We successfully incorporated phenyl groups into a small-molecule quaternary ammonium cross-linker and synthesized cross-linked polybenzimidazole membranes via a one-step cross-linking process.Compared with conventiona...We successfully incorporated phenyl groups into a small-molecule quaternary ammonium cross-linker and synthesized cross-linked polybenzimidazole membranes via a one-step cross-linking process.Compared with conventional quaternary ammonium-crosslinked benzimidazole membranes,the introduction of phenyl groups significantly increases the free volume within the membrane.After phosphoric acid doping,the benzimidazole membrane with larger free volume retains more phosphoric acid compared to conventional quaternary ammonium-crosslinked membranes,forming an extensive hydrogen-bonding network that effectively enhances its anhydrous proton conductivity.The anhydrous proton conductivity reaches 91 mS·cm^(-1)at 160℃,substantially higher than that of conventional quaternary ammonium-crosslinked membranes with the same mass fraction.Benefiting from the improved conductivity,the membrane electrode assembly exhibits reduced ohmic polarization,achieving a peak power density of 792 mW·cm^(-2)at 160℃.展开更多
Cross-linkedβ-cyclodextrin polymer/Fe3O4 composite nanoparticles with core-shell structures were prepared via cross linking reaction on the surface of carboxymethylβ-cyclodextrin（CM-β-CD） modified Fe3O4 nanoparti...Cross-linkedβ-cyclodextrin polymer/Fe3O4 composite nanoparticles with core-shell structures were prepared via cross linking reaction on the surface of carboxymethylβ-cyclodextrin（CM-β-CD） modified Fe3O4 nanoparticles inβ-cyclodextrin alkaline solution by using epichlorohydrin as crosslinking agent.The morphology,structure and magnetic properties of the prepared composite nanoparticles were investigated by transmission electron microscopy（TEM）,Fourier transform infrared（FTIR） spectrometry,X-ray diffraction（XRD） measurement,thermogravimetric analysis（TGA） and Vibrating sample magnetometry （VSM）,respectively.展开更多
Cross-linked polyethylene (PEX) pipes used in hot water supply are required for high mechanical strength and high creep resistance at high temperature. Especially PEX-a pipes which are made by peroxide cross-linking h...Cross-linked polyethylene (PEX) pipes used in hot water supply are required for high mechanical strength and high creep resistance at high temperature. Especially PEX-a pipes which are made by peroxide cross-linking have better performance, such as creep resistance and thermal shock resistance than the pipes made by the other cross-linking method. Because the PEX-a pipes indicate the higher cross-link degree as compared with the other PEX pipes. In this study, the PEX-a pipes which were mixed with several stabilizers were tested to evaluate the effects on cross-link degree and the oxygen induction time. And also they are evaluated with the chlorine aqueous solution by the performance of the long-term hydrostatic pressure test and the long-term hydro dynamic pressure test. As a result, it was found that the combination of antioxidants for PEX-a pipes plays an important role to prolong the oxygen induction time without inhibiting the cross-linking. From the results of the 1H pulsed NMR measurement over the melting point of polyethylene, it was found that each peroxide PEX pipe with different antioxidant combinations indicated the different proportion and crosslink density of cross-linked region, in addition, that these pipes had the effective structure of cross-linking for the hydrostatic and hydrodynamic pressure test with the chlorine aqueous solution. Therefore, it was considered to be useful results for studies of the stricture of cross-linking of polyethylene.展开更多
Polyimide(PI)is a promising electronic packaging material,but it remains challenging to obtain an all-organic PI hybrid film with decreased dielectric constant and loss without modifying the monomer.Herein,a series of...Polyimide(PI)is a promising electronic packaging material,but it remains challenging to obtain an all-organic PI hybrid film with decreased dielectric constant and loss without modifying the monomer.Herein,a series of allorganic PI hybrid films were successfully prepared by introducing the covalent organic framework(COF),which could induce the formation of the cross-linking structure in the PI matrix.Due to the synergistic effects of the COF fillers and the cross-linking structure,the PI/COF hybrid film containing 2 wt%COF exhibited the lowest dielectric constant of 2.72 and the lowest dielectric loss(tanδ)of 0.0077 at 1 MHz.It is attributed to the intrinsic low dielectric constant of COF and a large number of mesopores within the PI.Besides,the cross-linking network of PI prevents the molecular chains from stacking and improves the fraction of free volume(FFV).The molecular dynamics simulation results are well consistent with the dielectric properties data.Furthermore,the PI/COF hybrid film with 5 wt%COF showed a significant enhancement in breakdown strength,which increased to 412.8 kV/mm as compared with pure PI.In addition,the PI/COF hybrid film achieve to reduce the dielectric constant and thermal expansion coefficient(CTE).It also exhibited excellent thermal,hydrophobicity,and mechanical performance.The all-organic PI/COF hybrid films have great commercial potential as next-generation electronic packaging materials.展开更多
Most reinforced concrete(RC)frame structures did not achieve the "strong column-weak beam" failure mode in recent big earthquakes, resulting in a large number of casualties and significant property loss. To ...Most reinforced concrete(RC)frame structures did not achieve the "strong column-weak beam" failure mode in recent big earthquakes, resulting in a large number of casualties and significant property loss. To deal with this serious problem, a new column-beam relative factor was proposed to characterize the relative yield situation of column ends and beam ends. By limiting the column-beam relative factor, RC frame structures could achieve the "strong column-weak beam" failure mode under the excitation of strong ground motions. The limit values of column-beam relative factor were calculated, analyzed and verified by using structural simulation models for corner columns in the bottom story of structures, which are destroyed most seriously in earthquakes. The results show that the limit values should be analyzed under bi-directional ground motion and with different axial compression ratios of columns. The peak ground acceleration(PGA)of ground motions has no significant effect on the limit values, while the type of strong ground motions has a significant effect on the limit values.展开更多
