Since Shuji Nakamura first demonstrated the nitride laser in 1996[1],the domain of semiconductor laser technology has undergone a period of remarkable growth[2,3].Al In Ga N-based diode lasers(LDs)have proven their ex...Since Shuji Nakamura first demonstrated the nitride laser in 1996[1],the domain of semiconductor laser technology has undergone a period of remarkable growth[2,3].Al In Ga N-based diode lasers(LDs)have proven their exceptional capabilities across a spectrum of pivotal applications,including high-density data storage,laser displays,laser lighting,and quantum technology[4].展开更多
A prototype of a laser driven proton accelerator is built at Peking University. Protons exceeding IOMeV are accelerated from micrometer-thick aluminum targets irradiated by tightly focused laser pulse with 1.8 J energ...A prototype of a laser driven proton accelerator is built at Peking University. Protons exceeding IOMeV are accelerated from micrometer-thick aluminum targets irradiated by tightly focused laser pulse with 1.8 J energy and 30fs duration. The beam energy spectrum and charge distribution are measured by a Thomson parabola spectrometer and radiochromic fihn stacks. The sensitivity of proton cut-off energy to the focusing of the laser beam, the pulse duration, and the foil thickness are systematically investigated in the experiments. Stable proton beams have been produced with an optimized parameter set, providing a cornerstone for the future applications of laser accelerated protons.展开更多
Purpose–The smoothness of the high-speed railway(HSR)on the bridge may exceed the allowable standard when an earthquake causes vibrations for HSR bridges,which may threaten the safety of running trains.Indeed,few stu...Purpose–The smoothness of the high-speed railway(HSR)on the bridge may exceed the allowable standard when an earthquake causes vibrations for HSR bridges,which may threaten the safety of running trains.Indeed,few studies have evaluated the exceeding probability of rail displacement exceeding the allowable standard.The purposes of this article are to provide a method for investigating the exceeding probability of the rail displacement of HSRs under seismic excitation and to calculate the exceeding probability.Design/methodology/approach–In order to investigate the exceeding probability of the rail displacement under different seismic excitations,the workflow of analyzing the smoothness of the rail based on incremental dynamic analysis(IDA)is proposed,and the intensity measure and limit state for the exceeding probability analysis of HSRs are defined.Then a finite element model(FEM)of an assumed HSR track-bridge system is constructed,which comprises a five-span simply-supported girder bridge supporting a finite length CRTS II ballastless track.Under different seismic excitations,the seismic displacement response of the rail is calculated;the character of the rail displacement is analyzed;and the exceeding probability of the rail vertical displacement exceeding the allowable standard(2mm)is investigated.Findings–The results show that:(1)The bridge-abutment joint position may form a step-like under seismic excitation,threatening the running safety of high-speed trains under seismic excitations,and the rail displacements at mid-span positions are bigger than that at other positions on the bridge.(2)The exceeding probability of rail displacement is up to about 44%when PGA 50.01g,which is the level-five risk probability and can be described as’very likely to happen’.(3)The exceeding probability of the rail at the mid-span positions is bigger than that above other positions of the bridge,and the mid-span positions of the track-bridge system above the bridge may be the most hazardous area for the running safety of trains under seismic excitation when high-speed trains run on bridges.Originality/value–The work extends the seismic hazardous analysis of HSRs and would lead to a better understanding of the exceeding probability for the rail of HSRs under seismic excitations and better references for the alert of the HSR operation.展开更多
The key project'Nano-scale catalyst and related process research and development activity for high-efficiency synthesis of mixed lower alcohols from syngas'undertaken by the Shanghai Senior Research Institute ...The key project'Nano-scale catalyst and related process research and development activity for high-efficiency synthesis of mixed lower alcohols from syngas'undertaken by the Shanghai Senior Research Institute of CAS has passed the acceptance tests by the expert group organized by the Shanghai Science and Technology Commission.展开更多
