This study empirically examines how land finance in destination and origin cities affects willingness to engage in labor mobility and explores the underlying mechanisms.Using a two-way fixed effects model,we match mac...This study empirically examines how land finance in destination and origin cities affects willingness to engage in labor mobility and explores the underlying mechanisms.Using a two-way fixed effects model,we match macro data from 287 prefecture-level cities in China from 2000 to 2020 with data from the 2018 China Migrant Dynamic Survey(CMDS).The results are as follows:First,land finance in destination cities inhibits labor mobility willingness,while land finance in origin cities and labor mobility willingness have a U-shaped relationship,decreasing initially and then increasing.Second,local governments’dependence on land finance increases local housing prices and suppresses investment in non-economic public goods in the administrative area,thereby inhibiting labor mobility willingness;however,this also increases investment in economic public goods,attracting labor mobility willingness.Third,labor force age weakens the impact of land finance in origin cities on labor mobility willingness;however,age does not affect the impact of land finance in destination cities on labor mobility willingness.Fourth,land finance increases laborers’willingness to settle.展开更多
The technological advancement of the vehicular Internet ofThings(IoT)has revolutionized Intelligent Transportation Systems(ITS)into next-generation ITS.The connectivity of IoT nodes enables improved data availability ...The technological advancement of the vehicular Internet ofThings(IoT)has revolutionized Intelligent Transportation Systems(ITS)into next-generation ITS.The connectivity of IoT nodes enables improved data availability and facilitates automatic control in the ITS environment.The exponential increase in IoT nodes has significantly increased the demand for an energy-efficient,mobility-aware,and secure system for distributed intelligence.This article presents a mobility-aware Deep Reinforcement Learning based Federated Learning(DRL-FL)approach to design an energy-efficient and threat-resilient ITS.In this approach,a Policy Proximal Optimization(PPO)-based DRL agent is first employed for adaptive client selection.Second,an autoencoder-based anomaly detectionmodule is considered for malicious node detection.Results reveal that the proposed framework achieved an 8%higher accuracy increase,and 15%lower energy consumption.Themodel also demonstrates greater resilience under adversarial conditions compared to the state of the art in federated learning.The adaptability of the proposed approach makes it a compelling choice for next-generation vehicular networks.展开更多
Bilayer MoS2 is a promising channel candidate for extending Moore’s law,owing to its optimal channel thickness and improved suppression of extrinsic scattering compared to monolayers.However,its intrinsic phonon-limi...Bilayer MoS2 is a promising channel candidate for extending Moore’s law,owing to its optimal channel thickness and improved suppression of extrinsic scattering compared to monolayers.However,its intrinsic phonon-limited electron mobility is severely limited by enhanced K–Q intervalley scattering arising from the multivalley conduction band feature inherent to the bilayer structure.To overcome this bottleneck,we propose a“valley separation engineering”strategy that combines a twist angle near 30°with applied stress.Our first-principles calculations demonstrate that although valley separation can be continuously increased using this strategy,the electron mobility saturates at∼200 cm^(2)⋅V^(−1)⋅s^(−1).The saturation is attributed to the competition between the reduced effective mass and enhanced intravalley scattering induced by phonon softening once the detrimental intervalley scattering is effectively suppressed by sufficient valley separation.This study establishes a theoretical upper limit for the intrinsic electron transport of bilayer MoS2 masked by severe intervalley scattering.展开更多