Inspired by nature's self-similar designs,novel honeycomb-spiderweb based self-similar hybrid cellular structures are proposed here for efficient energy absorption in impact applications.The energy absorption is e...Inspired by nature's self-similar designs,novel honeycomb-spiderweb based self-similar hybrid cellular structures are proposed here for efficient energy absorption in impact applications.The energy absorption is enhanced by optimizing the geometry and topology for a given mass.The proposed hybrid cellular structure is arrived after a thorough analysis of topologically enhanced self-similar structures.The optimized cell designs are rigorously tested considering dynamic loads involving crush and high-velocity bullet impact.Furthermore,the influence of thickness,radial connectivity,and order of patterning at the unit cell level are also investigated.The maximum crushing efficiency attained is found to be more than 95%,which is significantly higher than most existing traditional designs.Later on,the first and second-order hierarchical self-similar unit cell designs developed during crush analysis are used to prepare the cores for sandwich structures.Impact tests are performed on the developed sandwich structures using the standard 9-mm parabellum.The influence of multistaging on impact resistance is also investigated by maintaining a constant total thickness and mass of the sandwich structure.Moreover,in order to avoid layer-wise weak zones and hence,attain a uniform out-of-plane impact strength,off-setting the designs in each stage is proposed.The sandwich structures with first and second-order self-similar hybrid cores are observed to withstand impact velocities as high as 170 m/s and 270 m/s,respectively.展开更多
Properties and deformations of the rotating neutron stars in uniform strong magnetic field are calculated. The magnetic field will soften the equation of state of the neutron star matters and make an obvious effect on...Properties and deformations of the rotating neutron stars in uniform strong magnetic field are calculated. The magnetic field will soften the equation of state of the neutron star matters and make an obvious effect on the structure of the rotating neutron star. If the magnetic field is superstrong （B=10^17 T）, the mass, radius, and the deformation will become smaller effectively.展开更多
The present investigation is motivated by finding and developing an easily understandable solution in the context of unified quantum and gravitational theories. Model-based methods are applied, with emphasis on struct...The present investigation is motivated by finding and developing an easily understandable solution in the context of unified quantum and gravitational theories. Model-based methods are applied, with emphasis on structural descriptions by introducing some strong hypotheses. A subset of the introduced hypotheses led to a surprising understanding of the internal structure and construction of quarks, neutrons, protons and more complex atomic nuclei. The research work therefore focused mainly on the model-based interpretation of subatomic processes. The results obtained so far and presented in this paper are new. They consist of a generic description model for the structure of atomic nuclei. This model contains two important structural links that originate from the initial phase of the cosmological big bang. They hold atomic parts together and are involved in many known nuclear fusion and fission processes. Modifications of them, including the electron-positron annihilation process, are necessary and will be described. A new interpretation of the strong forces from the Standard Model is possible and will be given. In addition, the formation processes for electron and positron particles are considered. Based on the structural relationships, a deeper understanding of matter transformations (transmutations), early cosmological processes and dark matter has been achieved. All challenges of this work are the logical conclusions from the used hypotheses on two structural links. They need to be further investigated and verified by theoretical and experimental works. The postulated particle in this paper, as accompanying product in the electron-positron annihilation, will play a major role for the future investigations.展开更多
An analysis was conducted on the evolutional process of a mesoscale convective vortex （MCV） and associated heavy rainfall in the Dabie Mountain area on 21-22 June 2008,as well as their structural characteristics in ...An analysis was conducted on the evolutional process of a mesoscale convective vortex （MCV） and associated heavy rainfall in the Dabie Mountain area on 21-22 June 2008,as well as their structural characteristics in different stages,by using the mesoscale reanalysis data with 3 km and 1 h resolution generated by the Local Analysis and Prediction System （LAPS） in the Southern China Heavy Rainfall Experiment.The results showed that the latent heat released by convection in the midtroposphere was the main energy source for the development of a low-level vortex.There was a positive feedback interaction between the convection and the vortex,and the evolution of the MCV was closely related to the strength of the positive interaction.The most typical characteristics of the thermal structure in different stages were that,there was a relatively thin diabatic heating layer in the midtroposphere in the formative stage;the thickness of diabatic heating layer significantly increased in the mature stage;and it almost disappeared in the decay stage.The characteristics of the dynamic structure were that,in the formative stage,there was no anticyclonic circulation at the high level;in the mature stage,an anticyclonic circulation with strong divergence was formed at the high level;in the decay stage,the anticyclonic circulation was damaged and the high-level atmosphere was in a disordered state of turbulence.Finally,the structural schematics of the MCV in the formative and mature stage were established respectively.展开更多
Large-scale and low-cost preparation of carbon-based potassium anode with long life and high capacity is one of the footstones for the development of potassium ion batteries(PIBs).Herein,a low-cost carbon-based materi...Large-scale and low-cost preparation of carbon-based potassium anode with long life and high capacity is one of the footstones for the development of potassium ion batteries(PIBs).Herein,a low-cost carbon-based material,cross-linked hollow graphitic carbon(HGC),is large scale synthesized to apply for PIBs anode.Its hollow structure can afford sufficient space to overcome the damage caused by the volume expansion of graphitic carbon(GC).While the cross-linked structure forms a compact interconnection network that allows electrons to rapid transfer between different GC frameworks.Electrochemical measurements demonstrated that the HGC anode exhibited low charge/discharge plateau(about 0.25 V and 0.1 V)and excellent specific capacity as high as 298 m A h g^(-1)at the current density of 50 m A g^(-1).And more important,after 200 cycles the capacity of HGC anode still shows 269 m A h g^(-1)(the decay rate of per cycle is only 0.048%).Meanwhile,the use of commercial traditional electrolyte(KPF_(6))and cheap raw materials that provide new hope for trying and realizing the large-scale production of PIBs based on carbon anode materials.展开更多
