 A g^(−1)) and favorable cycle stability (150m Ah g^(−1) at 2 A g^(−1) after 2000 cycles). Ex situ TEM, Raman and XPS measurements demonstrate the excellent stability and reversibility of NSCN electrode during potassiation/depotassiation process. This work provides inspiration for the optimization of energy storage materials by structure and doping engineering.
文摘There is a long-term dispute at Moho depth across the Bangong-Nujiang suture (BNS). Due to the complicated and changeable seismic geological condition, it is not easy to acquire images of the reflective Moho in central Tibet. In the support of the SinoProbe project, a series of deep seismic reflection profiles were conducted to image Moho structure across the BNS and the Qiangtang terrane. These profiles extend from the northern Lhasa terrane to the Qiangtang terrane crossing the BNS. Both shot gathers and migration data show clear Moho images beneath the BNS. The Moho depth varies from 75.1 km (~24 s TWT) beneath the northmost Lhasa terrane to 68.9 km (~22 s TWT) beneath southmost Qiangtang terrane, and rises smoothly to 62.6 km (~20 s TWT ) at ~28 km north of the BNS beneath the Qiangtang terrane. We speculate that the Moho appears a 6.2 km sharp offset across the BNS and becomes ~12.5 km shallower from the northmost Lhasa terrane to the south Qiangtang terrane at ~28 km north of the BNS. The viewpoint of Moho depth across the BNS based on deep seismic reflection data is inconsistent with the previous 20 km offset.
基金Supported by the National Natural Science Foundation of China(51676099,51376090)the Natural Science Foundation of Jiangsu Province(BK20180473)。
文摘To deal with the problem that the initial velocity of the bullet is difficult to increase,the research on the super-high initial velocity propulsion in the barrel weapon with an adaptive pressure-maintaining chamber are conducted.Considering the law of gun-powder burning and the flow characteristics of gun-powder gas in multi-chamber,the scheme of super-high initial velocity propulsion with an adaptive pressure-maintaining chamber is designed,the ballistic model of the barrel weapon with super-high velocity bullet propulsion is established.The research results show that the technical scheme can greatly increase the initial velocity of the bullet with the peak pressure keeping nearly the same as the tradition barrel weapon.The research results can provide a theoretical foundation to significantly increase the initial velocity in barrel weapons using solid propellants,and have an important reference value to comprehensively increase the power of the barrel weapons.
基金supported by the National Natural Science Foundation of China (52002090)the Heilongjiang Postdoctoral Science Foundation Funded Project (LBHZ19051)+2 种基金the Fundamental Research Funds for the Central Universities (XK21000210)the Scientific Research Foundation for the Returned Overseas Chinese Scholars of Heilongjiang Province (2019QD0002)the open fund from Key Laboratory of Superlight Materials and Surface Technology,Ministry of Education (XK2100021044).
文摘Porous geopolymer precursors were firstly prepared by the direct foaming method using bauxite,fly ash(FA),and metakaolin(MK)as raw materials,and porous mullite ceramics were prepared after ammonium ion exchange and then high-temperature sintering.The effects of chemical foaming agent concentration,ion-exchange time,and sintering temperature on porous geopolymerderived mullite ceramics were studied,and the optimal preparation parameters were found.Studies have shown that the concentration of blowing agent had great influence on open porosity(q)and porosity and cell size distributions of geopolymer samples,which in turn affected their compressive strength(σ).Duration of the ion exchange had no obvious effect on the sintered samples,and the amount of mullite phase increased with the increase in the sintering temperature.Mullite foams,possessing an open-celled porous structure,closely resembling that of the starting porous geopolymers produced by directly foaming,were obtained by firing at high temperatures.Stable mullite(3Al_(2)O_(3)·2SiO_(2))ceramic foams with total porosity(ε)of 83.52 vol%,high open porosity of 83.23 vol%,and compressive strength of 1.72 MPa were produced after sintering at 1400 for 2 h in℃ air without adding any sintering additives using commercial MK,bauxite,and FA as raw materials.
基金National Natural Science Foundation of China(11774057,11874286,61205041)Fundamental Research Funds for the Central Universities(20153638,22120190222)。
文摘The Pancharatnam–Berry geometric phase has attracted great interest due to the elegant phase control strategy via geometric transformation of optical elements.The commonly used geometric phase is associated with circular polarization states.Here,we show that by exploiting the geometric phase associated with the two elliptical eigenpolarization states in a racemic metallic helix array,exotic features including full range phase modulation for linear polarization states,diverse polarization conversion,and full complex amplitude modulation can be obtained with rotation of the helices.As a proof of concept,several devices for implementing polarization conversion,vortex beam generating,and lateral dual focusing are built with a racemic helix array in the microwave regime.The calculated and experimental results validate our proposals,which can stimulate various advanced metadevices.