Shi Dazhen, Minister of the Power Industry, has announced that China’s power Construction had developed to a new level, exceeding 200 GW. He said that China’s power generating capacity reached 100 GW in 1987 and 199...Shi Dazhen, Minister of the Power Industry, has announced that China’s power Construction had developed to a new level, exceeding 200 GW. He said that China’s power generating capacity reached 100 GW in 1987 and 199.9 GW at the end of last year. As another two 60,000 kilowatts of power generation units went into operation in March, this year, power generating capacity reaches 200 GW in only seven years. Such a construction scale and展开更多
As the escalating trade dispute between China and the United States casts a shadow over the world＇s two largest economies andthe global economy at large, the much an ticipated Chinese economic figures for the first h...As the escalating trade dispute between China and the United States casts a shadow over the world＇s two largest economies andthe global economy at large, the much an ticipated Chinese economic figures for the first half of the year offer some certainty of China＇s economic resilience and sustainability.展开更多
For ages,scholars and engineers across the globe have been unceasing in their quest to unlock the mysteries of the 10,000-m-deep Earth,driven by the pursuit of new scientific theories and energy resources.On February ...For ages,scholars and engineers across the globe have been unceasing in their quest to unlock the mysteries of the 10,000-m-deep Earth,driven by the pursuit of new scientific theories and energy resources.On February 20,2025,China National Petroleum Corporation(CNPC)made a momentous announcement:China’s inaugural scientific exploration well at the 10,000-m level,the“Shenditake 1”well,nestled in the hinterland of the Taklimakan Desert in Xinjiang,was officially completed after reaching a staggering depth of 10,910 m beneath the surface.展开更多
With the rise of emerging applications such as artificial intelligence(AI),virtual reality(VR), and short videos, the number of Internet terminals has increased dramatically [1]. According to the Cisco Annual Traffic ...With the rise of emerging applications such as artificial intelligence(AI),virtual reality(VR), and short videos, the number of Internet terminals has increased dramatically [1]. According to the Cisco Annual Traffic Survey Report, annual traffic is growing at a compound annual growth rate of 20%[2]. To meet exploding growth in traffic demands, researchers have turned their attention to license-free high-band millimeter wave(MMW), such as W-band(75–110 GHz), D-band(110–170 GHz), and terahertz band(THz) [3,4].展开更多
Flexible perovskite solar cells(f-PSCs) have experienced rapid advancements due to the light-weight, flexibility, and solution processability of the perovskite materials, which prompted the power conversion efficiency...Flexible perovskite solar cells(f-PSCs) have experienced rapid advancements due to the light-weight, flexibility, and solution processability of the perovskite materials, which prompted the power conversion efficiency(PCE) to 24.08%. However, f-PSCs still face challenges in terms of mechanical and environmental stability. This is primarily due to their inherent brittleness, the presence of residual tensile strain, and the high density of defects along the boundaries of perovskite grains. To this end, we carefully developed a cross-linkable elastomers 3-[(3-acrylamidopropyl)dimethylammonium] propanoate(ADP) with electrostatic dynamic bond, which could be in-situ cross-linked and coordinate with [Pb I6]4-to regulate the crystallization process of perovskite. The cross-linked elastomers attached to the perovskite grain boundaries could release the remaining tensile strains and mechanical stresses, leading to enhanced stability and flexibility of the f-PSCs. More importantly, the electrostatic interaction between positive and negative groups of cross-linked elastomers and hydrogen bond formation between N–H and C=O accelerate the cross-linking of ADP, endowing the flexible perovskite films with self-healing ability under mild treating conditions(60 °C for 30 min). As a result, the device achieves a remarkable PCE of 23.53%(certified 23.16%). Additionally, the device exhibits impressive mechanical sustainability and durability, retaining over 90% of initial PCE even after undergoing8,000 bending cycles.展开更多