As the frontier of multidimensional transportation systems,urban air mobility(UAM)is receiving increasing attention from international organizations,governments,and stakeholders in industry and academia owing to its h...As the frontier of multidimensional transportation systems,urban air mobility(UAM)is receiving increasing attention from international organizations,governments,and stakeholders in industry and academia owing to its high efficiency,low carbon footprint,and operational flexibility.Vertical take-off and landing(VTOL)infrastructure is the core facility that enables UAM and is therefore essential for its safe,efficient,and large-scale commercial implementation.However,the key technologies for establishing low-altitude VTOL infrastructure are still nascent,and government,industry,and academia have yet to harmonize the corresponding construction,management,and operation standards.To address this gap,we herein systematically review the related progress and trends,comprehensively surveying the key technologies of establishing VTOL infrastructure serving unmanned aerial vehicles(UAVs)and electric VTOL aircraft from three complementary perspectives of ground-side,airspace-side,and communication,navigation,surveillance,and information services.In the light of future UAM operations characterized by diverse vehicle types and dense air traffic,we propose a conceptual design for a public multioperator VTOL site to provide constructive insights into the sustainable growth of the low-altitude economy.展开更多
With the aim of understanding the relationships between organic small molecule field-effect transistors （FETs） and organic conjugated polymer FETs, we investigate the thickness dependence of surface morphology and c...With the aim of understanding the relationships between organic small molecule field-effect transistors （FETs） and organic conjugated polymer FETs, we investigate the thickness dependence of surface morphology and charge carrier mobility in pentacene and regioregular poly （3-hexylthiophene） （RR-P3HT） field-effect transistors. On the basis of the results of surface morphologies and electrical properties, we presume that the charge carrier mobility is largely related to the morphology of the organic active layer. We observe that the change trends of the surface morphologies （average size and average roughness） of pentacene and RR-P3HT thin films are mutually opposite, as the thickness of the organic layer increases. Further, we demonstrate that the change trends of the field-effect mobilities of pentacene and RR-P3HT FETs are also opposite to each other, as the thickness of the organic layer increases within its limit.展开更多
In order to enhance the performance of regioregular poly（3-hexylthiophene） （RR-P3HT） field-effect transistors （FETs）, RR-P3HT FETs are prepared by the spin-coating method followed by vacuum placement and anneali...In order to enhance the performance of regioregular poly（3-hexylthiophene） （RR-P3HT） field-effect transistors （FETs）, RR-P3HT FETs are prepared by the spin-coating method followed by vacuum placement and annealing. This paper reports that the crystal structure, the molecule interconnection, the surface morphology, and the charge carrier mobility of RR-P3HT films are affected by vacuum relaxation and annealing. The results reveal that the field-effect mobility of RR-P3HT FETs can reach 4.17×10^-2m^2/（V·s） by vacuum relaxation at room temperature due to an enhanced local self-organization. Furthermore, it reports that an appropriate annealing temperature can facilitate the crystal structure, the orientation and the interconnection of polymer molecules. These results show that the field-effect mobility of device annealed at 150 ℃ for 10 minutes in vacuum at atmosphere and followed by placement for 20 hours in vacuum at room temperature is enhanced dramatically to 9.00×10^-2m^2/（V·s）.展开更多
Poly(3-hexylthiophene)(P3HT)thin films,obtained by normal spin-coating and solvent vapor assisted spin-coating(SVASP)before and after thermal annealing(TA),and the corresponding devices were prepared to unravel the mi...Poly(3-hexylthiophene)(P3HT)thin films,obtained by normal spin-coating and solvent vapor assisted spin-coating(SVASP)before and after thermal annealing(TA),and the corresponding devices were prepared to unravel the microstructure-property relationship,which is of great importance for the development of organic electronics.When SVASP-TA films were used as the active layers of the organic field-effect transistors,a hole mobility up to 0.38 cm^(2)·V^(-1)·s^(-1)was achieved.This mobility was one of the highest values and one order of magnitude higher than that of the normal spin-coating films based transistors.The relationship between the microstructure and the device performance was fully investigated by UV-Vis absorption spectra,grazing incident X-ray diffraction(GIXD),and atomic force microscopy(AFM).The impressive mobility was attributed to the high crystallinity and ordered molecule packing,which stem from the synergistic effects of SVASP and thermal annealing.展开更多