基金supported by the National Natural Science Foundation of China(Grant Nos.91962109,42174094)the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(Grant No.2019QZKK0701)+1 种基金the Fund of Chinese Geological Survey(Grant No.DD20190016)the Basic Scientific Research Fund of the Institute of Geology,Chinese Academy of Geological Sciences(Grant No.J2015)。
文摘The North Himalayan gneiss domes(NHGD),as one of the extensional structures widely distributed across the southern Tibetan Plateau,are an important window for studying post-collisional diastrophism and magmation as well as polymetallic mineralization.However,the deep mechanism for the formation of NHGD remains controversial.The magnetotelluric(MT)method was adopted to study the deep structure of the Cuonadong dome in the Northern Himalayas.The characteristics of the dome were explored by using the MT sounding curves and phase tensors.Three-dimensional(3D)MT inversion was performed to determine the electrical resistivity structure beneath the Cuonadong dome.The preferred 3D electrical resistivity model shows that an obvious low-resistivity anomaly develops beneath the Cuonadong dome which is overlaid by a high-resistivity body and surrounded by an apparent subcircular zone of low-resistivity anomalies.The integrated conductivity(longitudinal conductance)from depths of 1-20 km indicates that the average longitudinal conductance at the core of the Cuonadong dome is about 10,000 S.The high-conductivity anomaly at the core is found to be analogous to that of lava,mainly resulting from the crustal partial melting,and the estimated melt content is 11.0-17.3%.The high conductance surrounding the dome reaches 20,000 S on average,which is mainly attributed to saline fluids.MT results in this study support that the Cuonadong dome experienced magmatic diapirism.Taken together with previous geological and geochemical studies,we suggest that under the east-west(E-W)extensional tectonic setting in southern Tibet,deep crustal partial melting constantly accumulated beneath the dome,and therefore the magmatic diapirism resulted in the formation of the Cuonadong dome.In addition,the MT results also indicate that the development of the Cuonadong dome provides abundant mineralizing fluids and the space for migration of metallogenic fluids for(rare-metal)polymetallic mineralization.
基金National Natural Science Foundation of China,Grant/Award Numbers:12074314,11774057,11674266,61771402NPU AoXiang New Star programScience,Technology and Innovation Commission of Shenzhen Municipality,Grant/Award Number:JCYJ20170817162221169。
文摘Since the performance of electronic circuits is becoming rather limited in face of intensively increasing of amount of information and related operations,alloptical processing offers a promising strategy for future information system.It would benefit a great deal if the all-optical processing could be implemented within the developed electronic chips of nanoscale structures.In that it is highly desirable to break the diffraction limit of light for achieving effective light manipulations with deep subwavelength structures compatible with the state-of-the-art nanofabrication processes.It is of fundamental importance to get subwavelength optical localization,that is,squeeze light wave into subwavelength space for achieving freely manipulating of light fields.This review summarizes the development in realizing subwavelength optical localization by exciting toroidal mode in photonic metamaterials.The toroidal excitations in plasmonic metamaterials and Mie resonant metamaterials,in 3D structures and planar metamaterials,with single or few layers in spectral regime from microwave to optical frequencies are surveyed.Based on the discussion on the configurations of toroidal excitations,the recent development on toroidalrelated optical scattering control actively manipulates the toroidal excitations,and promising applications are further investigated and highlighted.
基金This work was partly supported by the National Natural Science Foundation of China(Grant Nos.61235011,61008030,61108014,61205124)the ChenGuang Project of Shanghai Municipal Education Commission(Grant No.10CG19)+1 种基金the Specialized Research Fund for the Doctoral Program of High Education(Grant No.20100072120037)the National 863 Program.
文摘Thermomechanical damage of nodules in dielectric multilayer coatings that are irradiated by nanosecond laser pulses has been interpreted with respect to mechanical properties and electric-field enhancement.However,the effect of electric-field enhancement in nodular damage,especially the influence of electric-field distributions,has never been directly demonstrated through experimental results,which prevents the achievement of a clear understanding of the damage process of nodular defects.Here,a systematic and comparative study was designed to reveal how electric-field distributions affect the damage behavior of nodules.To obtain reliable results,two series of artificial nodules with different geometries and film absorption characteristics were prepared from monodisperse silica microspheres.After establishing simplified geometrical models of the nodules,the electric-field enhancement was simulated using a three-dimensional finite-difference time-domain code.Then,the damage morphologies of the artificial nodules were directly compared with the simulated electric-field intensity profiles.For both series of nodules,the damage morphologies reproduced our simulated electric-field intensity distributions very well.These results indicated that the electric-field distribution was actually a bridge that connected the nodular mechanical properties to the final thermomechanical damage.Understanding of the damage mechanism of nodules was deepened by obtaining data on the influence of electric-field distributions on the damage behavior of nodules.