Nonreciprocal isolators enable unidirectional light propagation without back-reflection.Typical terahertz isolators require magnetic fields to break the time-reversal symmetry.Herein,we propose a nonmagnetic isolator ...Nonreciprocal isolators enable unidirectional light propagation without back-reflection.Typical terahertz isolators require magnetic fields to break the time-reversal symmetry.Herein,we propose a nonmagnetic isolator in the terahertz range based on nonreciprocal graphene plasmons operated in a reflection configuration.The bias voltage generates a drift current in graphene,which breaks the time-reversal symmetry and induces nonreciprocal reflection.The isolator device exhibited a high isolation exceeding 20 d B with an insertion loss of less than 3 d B.Moreover,the bandwidth wit isolation exceeding 20 d B can be broadened five times to 1.7 THz by tuning the carrier density.The indexes,including the isolation,insertion loss and bandwidth of the isolator,show a strong dependence on the drift velocity and mobility of graphene,as well as the air-gap thickness.Our study shows great potential in the burgeoning terahertz technology,where nonmagnetic and electrically tunable isolators are still lacking.展开更多
This letter describes the implementation of a high-precision time and frequency transmission system using a two-way and wavelength division multiplexing scheme over 3,143.6 km of field fiber links,connecting 21 sites ...This letter describes the implementation of a high-precision time and frequency transmission system using a two-way and wavelength division multiplexing scheme over 3,143.6 km of field fiber links,connecting 21 sites between Xi’an and Beijing,China.This scheme incorporates a link noise clean-up system(LNCUS),wherein a controlled very-low-phase noise BVA oscillator acts as an internal frequency source at the relay site to effectively suppress the interference caused by the fiber link noise.Additionally,the high-stability pulse generation technology in the LNCPS provides sufficient short-term stability to significantly improve the stability of the fiber time transfer.The results indicate a time transfer stability in terms of time deviation(TDEV)of less than2.07 ps@1s,5.9 ps@100,000s,and combined uncertainty of less than 49.29 ps for the 3,143.6 km field fiber link.The results represent a significant breakthrough in achieving high-accuracy time transfer and continuous operation over ultralong-span field optical fibers exceeding 3,000 km for the first time.This enabled time transfer and synchronization services over the longest international optical fiber distance,thereby establishing a fundamental basis for constructing a nationwide high-precision time service through optical fiber networks.展开更多
1 General information Journal of Geographical Sciences is an international academic journal that publishes papers of the highest quality in physical geography,natural resources,environmental sciences,geographic inform...1 General information Journal of Geographical Sciences is an international academic journal that publishes papers of the highest quality in physical geography,natural resources,environmental sciences,geographic information sciences,remote sensing and cartography.Manuscripts come from different parts of the world.2 Format and style Contributions should be typed on A4 paper using Times New Roman typeface in Word format,normally not exceeding 20,000 words.3 Abstract and keywords The text should be preceded by an abstract of 200-300 words,which should be followed by 3-7keywords on a separate line.展开更多
Polarization control and modulation of optical signals play a crucial role in optical information transmission,with widespread applications in optical communication,sensing,and signal processing.Here,we propose an int...Polarization control and modulation of optical signals play a crucial role in optical information transmission,with widespread applications in optical communication,sensing,and signal processing.Here,we propose an intrinsically chiral nano-kirigami metasurface featuring out-of-plane twisting,which enables switchable spinselective light transmission.At the operating wavelength,it nearly completely blocks the transmission of one type of circularly polarized light while maintaining a transmission exceeding 70%for the other type.Crucially,by merely adjusting the rotation angles or deformation heights of the four arms of the nano-kirigami structures,the metasurface can switch from selective transmission of left-handed circularly polarized light to right-handed circularly polarized light,and vice versa,without the need for dramatic structural geometric chirality changes through mirror operations.Simultaneously,a remarkable circular dichroism of up to 0.74 is achieved,and its sign reverses with the transition of transmission.Electromagnetic multipolar analysis reveals that this switching of chiral response is governed by handedness-dependent excitations of toroidal dipole modes.Additionally,the spin-encoded near-field imaging results demonstrate the potential applications of this switchable spin-selective transmission based on nano-kirigami metasurfaces in digital imaging and chiroptical encryption.展开更多