Organic solar cells based on acceptor-p-acceptor(A-π-A) electron acceptors have attracted intensive attention due to their increasing and record power conversion efficiencies. To date, almost all of the reported A-π...Organic solar cells based on acceptor-p-acceptor(A-π-A) electron acceptors have attracted intensive attention due to their increasing and record power conversion efficiencies. To date, almost all of the reported A-π-A electron acceptors are based on aromatic p structures. Here, we have investigated the impact of anti-aromatization of the p-bridges on the optoelectronic properties of A-π-A electron acceptors by(time-dependent) density functional theory. Our calculations show that besides the frontier molecular orbitals corresponding to the aromatic p-bridge based acceptors("aromatic" acceptors),additional and unique occupied and unoccupied frontier orbitals are found for the acceptors based on the anti-aromatic p-bridges("anti-aromatic" acceptors). Moreover, by tuning isomeric structures of the p-bridges(e.g., fusion orientations or linking positions of thiophene moieties), the optical excitation energies for the transition between the additional occupied and unoccupied levels turn to be close to or substantially lower with respect to those for the transition between the "aromatic" frontier orbitals. The optical absorption of the "anti-aromatic" acceptors is thus either stronger or broader than the "aromatic"acceptors. Finally, the reorganization energies for electron transport are tunable and dependent on the p-bridge structures. These results indicate a great potential of "anti-aromatic" electron acceptors in organic photovoltaics.展开更多
Recently,Lee et al.claimed the experimental discovery of room-temperature ambient-pressure super-conductivity in a Cu-doped lead-apatite(LK-99)(arXiv:2307.12008,arXiv:2307.12037).Remarkably,the claimed superconductivi...Recently,Lee et al.claimed the experimental discovery of room-temperature ambient-pressure super-conductivity in a Cu-doped lead-apatite(LK-99)(arXiv:2307.12008,arXiv:2307.12037).Remarkably,the claimed superconductivity can persist up to 400 K at ambient pressure.Despite the experimental im-plication,the electronic structure of LK-99 has not yet been studied.Here,we investigate the electronic structures of LK-99 and its parent compound using first-principles calculations,aiming to elucidate the doping effects of Cu.Our results reveal that the parent compound Pb_(10)(PO_(4))_(6)O is an insulator,while Cu doping induces an insulator-metal transition and thus volume contraction.The band structures of LK-99 around the Fermi level are featured by a half-filled flat band and a fully-occupied flat band.These two very flat bands arise from both the 2p orbitals of 1/4-occupied O atoms and the hybridization of the 3d orbitals of Cu with the 2p orbitals of its nearest-neighboring O atoms.Interestingly,we observe four van Hove singularities on these two flat bands.Furthermore,we show that the flat band structures can be tuned by including electronic correlation effects or by doping different elements.We find that among the considered doping elements(Ni,Cu,Zn,Ag,and Au),both Ni and Zn doping result in the gap opening,whereas Au exhibits doping effects more similar to Cu than Ag.Our work establishes a foundation for fu-ture studies to investigate the role of unique electronic structures of LK-99 in its claimed superconducting properties.展开更多
Chitosan (CS) microparticles with and without cross-linking were prepared by a water-in-oil emulsion solvent diffusion method without any surfactants. Aqueous CS solution and ethyl ace- tate were used as water and oil...Chitosan (CS) microparticles with and without cross-linking were prepared by a water-in-oil emulsion solvent diffusion method without any surfactants. Aqueous CS solution and ethyl ace- tate were used as water and oil phases, respectively. Genipin was used as a cross-linker. Influ- ences of genipin ratios and cross-linking times on CS microparticle characteristics were investigated. Non-cross-linked and cross-linked CS microparticles were spherical in shape and rough in surface. Microparticle matrices showed porous structures. Surface roughness, mean par- ticle sizes and bulk density of CS microparticles increased and their dissolutions in acetic acid solution decreased when genipin ratio and cross- linking time increased.展开更多
The seismic data obtained from high resolution seismic refraction profile in Jiashi strong earthquake swarm area in Xinjiang, China were further processed with ray hit analysis method and more complete basement interf...The seismic data obtained from high resolution seismic refraction profile in Jiashi strong earthquake swarm area in Xinjiang, China were further processed with ray hit analysis method and more complete basement interface structural characteristics beneath Jiashi strong earthquake swarm area were determined. The results show that there are two clear basement interfaces at the upper crust in Jiashi strong earthquake swarm area. The first one with buried depth ranging from 2.6 km to 3.3 km presents integral and continuous structure, and it appears an inclined plane interface and smoothly rises up toward Tianshan Mountain. The second basement interface with buried depth from 8.5 km to 11.8 km, is the antiquated crystalline basement of Tarim basin. Near the post number of 37 km, the buried depth of the crystalline basement changed abruptly by 2.5 km, which maybe result from an ultra crystalline basement fault. If taking this fault as a boundary, the crystalline basement could be divided into two parts, i.e. the southwestern segment with buried depth about 11.5 km, and the northeastern segment with buried depth approxi-mately from 8.5 km to 9.0 km. That is to say, in each segment, the buried depth changes not too much. The northeast segment rises up as a whole and upheaves slightly from southwest to northeast, which reflects the upper crustal deformation characteristics under the special tectonic background at the northwestern edge of Tarim basin.展开更多