This paper discusses the influence of Sb/In ratio on the transport properties and crystal quality of the 200 nm InAs_(x)Sb_(1-x)thin film.The Sb content of InAs_(x)Sb_(1-x)thin film in all samples was verified by HRXR...This paper discusses the influence of Sb/In ratio on the transport properties and crystal quality of the 200 nm InAs_(x)Sb_(1-x)thin film.The Sb content of InAs_(x)Sb_(1-x)thin film in all samples was verified by HRXRD of the symmetrical 004 reflections and asymmetrical 115 reflections.The calculation results show that the Sb component was 0.6 in the InAs_(x)Sb_(1-x)thin film grown under the conditions of Sb/In ratio of 6 and As/In ratio of 3,which has the highest electron mobility(28560 cm^(2)/V·s)at 300 K.At the same time,the influence ofⅤ/Ⅲratio on the transport properties and crystal quality of Al_(0.2)In_(0.8)Sb/InAs_(x)Sb_(1-x)quantum well heterostructures also has been investigated.As a result,the Al_(0.2)In_(0.8)Sb/InAs_(0.4)Sb_(0.6)quantum well heterostructure with a channel thickness of 30 nm grown under the conditions of Sb/In ratio of 6 and As/In ratio of 3 has a maximum electron mobility of 28300 cm^(2)/V·s and a minimum RMS roughness of 0.68 nm.Through optimizing the growth conditions,our samples have higher electron mobility and smoother surface morphology.展开更多
Various biaxial compressive strained GaSb p-channel metal-oxide-semiconductor field-effect transistors （MOSFETs） are experimentally and theoretically investigated, The biaxial compressive strained GaSb MOSFETs show ...Various biaxial compressive strained GaSb p-channel metal-oxide-semiconductor field-effect transistors （MOSFETs） are experimentally and theoretically investigated, The biaxial compressive strained GaSb MOSFETs show a high peak mobility of 638 cm2/V.s, which is 3.86 times of the extracted mobility of the fabricated GaSb MOSFETs without strain. Meanwhile, first principles calculations show that the hole effective mass of GaSb depends on the biaxial compressive strain. The biaxiai compressive strain brings a remarkable enhancement of the hole mobility caused by a significant reduction in the hole effective mass due to the modulation of the valence bands.展开更多
The tight sandstone reservoirs in the first sub-member of Chang 7 member(Chang 71)of Triassic Yanchang Formation in the Jiyuan area,Ordos Basin,show significant variations in microscopic pore-throat structure(PTS)and ...The tight sandstone reservoirs in the first sub-member of Chang 7 member(Chang 71)of Triassic Yanchang Formation in the Jiyuan area,Ordos Basin,show significant variations in microscopic pore-throat structure(PTS)and fluid mobility due to the influences of the northeast and northwest dual provenance systems.This study performed multiple experimental analyses on nine samples from the area to determine the petrological and petrophysical properties,as well as the PTS characteristics of reservoirs in different provenance-controlled regions.On this basis,the pore-throat size distribution(PSD)obtained from high-pressure mercury injection(HPMI)was utilized to convert the NMR movable fluid T2spectrum,allowing for quantitative characterization of the full PSD and the occurrence characteristics of movable fluids.A systematic analysis was conducted on the primary controlling factors affecting fluid mobility in the reservoir.The results indicated that the lithology in the eastern and western regions is lithic arkose.The eastern sandstones,being farther from the provenance,exhibit higher contents of feldspar and lithic fragments,along with the development of more dissolution pores.The reservoir possesses good petrophysical properties,low displacement pressure,and high pore-throat connectivity and homogeneity,indicating strong fluid mobility.In contrast,the western sandstones,being nearer to the provenance,exhibit poor grain sorting,high contents of lithic fragments,strong compaction and cementation effects,resulting in poor petrophysical properties,and strong pore-throat heterogeneity,revealing weak fluid mobility.The range of full PSD in the eastern reservoir is wider than that in the western reservoir,with relatively well-developed macropores.The macropores are the primary space for occurrence of movable fluids,and controls the fluid mobility of the reservoir.The effective porosity of movable fluids(EPMF)quantitatively represents the pore space occupied by movable fluids within the reservoir and correlates well with porosity,permeability,and PTS parameters,making it a valuable parameter for evaluating fluid mobility.Under the multi-provenance system,the eastern and western reservoirs underwent different sedimentation and diagenesis processes,resulting in differential distribution of reservoir mineral components and pore types,which in turn affects the PTS heterogeneity and reservoir quality.The composition and content of reservoir minerals are intrinsic factors influencing fluid mobility,while the microscopic PTS is the primary factor controlling it.Low clay mineral content,welldeveloped macropores,and weak pore-throat heterogeneity all contribute to the storage and seepage of reservoir fluids.展开更多