1 General information Journal of Geographical Sciences is an international academic journal that publishes papers of the highest quality in physical geography,natural resources,environmental sciences,geographic inform...1 General information Journal of Geographical Sciences is an international academic journal that publishes papers of the highest quality in physical geography,natural resources,environmental sciences,geographic information sciences,remote sensing and cartography.Manuscripts come from different parts of the world.2 Format and style Contributions should be typed on A4 paper using Times New Roman typeface in Word format,normally not exceeding 20,000 words.展开更多
Exciton diffusion lengths reaching the micrometer length scale have long been desired in solution-processed semiconductors but have remained unattainable using conventional materials to date.Now halide perovskite nano...Exciton diffusion lengths reaching the micrometer length scale have long been desired in solution-processed semiconductors but have remained unattainable using conventional materials to date.Now halide perovskite nanocrystal films show unprecedented exciton migration with diffusion lengths approaching 1μm owing to the efficient combination of radiative and nonradiative energy transfer.展开更多
We first established a method utilizing the oxygen isotope equilibration between water vapor and CO<sub>2</sub> gas catalyzed by a hot platinum filament at 1300°C for analysing oxygen isotope composit...We first established a method utilizing the oxygen isotope equilibration between water vapor and CO<sub>2</sub> gas catalyzed by a hot platinum filament at 1300°C for analysing oxygen isotope composition in China in 1982. It is especially suitable for simultaneously analysing H-O isotope composition of microliter water extracted from fluid inclusion according to our exoerience. The minimum ouantitv of water for this method is 2 μl. The water contents展开更多
Organic-inorganic hybrid perovskites possess a unique combination of excellent electronic and photoelectrochemical properties that can be readily tailored by partial or complete substitution of their constituent eleme...Organic-inorganic hybrid perovskites possess a unique combination of excellent electronic and photoelectrochemical properties that can be readily tailored by partial or complete substitution of their constituent elements owing to their nonclose packing anion lattice[1,2].Perovskite solar cells(PSCs)employing hybrid perovskites as an active layer have seen rapid improvements and have achieved high power conversion efficiencies(PCEs)now exceeding 25%[2].展开更多
To the editor:Food protein-induced enterocolitis syndrome(FPIES)is a non-immunoglobulin E-mediated food allergy that is characterized by repetitive vomiting within 1-4 h of eating the trigger food and may be associate...To the editor:Food protein-induced enterocolitis syndrome(FPIES)is a non-immunoglobulin E-mediated food allergy that is characterized by repetitive vomiting within 1-4 h of eating the trigger food and may be associated with lethargy,pallor,and diarrhea.The diagnosis is in most cases anamnestic.1 In a few cases,it is necessary to perform the oral food challenge(OFC).展开更多
Radial-Additive Friction Stir Repairing(R-AFSR),which has been developed in recent years for the exceeded tolerance hole,is an innovative technology to realize the one-step repairing.Enhancing the repair strength of e...Radial-Additive Friction Stir Repairing(R-AFSR),which has been developed in recent years for the exceeded tolerance hole,is an innovative technology to realize the one-step repairing.Enhancing the repair strength of exceeded tolerance hole is necessary and meaningful from the perspective of suiting more and more wide-scrapped equipment in the industrial field.UltrasonicAssisted R-AFSR(UA-RAFSR)is proposed as a strategy to achieve the 2024 aluminum(Al)alloy repaired hole with high strength.Analyses of microstructure formation indicate that the addition of ultrasonic eliminated the kissing bond and“S”line,refined the grain size,enlarged the interfacial bonding area and enhanced the atomic diffusion.Thus,the mechanical properties of 2024 Al alloy repaired hole were heightened by ultrasonic,and the maximum compressive shear and tensile strengths respectively reached 214.5 MPa and 297.3 MPa,which were 98.6% and 94.0% of those of the standard mechanical hole.The research results confirm that the UA-RAFSR is a powerful technology for the nearly-equal-strength repair of exceeded tolerance hole.展开更多