By means of the numerical renormalization group method, we study the phase transition, the spectral property, and the temperature-dependent magnetic moment for a parallel double dot system with level difference, where...By means of the numerical renormalization group method, we study the phase transition, the spectral property, and the temperature-dependent magnetic moment for a parallel double dot system with level difference, where the dot energies are kept symmetric to the half-filled level. A Kosterlitz–Thouless（KT） transition between local spin triplet and singlet is found. In the triplet regime, the local spin is partially screened by the conduction leads and spin-1 Kondo effect is realized.While for the singlet, the Kondo peak is strongly suppressed and the magnetic moment decreases to 0 at a definite low temperature. We attribute this KT transition to the breaking of the reflection symmetry, resulting from the difference of the charge occupations of the two dots. To understand this KT transition and related critical phenomena, detailed scenarios are given in the transmission coefficient and the magnetic moment, and an effective Kondo model refers to the RayleighSchrdinger perturbation theory is used.展开更多
<p align="justify"> <span style="font-family:Verdana;"><span style="font-family:Verdana;font-size:12px;">In this work, we extend our work on the Heisenberg model of the ...<p align="justify"> <span style="font-family:Verdana;"><span style="font-family:Verdana;font-size:12px;">In this work, we extend our work on the Heisenberg model of the neutron formulated as a dwarf hydrogen-like atom under the influence of the More General Exponential Screened Coulomb Potential (MGESCP) to show that an atomic nucleus may possess a molecular structure made up of atoms bonding together by a potential used to describe the strong force associated with a generalised Yukawa MGESCP potential. We show that the neutrons and protons are arranged into narrow lattices therefore they may fold to form three-dimensional shells by bonding similar to hydrogen bonding. In particular, the nucleons may form stable structures such as that of fullerenes in which the vertices are occupied by the nucleons which are simply just protons. For example, a nucleus with a total number of 60 nucleons may arrange itself into the topological structure of a buckminsterfullerene. We also apply </span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;font-size:12px;">Schr</span></span><span style="font-family:;"><span style="font-family:;font-size:12px;"></span><span style="text-align:left;widows:2;text-transform:none;background-color:#ffffff;font-style:normal;text-indent:0px;display:inline !important;font-family:Verdana;white-space:normal;orphans:2;float:none;letter-spacing:normal;font-size:12px;font-weight:400;word-spacing:0px;font-variant-ligatures:normal;font-variant-caps:normal;-webkit-text-stroke-width:0px;text-decoration-style:initial;text-decoration-color:initial;">ö</span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;font-size:12px;">dinger</span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;font-size:12px;"> wave equation with central field approximation to describe the quantum dynamics of nuclei of atomic atoms that now possess the physical structure of a dwarf molecular ion.</span></span> </p>展开更多
Lithium-ion batteries(LIBs)face significant limitations in low-temperature environments,with the slow interfacial de-solvation process and the hindered Li+transport through the interphase layer emerging as key obstacl...Lithium-ion batteries(LIBs)face significant limitations in low-temperature environments,with the slow interfacial de-solvation process and the hindered Li+transport through the interphase layer emerging as key obstacles beyond the issue of ionic conductivity.This investigation unveils a novel formulation that constructs an anion-rich solvation sheath within strong solvents,effectively addressing all three of these challenges to bolster low-temperature performance.The developed electrolyte,characterized by an enhanced concentration of contact ion pairs(CIPs)and aggregates(AGGs),facilitates the formation of an inorganic-rich interphase layer on the anode and cathode particles.This promotes de-solvation at low temperatures and stabilizes the electrode-electrolyte interphase.Full cells composed of LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)(NCM622)and graphite,when equipped with this electrolyte,showcase remarkable cycle stability and capacity retention,with 93.3% retention after 500 cycles at room temperature(RT)and 95.5%after 120 cycles at -20℃.This study validates the utility of the anion-rich solvation sheath in strong solvents as a strategy for the development of low-temperature electrolytes.展开更多
The use of dynamic programming(DP)algorithms to learn Bayesian network structures is limited by their high space complexity and difficulty in learning the structure of large-scale networks.Therefore,this study propose...The use of dynamic programming(DP)algorithms to learn Bayesian network structures is limited by their high space complexity and difficulty in learning the structure of large-scale networks.Therefore,this study proposes a DP algorithm based on node block sequence constraints.The proposed algorithm constrains the traversal process of the parent graph by using the M-sequence matrix to considerably reduce the time consumption and space complexity by pruning the traversal process of the order graph using the node block sequence.Experimental results show that compared with existing DP algorithms,the proposed algorithm can obtain learning results more efficiently with less than 1%loss of accuracy,and can be used for learning larger-scale networks.展开更多
基金Funded in part by the National Key Research and Development Program of China(No.2023YFB4006302)。
文摘We successfully incorporated phenyl groups into a small-molecule quaternary ammonium cross-linker and synthesized cross-linked polybenzimidazole membranes via a one-step cross-linking process.Compared with conventional quaternary ammonium-crosslinked benzimidazole membranes,the introduction of phenyl groups significantly increases the free volume within the membrane.After phosphoric acid doping,the benzimidazole membrane with larger free volume retains more phosphoric acid compared to conventional quaternary ammonium-crosslinked membranes,forming an extensive hydrogen-bonding network that effectively enhances its anhydrous proton conductivity.The anhydrous proton conductivity reaches 91 mS·cm^(-1)at 160℃,substantially higher than that of conventional quaternary ammonium-crosslinked membranes with the same mass fraction.Benefiting from the improved conductivity,the membrane electrode assembly exhibits reduced ohmic polarization,achieving a peak power density of 792 mW·cm^(-2)at 160℃.