Based on the experimental results of casting thin section,low temperature nitrogen adsorption,high pressure mercury injection,nuclear magnetic resonance T2 spectrum,contact angle and oil-water interfacial tension,the ...Based on the experimental results of casting thin section,low temperature nitrogen adsorption,high pressure mercury injection,nuclear magnetic resonance T2 spectrum,contact angle and oil-water interfacial tension,the relationship between pore throat structure and crude oil mobility characteristics of full particle sequence reservoirs in the Lower Permian Fengcheng Formation of Mahu Sag,Junggar Basin,are revealed.(1)With the decrease of reservoir particle size,the volume of pores connected by large throats and the volume of large pores show a decreasing trend,and the distribution and peak ranges of throat and pore radius shift to smaller size in an orderly manner.The upper limits of throat radius,porosity and permeability of unconventional reservoirs in Fengcheng Formation are approximately 0.7μm,8%and 0.1×10^(−3)μm^(2),respectively.(2)As the reservoir particle size decreases,the distribution and peak ranges of pores hosting retained oil and movable oil are shifted to a smaller size in an orderly manner.With the increase of driving pressure,the amount of retained and movable oil of the larger particle reservoir samples shows a more obvious trend of decreasing and increasing,respectively.(3)With the increase of throat radius,the driving pressure of reservoir with different particle levels presents three stages,namely rapid decrease,slow decrease and stabilization.The oil driving pressures of various reservoirs and the differences of them decrease with the increase of temperature and obviously decrease with the increase of throat radius.According to the above experimental analysis,it is concluded that the deep shale oil of Fengcheng Formation in Mahu Sag has great potential for production under geological conditions.展开更多
C60 field-effect transistor （OFET） with a mobility as high as 5.17 cm2/V.s is fabricated. In our experiment, an ultrathin pentacene passivation layer on poly-（methyl methacrylate） （PMMA） insulator and a bathophe...C60 field-effect transistor （OFET） with a mobility as high as 5.17 cm2/V.s is fabricated. In our experiment, an ultrathin pentacene passivation layer on poly-（methyl methacrylate） （PMMA） insulator and a bathophenanthroline （Bphen）/Ag bilayer electrode are prepared. The OFET shows a significant enhancement of electron mobility compared with the corresponding device with a single PMMA insultor and an Ag electrode. By analysing the C60 film with atomic force microscopy and X-ray diffraction techniques, it is shown that the pentacene passivation layer can contribute to C60 film growth with the large grain size and significantly improve crystallinity. Moreover, the Bphen buffer layer can reduce the electron contact barrier from Ag electrodes to C60 film efficiently.展开更多
A novel characterization method is proposed to extract the optical frequency field-effect mobility(μ_(op,FE))of transparent conductive oxide(TCO)materials by a tunable silicon microring resonator with a heterogeneous...A novel characterization method is proposed to extract the optical frequency field-effect mobility(μ_(op,FE))of transparent conductive oxide(TCO)materials by a tunable silicon microring resonator with a heterogeneously integrated titanium-doped indium oxide(ITiO)/SiO_(2)/silicon metal–oxide–semiconductor(MOS)capacitor.By operating the microring in the accumulation mode,the quality factor and resonance wavelength shift are measured and subsequently used to derive the𝜇op,FE in the ultra-thin accumulation layer.Experimental results demonstrate that the μ_(op,FE) of ITiO increases from 25.3 to 38.4 cm2⋅V^(−1)⋅s^(−1) with increasing gate voltages,which shows a similar trend as that at the electric frequency.展开更多
Intercity mobility lays the foundation for capital flow,information flow,and knowledge flow,etc.,and is important for promoting regional integration.Although many scholars have studied intercity mobility in extensive ...Intercity mobility lays the foundation for capital flow,information flow,and knowledge flow,etc.,and is important for promoting regional integration.Although many scholars have studied intercity mobility in extensive well-developed urban agglomerations,few studies have examined the characteristics of intercity mobility at the county level and its impact on regionalization in western China.This study takes the Guanzhong Plain urban agglomeration(GPUA)as a case to study the geographical law of intercity mobility and then explore its impact on regionalization.The