基金This work was supported by the National Natural Science Foundation of China under grant nos.91123004,61390503,61475186 and 91023041,and XDB07020200by the Technical Talent Program of the Chinese Academy of Sciences.
文摘The application of three-dimensional(3D)plasmonic nanostructures as metamaterials(MMs),nano-antennas,and other devices faces challenges in producing metallic nanostructures with easily definable orientations,sophisticated shapes,and smooth surfaces that are operational in the optical regime and beyond.Here,we demonstrate that complex 3D nanostructures can be readily achieved with focused-ion-beam irradiation-induced folding and examine the optical characteristics of plasmonic“nanograter”structures that are composed of free-standing Au films.These 3D nanostructures exhibit interesting 3D hybridization in current flows and exhibit unusual and well-scalable Fano resonances at wavelengths ranging from 1.6 to 6.4 mm.Upon the introduction of liquids of various refractive indices to the structures,a strong dependence of the Fano resonance is observed,with spectral sensitivities of 1400 nm and 2040 nm per refractive index unit under figures of merit of 35.0 and 12.5,respectively,for low-order and high-order resonance in the near-infrared region.This work indicates the exciting,increasing relevance of similarly constructed 3D free-standing nanostructures in the research and development of photonics and MMs.
基金supported by the Science and Technology Project of the State Grid Corporation of China(No.5400-201935258A-0-0-00)the National Natural Science Foundation of China(No.51777104)
文摘With the increasing complexity of power system structures and the increasing penetration of renewable energy,the number of possible power system operation modes increases dramatically.It is difficult to make manual power flow adjustments to establish an initial convergent power flow that is suitable for operation mode analysis.At present,problems of low efficiency and long time consumption are encountered in the formulation of operation modes,resulting in a very limited number of generated operation modes.In this paper,we propose an intelligent power flow adjustment and generation model based on a deep network and reinforcement learning.First,a discriminator is trained to judge the power flow convergence,and the output of this discriminator is used to construct a value function.Then,the reinforcement learning method is adopted to learn a strategy for power flow convergence adjustment.Finally,a large number of convergent power flow samples are generated using the learned adjustment strategy.Compared with the traditional flow adjustment method,the proposed method has significant advantages that the learning of the power flow adjustment strategy does not depend on the parameters of the power system model.Therefore,this strategy can be automatically learned without manual intervention,which allows a large number of different operation modes to be efficiently formulated.The verification results of a case study show that the proposed method can independently learn a power flow adjustment strategy and generate various convergent power flows.
基金developed by the NLP601 group at School of Electronics Engineering and Computer Science, Peking University, within the National Natural Science Foundation of China (No. 61672046)
文摘Community Question Answering(CQA) in web forums, as a classic forum for user communication,provides a large number of high-quality useful answers in comparison with traditional question answering.Development of methods to get good, honest answers according to user questions is a challenging task in natural language processing. Many answers are not associated with the actual problem or shift the subjects,and this usually occurs in relatively long answers. In this paper, we enhance answer selection in CQA using multidimensional feature combination and similarity order. We make full use of the information in answers to questions to determine the similarity between questions and answers, and use the text-based description of the answer to determine whether it is a reasonable one. Our work includes two subtasks:(a) classifying answers as good, bad, or potentially associated with a question, and(b) answering YES/NO based on a list of all answers to a question. The experimental results show that our approach is significantly more efficient than the baseline model, and its overall ranking is relatively high in comparison with that of other models.
基金The authors thank the financial supports from the National Natural Science Foundation of China(Nos.51872005,52072002,and U1710116)the WanJiang Scholar Program.
文摘Heteroatom doping carbon materials exhibit a huge application potential for energy storage devices(ESDs).Herein,interconnected N/P co-doped carbon nanocage(NP-CNC)was synthesized from pyrene molecules by using nano-MgO as template and melamine-phytic acid supramolecular aggregate as dopant coupled with KOH activation.The as-prepared NP-CNC possesses interconnected nanocages for electron transportation and abundant micropores for ion adsorption.Moreover,co-doped N/P species in NP-CNC provide active sites and additional pseudocapacitance.Consequently,NP-CNC as electrode material for symmetric supercapacitor exhibits a high gravimetric capacitance of 435 F·g^(-1) at 0.05 A·g^(-1),high volumetric capacitance of 274 F·cm^(-3) at 0.032 A·cm^(-3),and long cycle lifespan with 96.1%capacitance retention after 50,000 cycles.Furthermore,NP-CNC as cathode for zinc-ion hybrid supercapacitor delivers satisfactory energy and power densities of 130.6 Wh·kg^(-1)(82.3 Wh·L^(-1))and 14.4 kW·kg^(-1)(9.1 kWL^(-1)).This work paves a promising approach to the preparation of high capacitance NP-CNC for ESDs.