基金financially supported by the Guangdong Natural Science Foundation(No.020891)
文摘Cross-linkedβ-cyclodextrin polymer/Fe3O4 composite nanoparticles with core-shell structures were prepared via cross linking reaction on the surface of carboxymethylβ-cyclodextrin（CM-β-CD） modified Fe3O4 nanoparticles inβ-cyclodextrin alkaline solution by using epichlorohydrin as crosslinking agent.The morphology,structure and magnetic properties of the prepared composite nanoparticles were investigated by transmission electron microscopy（TEM）,Fourier transform infrared（FTIR） spectrometry,X-ray diffraction（XRD） measurement,thermogravimetric analysis（TGA） and Vibrating sample magnetometry （VSM）,respectively.
文摘Cross-linked polyethylene (PEX) pipes used in hot water supply are required for high mechanical strength and high creep resistance at high temperature. Especially PEX-a pipes which are made by peroxide cross-linking have better performance, such as creep resistance and thermal shock resistance than the pipes made by the other cross-linking method. Because the PEX-a pipes indicate the higher cross-link degree as compared with the other PEX pipes. In this study, the PEX-a pipes which were mixed with several stabilizers were tested to evaluate the effects on cross-link degree and the oxygen induction time. And also they are evaluated with the chlorine aqueous solution by the performance of the long-term hydrostatic pressure test and the long-term hydro dynamic pressure test. As a result, it was found that the combination of antioxidants for PEX-a pipes plays an important role to prolong the oxygen induction time without inhibiting the cross-linking. From the results of the 1H pulsed NMR measurement over the melting point of polyethylene, it was found that each peroxide PEX pipe with different antioxidant combinations indicated the different proportion and crosslink density of cross-linked region, in addition, that these pipes had the effective structure of cross-linking for the hydrostatic and hydrodynamic pressure test with the chlorine aqueous solution. Therefore, it was considered to be useful results for studies of the stricture of cross-linking of polyethylene.
基金supported by National Natural Science Foundation of China(52103029 and 51903075).
文摘Polyimide(PI)is a promising electronic packaging material,but it remains challenging to obtain an all-organic PI hybrid film with decreased dielectric constant and loss without modifying the monomer.Herein,a series of allorganic PI hybrid films were successfully prepared by introducing the covalent organic framework(COF),which could induce the formation of the cross-linking structure in the PI matrix.Due to the synergistic effects of the COF fillers and the cross-linking structure,the PI/COF hybrid film containing 2 wt%COF exhibited the lowest dielectric constant of 2.72 and the lowest dielectric loss(tanδ)of 0.0077 at 1 MHz.It is attributed to the intrinsic low dielectric constant of COF and a large number of mesopores within the PI.Besides,the cross-linking network of PI prevents the molecular chains from stacking and improves the fraction of free volume(FFV).The molecular dynamics simulation results are well consistent with the dielectric properties data.Furthermore,the PI/COF hybrid film with 5 wt%COF showed a significant enhancement in breakdown strength,which increased to 412.8 kV/mm as compared with pure PI.In addition,the PI/COF hybrid film achieve to reduce the dielectric constant and thermal expansion coefficient(CTE).It also exhibited excellent thermal,hydrophobicity,and mechanical performance.The all-organic PI/COF hybrid films have great commercial potential as next-generation electronic packaging materials.
基金Supported by the National Natural Science Foundation of China(No.51525803)the Scientific and Technological Development Plans of Tianjin Construction System(No.2013-35)+1 种基金International Science&Technology Cooperation Program of China(No.2012DFA70810)the Basic Science Research Foundation of IEM,CEA(No.2013B07)
文摘Most reinforced concrete(RC)frame structures did not achieve the "strong column-weak beam" failure mode in recent big earthquakes, resulting in a large number of casualties and significant property loss. To deal with this serious problem, a new column-beam relative factor was proposed to characterize the relative yield situation of column ends and beam ends. By limiting the column-beam relative factor, RC frame structures could achieve the "strong column-weak beam" failure mode under the excitation of strong ground motions. The limit values of column-beam relative factor were calculated, analyzed and verified by using structural simulation models for corner columns in the bottom story of structures, which are destroyed most seriously in earthquakes. The results show that the limit values should be analyzed under bi-directional ground motion and with different axial compression ratios of columns. The peak ground acceleration(PGA)of ground motions has no significant effect on the limit values, while the type of strong ground motions has a significant effect on the limit values.