results obtained show that intercity mobility network exhibits a hub and spoke patterns focusing on major municipal districts at the county level.We also found a corridor effect that counties with higher travel volumes are mostly located along the trunk high speed railway(HSR)lines.Unlike previous studies,the distribution of intercity mobility is more concentrated than that of population and exhibits a super-linear behavior rule.There are the differences in gravity law for overall trips,weekday trips,weekend trips,and holiday trips.With the decrease of travel duration,the effect of attraction of destination is weakening,but the influence of distance decay is increasing.Finally,the spatial organization is still administrative-centric and is dominated by intraprefecture and intra-provincial development.Moreover,the coupled degree between network-based regionalization and attribute-based regionalization shows a decreasing trend from administrative via cultural to physical factors.These findings enrich the research on the intercity mobility and the regionalization in inland developing urban agglomerations.展开更多
Polymer field-effect transistors operated in the n-channel model with a top-gate/bottom-contact are processed using a solution method. The transistor performance depends on the gate dielectric layer. A high performanc...Polymer field-effect transistors operated in the n-channel model with a top-gate/bottom-contact are processed using a solution method. The transistor performance depends on the gate dielectric layer. A high performance polymer transistor is achieved, with the saturated electron mobility of about 0.46cm2/Vs, threshold voltage nearly 0 V and subthreshold sway of about 0.9 V/decade, employing a polystyrene （PS） dielectric layer. The transistor performances are further improved with increasing current and lower operation voltages by utilizing a bi-layer gate dielectric, comprising a thin PS dielectric layer adjacent to the semiconductor to minimize the density of the interface traps for obtaining a small VT, a large μ and a poly（methyl methacrylate） （PMMA） dielectric layer with a relatively high-k adjacent to the gate electrode for enlarging the capacitance, processed from the orthogonal solvents.展开更多
In this paper,the small-signal modeling of the Indium Phosphide High Electron Mobility Transistor(InP HEMT)based on the Transformer neural network model is investigated.The AC S-parameters of the HEMT device are train...In this paper,the small-signal modeling of the Indium Phosphide High Electron Mobility Transistor(InP HEMT)based on the Transformer neural network model is investigated.The AC S-parameters of the HEMT device are trained and validated using the Transformer model.In the proposed model,the eight-layer transformer encoders are connected in series and the encoder layer of each Transformer consists of the multi-head attention layer and the feed-forward neural network layer.The experimental results show that the measured and modeled S-parameters of the HEMT device match well in the frequency range of 0.5-40 GHz,with the errors versus frequency less than 1%.Compared with other models,good accuracy can be achieved to verify the effectiveness of the proposed model.展开更多
The fundamental I-V formula of an organic field effect transistor(OFET)is improved to overcome the divergence of the integrand,so it is very convenient for both numerical calculations and analytic derivations.The anal...The fundamental I-V formula of an organic field effect transistor(OFET)is improved to overcome the divergence of the integrand,so it is very convenient for both numerical calculations and analytic derivations.The analytic I-V formulae are derived based on the exponential mobility model and power-function mobility model,respectively,and the derived analytic formulae are applied to three OFET devices.The results calculated from the reformulated analytic I-V formulae taking in exponential and power function mobility models are all in good agreement with the experimental I-V data.The parameters μ_(0) and γ that are extracted from the mobility model and fitted by experimental data show simple Arrhenius temperature dependence and inverse linear relationship with temperature,respectively.These findings are very useful for practical applications and device simulations.展开更多
The 2025 Shanghai Auto Show reaffirmed its role as one of the world’s most influential automotive industry events,offering a panoramic view of the future shaped by intelligent and electrified vehicles.With over 200 n...The 2025 Shanghai Auto Show reaffirmed its role as one of the world’s most influential automotive industry events,offering a panoramic view of the future shaped by intelligent and electrified vehicles.With over 200 new models on display-85 percent of them new energy vehicles-this year’s show spotlighted how the global auto industry is pivoting rapidly towards an era of software-defined and AI-powered mobility.展开更多