In the first quarter of 2019, despite complex and daunting conditions both at home and abroad, China continued to uphold the core principle of progress amidst stability. We remained committed to the new development ph...In the first quarter of 2019, despite complex and daunting conditions both at home and abroad, China continued to uphold the core principle of progress amidst stability. We remained committed to the new development philosophy, resolutely promoted high-quality growth by focusing on furthering structural reform on the supply side, and continued to fight the three critical battles against potential risks, poverty, and pollution. Thanks to these efforts, ChinaJs economic performance has maintained overall stability and exceeded expectations.展开更多
基金funded by the National Key Research and Development Program(Grant No.2023YFB4604400)the National Natural Science Foundation of China(Grant Nos.62225405,62350002,61991443)+2 种基金the Key R&D Program of Jiangsu ProvinceChina(Grant No.BE2020004)the Collaborative Innovation Centre of Solid-State Lighting and EnergySaving Electronics。
文摘Since Shuji Nakamura first demonstrated the nitride laser in 1996[1],the domain of semiconductor laser technology has undergone a period of remarkable growth[2,3].Al In Ga N-based diode lasers(LDs)have proven their exceptional capabilities across a spectrum of pivotal applications,including high-density data storage,laser displays,laser lighting,and quantum technology[4].
基金Supported by the National Basic Research Program of China under Grant No 2013CBA01502the National Natural Science Foundation of China under Grant Nos 11475010,11575011 and 11535001the National Grand Instrument Project under Grant No 2012YQ030142
文摘A prototype of a laser driven proton accelerator is built at Peking University. Protons exceeding IOMeV are accelerated from micrometer-thick aluminum targets irradiated by tightly focused laser pulse with 1.8 J energy and 30fs duration. The beam energy spectrum and charge distribution are measured by a Thomson parabola spectrometer and radiochromic fihn stacks. The sensitivity of proton cut-off energy to the focusing of the laser beam, the pulse duration, and the foil thickness are systematically investigated in the experiments. Stable proton beams have been produced with an optimized parameter set, providing a cornerstone for the future applications of laser accelerated protons.
基金supported by National Key Research and Development Plan of China“Basic Theory and Methods for Resilience Assessment and Risk Control of Transportation Infrastructures”(2021YFB2600500)the National Nature Science Foundation of Si Chuan(2023NSFSC0388)the Joint Research Fund for Earthquake Science launched by the National Natural Science Foundation of China and China Earthquake Administration(U2039208).
文摘Purpose–The smoothness of the high-speed railway(HSR)on the bridge may exceed the allowable standard when an earthquake causes vibrations for HSR bridges,which may threaten the safety of running trains.Indeed,few studies have evaluated the exceeding probability of rail displacement exceeding the allowable standard.The purposes of this article are to provide a method for investigating the exceeding probability of the rail displacement of HSRs under seismic excitation and to calculate the exceeding probability.Design/methodology/approach–In order to investigate the exceeding probability of the rail displacement under different seismic excitations,the workflow of analyzing the smoothness of the rail based on incremental dynamic analysis(IDA)is proposed,and the intensity measure and limit state for the exceeding probability analysis of HSRs are defined.Then a finite element model(FEM)of an assumed HSR track-bridge system is constructed,which comprises a five-span simply-supported girder bridge supporting a finite length CRTS II ballastless track.Under different seismic excitations,the seismic displacement response of the rail is calculated;the character of the rail displacement is analyzed;and the exceeding probability of the rail vertical displacement exceeding the allowable standard(2mm)is investigated.Findings–The results show that:(1)The bridge-abutment joint position may form a step-like under seismic excitation,threatening the running safety of high-speed trains under seismic excitations,and the rail displacements at mid-span positions are bigger than that at other positions on the bridge.(2)The exceeding probability of rail displacement is up to about 44%when PGA 50.01g,which is the level-five risk probability and can be described as’very likely to happen’.(3)The exceeding probability of the rail at the mid-span positions is bigger than that above other positions of the bridge,and the mid-span positions of the track-bridge system above the bridge may be the most hazardous area for the running safety of trains under seismic excitation when high-speed trains run on bridges.Originality/value–The work extends the seismic hazardous analysis of HSRs and would lead to a better understanding of the exceeding probability for the rail of HSRs under seismic excitations and better references for the alert of the HSR operation.