基金the Science and Engineering Research Board(SERB),Department of Science and Technology,India,for funding this research through grant number SRG/2019/001581。
文摘Inspired by nature's self-similar designs,novel honeycomb-spiderweb based self-similar hybrid cellular structures are proposed here for efficient energy absorption in impact applications.The energy absorption is enhanced by optimizing the geometry and topology for a given mass.The proposed hybrid cellular structure is arrived after a thorough analysis of topologically enhanced self-similar structures.The optimized cell designs are rigorously tested considering dynamic loads involving crush and high-velocity bullet impact.Furthermore,the influence of thickness,radial connectivity,and order of patterning at the unit cell level are also investigated.The maximum crushing efficiency attained is found to be more than 95%,which is significantly higher than most existing traditional designs.Later on,the first and second-order hierarchical self-similar unit cell designs developed during crush analysis are used to prepare the cores for sandwich structures.Impact tests are performed on the developed sandwich structures using the standard 9-mm parabellum.The influence of multistaging on impact resistance is also investigated by maintaining a constant total thickness and mass of the sandwich structure.Moreover,in order to avoid layer-wise weak zones and hence,attain a uniform out-of-plane impact strength,off-setting the designs in each stage is proposed.The sandwich structures with first and second-order self-similar hybrid cores are observed to withstand impact velocities as high as 170 m/s and 270 m/s,respectively.
基金The project supported by National Natural Science Foundation of China under Grant Nos. 10647116 and 10575140 and the China Postdoctoral Science Foundation under Grant No. 2005037175
文摘Properties and deformations of the rotating neutron stars in uniform strong magnetic field are calculated. The magnetic field will soften the equation of state of the neutron star matters and make an obvious effect on the structure of the rotating neutron star. If the magnetic field is superstrong （B=10^17 T）, the mass, radius, and the deformation will become smaller effectively.
文摘The present investigation is motivated by finding and developing an easily understandable solution in the context of unified quantum and gravitational theories. Model-based methods are applied, with emphasis on structural descriptions by introducing some strong hypotheses. A subset of the introduced hypotheses led to a surprising understanding of the internal structure and construction of quarks, neutrons, protons and more complex atomic nuclei. The research work therefore focused mainly on the model-based interpretation of subatomic processes. The results obtained so far and presented in this paper are new. They consist of a generic description model for the structure of atomic nuclei. This model contains two important structural links that originate from the initial phase of the cosmological big bang. They hold atomic parts together and are involved in many known nuclear fusion and fission processes. Modifications of them, including the electron-positron annihilation process, are necessary and will be described. A new interpretation of the strong forces from the Standard Model is possible and will be given. In addition, the formation processes for electron and positron particles are considered. Based on the structural relationships, a deeper understanding of matter transformations (transmutations), early cosmological processes and dark matter has been achieved. All challenges of this work are the logical conclusions from the used hypotheses on two structural links. They need to be further investigated and verified by theoretical and experimental works. The postulated particle in this paper, as accompanying product in the electron-positron annihilation, will play a major role for the future investigations.
基金supported by the state "973" project "Research on Theories and Methods of Monitoring and Predicting of Heavy Rainfall in South China" (Grant No. 2004CB418300)
文摘An analysis was conducted on the evolutional process of a mesoscale convective vortex （MCV） and associated heavy rainfall in the Dabie Mountain area on 21-22 June 2008,as well as their structural characteristics in different stages,by using the mesoscale reanalysis data with 3 km and 1 h resolution generated by the Local Analysis and Prediction System （LAPS） in the Southern China Heavy Rainfall Experiment.The results showed that the latent heat released by convection in the midtroposphere was the main energy source for the development of a low-level vortex.There was a positive feedback interaction between the convection and the vortex,and the evolution of the MCV was closely related to the strength of the positive interaction.The most typical characteristics of the thermal structure in different stages were that,there was a relatively thin diabatic heating layer in the midtroposphere in the formative stage;the thickness of diabatic heating layer significantly increased in the mature stage;and it almost disappeared in the decay stage.The characteristics of the dynamic structure were that,in the formative stage,there was no anticyclonic circulation at the high level;in the mature stage,an anticyclonic circulation with strong divergence was formed at the high level;in the decay stage,the anticyclonic circulation was damaged and the high-level atmosphere was in a disordered state of turbulence.Finally,the structural schematics of the MCV in the formative and mature stage were established respectively.