Imagine a city that seems to hum rather than roar-a place where innovation moves at the pace of everyday life instead of like the flashy glamor of high-end tech hubs.This is Liuzhou,a city in southern China that is qu...Imagine a city that seems to hum rather than roar-a place where innovation moves at the pace of everyday life instead of like the flashy glamor of high-end tech hubs.This is Liuzhou,a city in southern China that is quietly shaping the future of electric vehicles(EVs).It has become an unlikely yet powerful engine of change in the world of clean mobility.展开更多
We simulate the current-voltage （I-V） characteristics of AlGaN/AlN/GaN heterostructure field-effect transistors （HFETs） with different gate lengths using the quasi-two-dimensional （quasi-2D） model. The calculati...We simulate the current-voltage （I-V） characteristics of AlGaN/AlN/GaN heterostructure field-effect transistors （HFETs） with different gate lengths using the quasi-two-dimensional （quasi-2D） model. The calculation results obtained using the modified mobility model are found to accord well with the experimental data. By analyzing the variation of the electron mobility for the two-dimensional electron gas （213EG） with the electric field in the linear region of the AlGaN/AlN/GaN HFET I-V output characteristics, it is found that the polarization Coulomb field scattering still plays an important role in the electron mobility of AlGaN/AlN/GaN HFETs at the higher drain voltage and channel electric field. As drain voltage and channel electric field increase, the 2DEG density reduces and the polarization Coulomb field scattering increases, as a result, the 2DEG electron mobility decreases.展开更多
基金funded by Major Project of the National Social Science Fund of China“Theory,Methods and Chinese Practices of National Welfare Accounting”[Grant No.22&ZD165]Key Project of the National Social Science Fund of China“Theoretical and Practical Research on the Compilation of Chinese Productivity Accounts”[Grant No.21AZD122].
文摘This study empirically examines how land finance in destination and origin cities affects willingness to engage in labor mobility and explores the underlying mechanisms.Using a two-way fixed effects model,we match macro data from 287 prefecture-level cities in China from 2000 to 2020 with data from the 2018 China Migrant Dynamic Survey(CMDS).The results are as follows:First,land finance in destination cities inhibits labor mobility willingness,while land finance in origin cities and labor mobility willingness have a U-shaped relationship,decreasing initially and then increasing.Second,local governments’dependence on land finance increases local housing prices and suppresses investment in non-economic public goods in the administrative area,thereby inhibiting labor mobility willingness;however,this also increases investment in economic public goods,attracting labor mobility willingness.Third,labor force age weakens the impact of land finance in origin cities on labor mobility willingness;however,age does not affect the impact of land finance in destination cities on labor mobility willingness.Fourth,land finance increases laborers’willingness to settle.
基金supported by Princess Nourah bint Abdulrahman University Researchers Supporting Project No.PNURSP2025R510Princess Nourah bint Abdulrahman University,Riyadh,Saudi Arabia.
文摘The technological advancement of the vehicular Internet ofThings(IoT)has revolutionized Intelligent Transportation Systems(ITS)into next-generation ITS.The connectivity of IoT nodes enables improved data availability and facilitates automatic control in the ITS environment.The exponential increase in IoT nodes has significantly increased the demand for an energy-efficient,mobility-aware,and secure system for distributed intelligence.This article presents a mobility-aware Deep Reinforcement Learning based Federated Learning(DRL-FL)approach to design an energy-efficient and threat-resilient ITS.In this approach,a Policy Proximal Optimization(PPO)-based DRL agent is first employed for adaptive client selection.Second,an autoencoder-based anomaly detectionmodule is considered for malicious node detection.Results reveal that the proposed framework achieved an 8%higher accuracy increase,and 15%lower energy consumption.Themodel also demonstrates greater resilience under adversarial conditions compared to the state of the art in federated learning.The adaptability of the proposed approach makes it a compelling choice for next-generation vehicular networks.