文摘The key project'Nano-scale catalyst and related process research and development activity for high-efficiency synthesis of mixed lower alcohols from syngas'undertaken by the Shanghai Senior Research Institute of CAS has passed the acceptance tests by the expert group organized by the Shanghai Science and Technology Commission.
文摘Shi Dazhen, Minister of the Power Industry, has announced that China’s power Construction had developed to a new level, exceeding 200 GW. He said that China’s power generating capacity reached 100 GW in 1987 and 199.9 GW at the end of last year. As another two 60,000 kilowatts of power generation units went into operation in March, this year, power generating capacity reaches 200 GW in only seven years. Such a construction scale and
文摘As the escalating trade dispute between China and the United States casts a shadow over the world＇s two largest economies andthe global economy at large, the much an ticipated Chinese economic figures for the first half of the year offer some certainty of China＇s economic resilience and sustainability.
文摘For ages,scholars and engineers across the globe have been unceasing in their quest to unlock the mysteries of the 10,000-m-deep Earth,driven by the pursuit of new scientific theories and energy resources.On February 20,2025,China National Petroleum Corporation(CNPC)made a momentous announcement:China’s inaugural scientific exploration well at the 10,000-m level,the“Shenditake 1”well,nestled in the hinterland of the Taklimakan Desert in Xinjiang,was officially completed after reaching a staggering depth of 10,910 m beneath the surface.
基金supported by the National Natural Science Foundation of China(Grant Nos.61935005, 61835002, 62305067, 62375219 and 62331004)the Natural Science Foundation of Shaanxi Province(Grant No.2023-JC-JQ-58)the Innovation Capability Support Program of Shaanxi(Grant No.2021TD-09)。
文摘With the rise of emerging applications such as artificial intelligence(AI),virtual reality(VR), and short videos, the number of Internet terminals has increased dramatically [1]. According to the Cisco Annual Traffic Survey Report, annual traffic is growing at a compound annual growth rate of 20%[2]. To meet exploding growth in traffic demands, researchers have turned their attention to license-free high-band millimeter wave(MMW), such as W-band(75–110 GHz), D-band(110–170 GHz), and terahertz band(THz) [3,4].
基金supported by the National Natural Science Foundation of China (U21A20331, 81903743, 22279151,22275004)the National Science Fund for Distinguished Young Scholars(21925506)。
文摘Flexible perovskite solar cells(f-PSCs) have experienced rapid advancements due to the light-weight, flexibility, and solution processability of the perovskite materials, which prompted the power conversion efficiency(PCE) to 24.08%. However, f-PSCs still face challenges in terms of mechanical and environmental stability. This is primarily due to their inherent brittleness, the presence of residual tensile strain, and the high density of defects along the boundaries of perovskite grains. To this end, we carefully developed a cross-linkable elastomers 3-[(3-acrylamidopropyl)dimethylammonium] propanoate(ADP) with electrostatic dynamic bond, which could be in-situ cross-linked and coordinate with [Pb I6]4-to regulate the crystallization process of perovskite. The cross-linked elastomers attached to the perovskite grain boundaries could release the remaining tensile strains and mechanical stresses, leading to enhanced stability and flexibility of the f-PSCs. More importantly, the electrostatic interaction between positive and negative groups of cross-linked elastomers and hydrogen bond formation between N–H and C=O accelerate the cross-linking of ADP, endowing the flexible perovskite films with self-healing ability under mild treating conditions(60 °C for 30 min). As a result, the device achieves a remarkable PCE of 23.53%(certified 23.16%). Additionally, the device exhibits impressive mechanical sustainability and durability, retaining over 90% of initial PCE even after undergoing8,000 bending cycles.