基金financially supported by National Natural Science Foundation of China(Nos.51922038 and 51672078)Hunan Outstanding Youth Talents(No.2019JJ20005)
文摘Large-scale and low-cost preparation of carbon-based potassium anode with long life and high capacity is one of the footstones for the development of potassium ion batteries(PIBs).Herein,a low-cost carbon-based material,cross-linked hollow graphitic carbon(HGC),is large scale synthesized to apply for PIBs anode.Its hollow structure can afford sufficient space to overcome the damage caused by the volume expansion of graphitic carbon(GC).While the cross-linked structure forms a compact interconnection network that allows electrons to rapid transfer between different GC frameworks.Electrochemical measurements demonstrated that the HGC anode exhibited low charge/discharge plateau(about 0.25 V and 0.1 V)and excellent specific capacity as high as 298 m A h g^(-1)at the current density of 50 m A g^(-1).And more important,after 200 cycles the capacity of HGC anode still shows 269 m A h g^(-1)(the decay rate of per cycle is only 0.048%).Meanwhile,the use of commercial traditional electrolyte(KPF_(6))and cheap raw materials that provide new hope for trying and realizing the large-scale production of PIBs based on carbon anode materials.
基金financially supported by the National Natural Science Foundation of China (No. 51773208)the Ministry of Science and Technology of China (No. 2014CB643506)the Strategic Priority Research Program of the Chinese Academy of Sciences (No. XDB12020200).
文摘Organic solar cells based on acceptor-p-acceptor(A-π-A) electron acceptors have attracted intensive attention due to their increasing and record power conversion efficiencies. To date, almost all of the reported A-π-A electron acceptors are based on aromatic p structures. Here, we have investigated the impact of anti-aromatization of the p-bridges on the optoelectronic properties of A-π-A electron acceptors by(time-dependent) density functional theory. Our calculations show that besides the frontier molecular orbitals corresponding to the aromatic p-bridge based acceptors("aromatic" acceptors),additional and unique occupied and unoccupied frontier orbitals are found for the acceptors based on the anti-aromatic p-bridges("anti-aromatic" acceptors). Moreover, by tuning isomeric structures of the p-bridges(e.g., fusion orientations or linking positions of thiophene moieties), the optical excitation energies for the transition between the additional occupied and unoccupied levels turn to be close to or substantially lower with respect to those for the transition between the "aromatic" frontier orbitals. The optical absorption of the "anti-aromatic" acceptors is thus either stronger or broader than the "aromatic"acceptors. Finally, the reorganization energies for electron transport are tunable and dependent on the p-bridge structures. These results indicate a great potential of "anti-aromatic" electron acceptors in organic photovoltaics.
文摘Recently,Lee et al.claimed the experimental discovery of room-temperature ambient-pressure super-conductivity in a Cu-doped lead-apatite(LK-99)(arXiv:2307.12008,arXiv:2307.12037).Remarkably,the claimed superconductivity can persist up to 400 K at ambient pressure.Despite the experimental im-plication,the electronic structure of LK-99 has not yet been studied.Here,we investigate the electronic structures of LK-99 and its parent compound using first-principles calculations,aiming to elucidate the doping effects of Cu.Our results reveal that the parent compound Pb_(10)(PO_(4))_(6)O is an insulator,while Cu doping induces an insulator-metal transition and thus volume contraction.The band structures of LK-99 around the Fermi level are featured by a half-filled flat band and a fully-occupied flat band.These two very flat bands arise from both the 2p orbitals of 1/4-occupied O atoms and the hybridization of the 3d orbitals of Cu with the 2p orbitals of its nearest-neighboring O atoms.Interestingly,we observe four van Hove singularities on these two flat bands.Furthermore,we show that the flat band structures can be tuned by including electronic correlation effects or by doping different elements.We find that among the considered doping elements(Ni,Cu,Zn,Ag,and Au),both Ni and Zn doping result in the gap opening,whereas Au exhibits doping effects more similar to Cu than Ag.Our work establishes a foundation for fu-ture studies to investigate the role of unique electronic structures of LK-99 in its claimed superconducting properties.
文摘Chitosan (CS) microparticles with and without cross-linking were prepared by a water-in-oil emulsion solvent diffusion method without any surfactants. Aqueous CS solution and ethyl ace- tate were used as water and oil phases, respectively. Genipin was used as a cross-linker. Influ- ences of genipin ratios and cross-linking times on CS microparticle characteristics were investigated. Non-cross-linked and cross-linked CS microparticles were spherical in shape and rough in surface. Microparticle matrices showed porous structures. Surface roughness, mean par- ticle sizes and bulk density of CS microparticles increased and their dissolutions in acetic acid solution decreased when genipin ratio and cross- linking time increased.
基金Foundation item: Joint Seismological Foundation of China (106076)National Natural Science Foundation of China (40474049, 40334040).
文摘The seismic data obtained from high resolution seismic refraction profile in Jiashi strong earthquake swarm area in Xinjiang, China were further processed with ray hit analysis method and more complete basement interface structural characteristics beneath Jiashi strong earthquake swarm area were determined. The results show that there are two clear basement interfaces at the upper crust in Jiashi strong earthquake swarm area. The first one with buried depth ranging from 2.6 km to 3.3 km presents integral and continuous structure, and it appears an inclined plane interface and smoothly rises up toward Tianshan Mountain. The second basement interface with buried depth from 8.5 km to 11.8 km, is the antiquated crystalline basement of Tarim basin. Near the post number of 37 km, the buried depth of the crystalline basement changed abruptly by 2.5 km, which maybe result from an ultra crystalline basement fault. If taking this fault as a boundary, the crystalline basement could be divided into two parts, i.e. the southwestern segment with buried depth about 11.5 km, and the northeastern segment with buried depth approxi-mately from 8.5 km to 9.0 km. That is to say, in each segment, the buried depth changes not too much. The northeast segment rises up as a whole and upheaves slightly from southwest to northeast, which reflects the upper crustal deformation characteristics under the special tectonic background at the northwestern edge of Tarim basin.