基金supported by the National Key R&D Program of China (Grant No.2022YFA1402503)the High Performance Computing Center of Jilin University,China。
文摘Bilayer MoS2 is a promising channel candidate for extending Moore’s law,owing to its optimal channel thickness and improved suppression of extrinsic scattering compared to monolayers.However,its intrinsic phonon-limited electron mobility is severely limited by enhanced K–Q intervalley scattering arising from the multivalley conduction band feature inherent to the bilayer structure.To overcome this bottleneck,we propose a“valley separation engineering”strategy that combines a twist angle near 30°with applied stress.Our first-principles calculations demonstrate that although valley separation can be continuously increased using this strategy,the electron mobility saturates at∼200 cm^(2)⋅V^(−1)⋅s^(−1).The saturation is attributed to the competition between the reduced effective mass and enhanced intravalley scattering induced by phonon softening once the detrimental intervalley scattering is effectively suppressed by sufficient valley separation.This study establishes a theoretical upper limit for the intrinsic electron transport of bilayer MoS2 masked by severe intervalley scattering.
基金supported by the National Natural Science Foundation of China(No.U2333214).
文摘As the frontier of multidimensional transportation systems,urban air mobility(UAM)is receiving increasing attention from international organizations,governments,and stakeholders in industry and academia owing to its high efficiency,low carbon footprint,and operational flexibility.Vertical take-off and landing(VTOL)infrastructure is the core facility that enables UAM and is therefore essential for its safe,efficient,and large-scale commercial implementation.However,the key technologies for establishing low-altitude VTOL infrastructure are still nascent,and government,industry,and academia have yet to harmonize the corresponding construction,management,and operation standards.To address this gap,we herein systematically review the related progress and trends,comprehensively surveying the key technologies of establishing VTOL infrastructure serving unmanned aerial vehicles(UAVs)and electric VTOL aircraft from three complementary perspectives of ground-side,airspace-side,and communication,navigation,surveillance,and information services.In the light of future UAM operations characterized by diverse vehicle types and dense air traffic,we propose a conceptual design for a public multioperator VTOL site to provide constructive insights into the sustainable growth of the low-altitude economy.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10774013 and 10804006)the National High Technology Research and Development Program of China (Grant No. 2006AA03Z412)+3 种基金the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20070004024)the Research Fund for the Youth Scholars of the Doctoral Program of Higher Education, China (Grant No. 20070004031)the New Star Plan of Science and Technology of Beijing, China(Grant No. 2007A024)the research grants from the Academy of Sciences for the Developing World (Grant No. B08002)
文摘With the aim of understanding the relationships between organic small molecule field-effect transistors （FETs） and organic conjugated polymer FETs, we investigate the thickness dependence of surface morphology and charge carrier mobility in pentacene and regioregular poly （3-hexylthiophene） （RR-P3HT） field-effect transistors. On the basis of the results of surface morphologies and electrical properties, we presume that the charge carrier mobility is largely related to the morphology of the organic active layer. We observe that the change trends of the surface morphologies （average size and average roughness） of pentacene and RR-P3HT thin films are mutually opposite, as the thickness of the organic layer increases. Further, we demonstrate that the change trends of the field-effect mobilities of pentacene and RR-P3HT FETs are also opposite to each other, as the thickness of the organic layer increases within its limit.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 10774013 and 10804006)the National High Technology Research and Development Program of China (Grant No 2006AA03Z0412)+4 种基金the Research Fund for the Doctoral Program of Higher Education of China (Grant No 20070004024)the Research Fund for the Youth Scholars of the Doctoral Program of Higher Education (Grant No 20070004031)the Beijing NOVA program (Grant No 2007A024)the the 111 of China (Grant No B08002)the research grants from the Academy of Sciences for the Developing World
文摘In order to enhance the performance of regioregular poly（3-hexylthiophene） （RR-P3HT） field-effect transistors （FETs）, RR-P3HT FETs are prepared by the spin-coating method followed by vacuum placement and annealing. This paper reports that the crystal structure, the molecule interconnection, the surface morphology, and the charge carrier mobility of RR-P3HT films are affected by vacuum relaxation and annealing. The results reveal that the field-effect mobility of RR-P3HT FETs can reach 4.17×10^-2m^2/（V·s） by vacuum relaxation at room temperature due to an enhanced local self-organization. Furthermore, it reports that an appropriate annealing temperature can facilitate the crystal structure, the orientation and the interconnection of polymer molecules. These results show that the field-effect mobility of device annealed at 150 ℃ for 10 minutes in vacuum at atmosphere and followed by placement for 20 hours in vacuum at room temperature is enhanced dramatically to 9.00×10^-2m^2/（V·s）.