基金Supported by the National Natural Science Foundation of China(Grant Nos.11934011 and 12274365)National Key R&D Program of China(Grant Nos.2022YFA1402400 and 2022YFA1400043)+1 种基金Zhejiang Provincial Natural Science Foundation of China(Grant No.LR24A040001)Open project of Key Laboratory of Artificial Structures and Quantum Control(Ministry of Education)of Shanghai Jiao Tong University。
文摘Nonreciprocal isolators enable unidirectional light propagation without back-reflection.Typical terahertz isolators require magnetic fields to break the time-reversal symmetry.Herein,we propose a nonmagnetic isolator in the terahertz range based on nonreciprocal graphene plasmons operated in a reflection configuration.The bias voltage generates a drift current in graphene,which breaks the time-reversal symmetry and induces nonreciprocal reflection.The isolator device exhibited a high isolation exceeding 20 d B with an insertion loss of less than 3 d B.Moreover,the bandwidth wit isolation exceeding 20 d B can be broadened five times to 1.7 THz by tuning the carrier density.The indexes,including the isolation,insertion loss and bandwidth of the isolator,show a strong dependence on the drift velocity and mobility of graphene,as well as the air-gap thickness.Our study shows great potential in the burgeoning terahertz technology,where nonmagnetic and electrically tunable isolators are still lacking.
文摘This letter describes the implementation of a high-precision time and frequency transmission system using a two-way and wavelength division multiplexing scheme over 3,143.6 km of field fiber links,connecting 21 sites between Xi’an and Beijing,China.This scheme incorporates a link noise clean-up system(LNCUS),wherein a controlled very-low-phase noise BVA oscillator acts as an internal frequency source at the relay site to effectively suppress the interference caused by the fiber link noise.Additionally,the high-stability pulse generation technology in the LNCPS provides sufficient short-term stability to significantly improve the stability of the fiber time transfer.The results indicate a time transfer stability in terms of time deviation(TDEV)of less than2.07 ps@1s,5.9 ps@100,000s,and combined uncertainty of less than 49.29 ps for the 3,143.6 km field fiber link.The results represent a significant breakthrough in achieving high-accuracy time transfer and continuous operation over ultralong-span field optical fibers exceeding 3,000 km for the first time.This enabled time transfer and synchronization services over the longest international optical fiber distance,thereby establishing a fundamental basis for constructing a nationwide high-precision time service through optical fiber networks.
文摘1 General information Journal of Geographical Sciences is an international academic journal that publishes papers of the highest quality in physical geography,natural resources,environmental sciences,geographic information sciences,remote sensing and cartography.Manuscripts come from different parts of the world.2 Format and style Contributions should be typed on A4 paper using Times New Roman typeface in Word format,normally not exceeding 20,000 words.3 Abstract and keywords The text should be preceded by an abstract of 200-300 words,which should be followed by 3-7keywords on a separate line.
基金supported by the National Natural Science Foundation of China(Grant Nos.62205282 and 12074331)the Hebei Natural Science Foundation(Grant No.A2022203035)the Science and Technology Project of Hebei Education Department(Grant No.BJK2023009)。
文摘Polarization control and modulation of optical signals play a crucial role in optical information transmission,with widespread applications in optical communication,sensing,and signal processing.Here,we propose an intrinsically chiral nano-kirigami metasurface featuring out-of-plane twisting,which enables switchable spinselective light transmission.At the operating wavelength,it nearly completely blocks the transmission of one type of circularly polarized light while maintaining a transmission exceeding 70%for the other type.Crucially,by merely adjusting the rotation angles or deformation heights of the four arms of the nano-kirigami structures,the metasurface can switch from selective transmission of left-handed circularly polarized light to right-handed circularly polarized light,and vice versa,without the need for dramatic structural geometric chirality changes through mirror operations.Simultaneously,a remarkable circular dichroism of up to 0.74 is achieved,and its sign reverses with the transition of transmission.Electromagnetic multipolar analysis reveals that this switching of chiral response is governed by handedness-dependent excitations of toroidal dipole modes.Additionally,the spin-encoded near-field imaging results demonstrate the potential applications of this switchable spin-selective transmission based on nano-kirigami metasurfaces in digital imaging and chiroptical encryption.