基金supported by the National Natural Science Foundation of China(Grant No.11504102)the Special Fund for Theoretical Physics of the National Natural Science Foundation of China(Grant No.11647133)+1 种基金the Doctoral Scientific Research Foundation of China(Grant No.BK201407)the Major Scientific Research Project Pre-funds of Hubei University of Automotive Technology,China(Grant No.2014XY06)
文摘By means of the numerical renormalization group method, we study the phase transition, the spectral property, and the temperature-dependent magnetic moment for a parallel double dot system with level difference, where the dot energies are kept symmetric to the half-filled level. A Kosterlitz–Thouless（KT） transition between local spin triplet and singlet is found. In the triplet regime, the local spin is partially screened by the conduction leads and spin-1 Kondo effect is realized.While for the singlet, the Kondo peak is strongly suppressed and the magnetic moment decreases to 0 at a definite low temperature. We attribute this KT transition to the breaking of the reflection symmetry, resulting from the difference of the charge occupations of the two dots. To understand this KT transition and related critical phenomena, detailed scenarios are given in the transmission coefficient and the magnetic moment, and an effective Kondo model refers to the RayleighSchrdinger perturbation theory is used.
文摘<p align="justify"> <span style="font-family:Verdana;"><span style="font-family:Verdana;font-size:12px;">In this work, we extend our work on the Heisenberg model of the neutron formulated as a dwarf hydrogen-like atom under the influence of the More General Exponential Screened Coulomb Potential (MGESCP) to show that an atomic nucleus may possess a molecular structure made up of atoms bonding together by a potential used to describe the strong force associated with a generalised Yukawa MGESCP potential. We show that the neutrons and protons are arranged into narrow lattices therefore they may fold to form three-dimensional shells by bonding similar to hydrogen bonding. In particular, the nucleons may form stable structures such as that of fullerenes in which the vertices are occupied by the nucleons which are simply just protons. For example, a nucleus with a total number of 60 nucleons may arrange itself into the topological structure of a buckminsterfullerene. We also apply </span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;font-size:12px;">Schr</span></span><span style="font-family:;"><span style="font-family:;font-size:12px;"></span><span style="text-align:left;widows:2;text-transform:none;background-color:#ffffff;font-style:normal;text-indent:0px;display:inline !important;font-family:Verdana;white-space:normal;orphans:2;float:none;letter-spacing:normal;font-size:12px;font-weight:400;word-spacing:0px;font-variant-ligatures:normal;font-variant-caps:normal;-webkit-text-stroke-width:0px;text-decoration-style:initial;text-decoration-color:initial;">ö</span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;font-size:12px;">dinger</span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;font-size:12px;"> wave equation with central field approximation to describe the quantum dynamics of nuclei of atomic atoms that now possess the physical structure of a dwarf molecular ion.</span></span> </p>
基金the National Natural Science Foundation of China(No.22279070[L.Wang]and U21A20170[X.He])the Ministry of Science and Technology of China(No.2019YFA0705703[L.Wang])。
文摘Lithium-ion batteries(LIBs)face significant limitations in low-temperature environments,with the slow interfacial de-solvation process and the hindered Li+transport through the interphase layer emerging as key obstacles beyond the issue of ionic conductivity.This investigation unveils a novel formulation that constructs an anion-rich solvation sheath within strong solvents,effectively addressing all three of these challenges to bolster low-temperature performance.The developed electrolyte,characterized by an enhanced concentration of contact ion pairs(CIPs)and aggregates(AGGs),facilitates the formation of an inorganic-rich interphase layer on the anode and cathode particles.This promotes de-solvation at low temperatures and stabilizes the electrode-electrolyte interphase.Full cells composed of LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)(NCM622)and graphite,when equipped with this electrolyte,showcase remarkable cycle stability and capacity retention,with 93.3% retention after 500 cycles at room temperature(RT)and 95.5%after 120 cycles at -20℃.This study validates the utility of the anion-rich solvation sheath in strong solvents as a strategy for the development of low-temperature electrolytes.
基金Shaanxi Science Fund for Distinguished Young Scholars,Grant/Award Number:2024JC-JCQN-57Xi’an Science and Technology Plan Project,Grant/Award Number:2023JH-QCYJQ-0086+2 种基金Scientific Research Program Funded by Education Department of Shaanxi Provincial Government,Grant/Award Number:P23JP071Engineering Technology Research Center of Shaanxi Province for Intelligent Testing and Reliability Evaluation of Electronic Equipments,Grant/Award Number:2023-ZC-GCZX-00472022 Shaanxi University Youth Innovation Team Project。
文摘The use of dynamic programming(DP)algorithms to learn Bayesian network structures is limited by their high space complexity and difficulty in learning the structure of large-scale networks.Therefore,this study proposes a DP algorithm based on node block sequence constraints.The proposed algorithm constrains the traversal process of the parent graph by using the M-sequence matrix to considerably reduce the time consumption and space complexity by pruning the traversal process of the order graph using the node block sequence.Experimental results show that compared with existing DP algorithms,the proposed algorithm can obtain learning results more efficiently with less than 1%loss of accuracy,and can be used for learning larger-scale networks.