文摘1 General information Journal of Geographical Sciences is an international academic journal that publishes papers of the highest quality in physical geography,natural resources,environmental sciences,geographic information sciences,remote sensing and cartography.Manuscripts come from different parts of the world.2 Format and style Contributions should be typed on A4 paper using Times New Roman typeface in Word format,normally not exceeding 20,000 words.
文摘Exciton diffusion lengths reaching the micrometer length scale have long been desired in solution-processed semiconductors but have remained unattainable using conventional materials to date.Now halide perovskite nanocrystal films show unprecedented exciton migration with diffusion lengths approaching 1μm owing to the efficient combination of radiative and nonradiative energy transfer.
文摘We first established a method utilizing the oxygen isotope equilibration between water vapor and CO<sub>2</sub> gas catalyzed by a hot platinum filament at 1300°C for analysing oxygen isotope composition in China in 1982. It is especially suitable for simultaneously analysing H-O isotope composition of microliter water extracted from fluid inclusion according to our exoerience. The minimum ouantitv of water for this method is 2 μl. The water contents
文摘Organic-inorganic hybrid perovskites possess a unique combination of excellent electronic and photoelectrochemical properties that can be readily tailored by partial or complete substitution of their constituent elements owing to their nonclose packing anion lattice[1,2].Perovskite solar cells(PSCs)employing hybrid perovskites as an active layer have seen rapid improvements and have achieved high power conversion efficiencies(PCEs)now exceeding 25%[2].
文摘To the editor:Food protein-induced enterocolitis syndrome(FPIES)is a non-immunoglobulin E-mediated food allergy that is characterized by repetitive vomiting within 1-4 h of eating the trigger food and may be associated with lethargy,pallor,and diarrhea.The diagnosis is in most cases anamnestic.1 In a few cases,it is necessary to perform the oral food challenge(OFC).
基金supported by the National Natural Science Foundation of China(Nos.51874201 and 52074184)the Fundamental Research Funds for the Universities of Liaoning Province,China(No.LJ222410143035)。
文摘Radial-Additive Friction Stir Repairing(R-AFSR),which has been developed in recent years for the exceeded tolerance hole,is an innovative technology to realize the one-step repairing.Enhancing the repair strength of exceeded tolerance hole is necessary and meaningful from the perspective of suiting more and more wide-scrapped equipment in the industrial field.UltrasonicAssisted R-AFSR(UA-RAFSR)is proposed as a strategy to achieve the 2024 aluminum(Al)alloy repaired hole with high strength.Analyses of microstructure formation indicate that the addition of ultrasonic eliminated the kissing bond and“S”line,refined the grain size,enlarged the interfacial bonding area and enhanced the atomic diffusion.Thus,the mechanical properties of 2024 Al alloy repaired hole were heightened by ultrasonic,and the maximum compressive shear and tensile strengths respectively reached 214.5 MPa and 297.3 MPa,which were 98.6% and 94.0% of those of the standard mechanical hole.The research results confirm that the UA-RAFSR is a powerful technology for the nearly-equal-strength repair of exceeded tolerance hole.
文摘In the first quarter of 2019, despite complex and daunting conditions both at home and abroad, China continued to uphold the core principle of progress amidst stability. We remained committed to the new development philosophy, resolutely promoted high-quality growth by focusing on furthering structural reform on the supply side, and continued to fight the three critical battles against potential risks, poverty, and pollution. Thanks to these efforts, ChinaJs economic performance has maintained overall stability and exceeded expectations.