基金the International Cooperation Fund of the Science and Technology Commission of Shanghai Municipality(No.20520741500)the Fundamental Research Funds for the Central Universities(No.2232020D-01)+2 种基金Shanghai Rising-Star Program(No.18QA1405000),the Innovation Program of Shanghai Municipal Education Commission(No.2017-01-07-00-03-E00055)the Science and Technology Commission of Shanghai Municipality(No.20JC1414900)the Open Research Fund of State Key Laboratory of Polymer Physics and Chemistry,Changchun Institute of Applied Chemistry,Chinese Academy of Sciences(No.2020-16).
文摘Poly(3-hexylthiophene)(P3HT)thin films,obtained by normal spin-coating and solvent vapor assisted spin-coating(SVASP)before and after thermal annealing(TA),and the corresponding devices were prepared to unravel the microstructure-property relationship,which is of great importance for the development of organic electronics.When SVASP-TA films were used as the active layers of the organic field-effect transistors,a hole mobility up to 0.38 cm^(2)·V^(-1)·s^(-1)was achieved.This mobility was one of the highest values and one order of magnitude higher than that of the normal spin-coating films based transistors.The relationship between the microstructure and the device performance was fully investigated by UV-Vis absorption spectra,grazing incident X-ray diffraction(GIXD),and atomic force microscopy(AFM).The impressive mobility was attributed to the high crystallinity and ordered molecule packing,which stem from the synergistic effects of SVASP and thermal annealing.
基金Supported by the Natural Science Basic Research Program of Shaanxi Province(2023-JC-QN-0758)Shaanxi University of Science and Technology Research Launch Project(2020BJ-26)Doctoral Research Initializing Fund of Hebei University of Science and Technology,China(1181476).
文摘This paper discusses the influence of Sb/In ratio on the transport properties and crystal quality of the 200 nm InAs_(x)Sb_(1-x)thin film.The Sb content of InAs_(x)Sb_(1-x)thin film in all samples was verified by HRXRD of the symmetrical 004 reflections and asymmetrical 115 reflections.The calculation results show that the Sb component was 0.6 in the InAs_(x)Sb_(1-x)thin film grown under the conditions of Sb/In ratio of 6 and As/In ratio of 3,which has the highest electron mobility(28560 cm^(2)/V·s)at 300 K.At the same time,the influence ofⅤ/Ⅲratio on the transport properties and crystal quality of Al_(0.2)In_(0.8)Sb/InAs_(x)Sb_(1-x)quantum well heterostructures also has been investigated.As a result,the Al_(0.2)In_(0.8)Sb/InAs_(0.4)Sb_(0.6)quantum well heterostructure with a channel thickness of 30 nm grown under the conditions of Sb/In ratio of 6 and As/In ratio of 3 has a maximum electron mobility of 28300 cm^(2)/V·s and a minimum RMS roughness of 0.68 nm.Through optimizing the growth conditions,our samples have higher electron mobility and smoother surface morphology.
基金Project supported by the National Basic Research Program of China(Grant No.2011CBA00602)the National Science and Technology Major Project of the Ministry of Science and Technology of China(Grant No.2011ZX02708-002)
文摘Various biaxial compressive strained GaSb p-channel metal-oxide-semiconductor field-effect transistors （MOSFETs） are experimentally and theoretically investigated, The biaxial compressive strained GaSb MOSFETs show a high peak mobility of 638 cm2/V.s, which is 3.86 times of the extracted mobility of the fabricated GaSb MOSFETs without strain. Meanwhile, first principles calculations show that the hole effective mass of GaSb depends on the biaxial compressive strain. The biaxiai compressive strain brings a remarkable enhancement of the hole mobility caused by a significant reduction in the hole effective mass due to the modulation of the valence bands.
文摘The tight sandstone reservoirs in the first sub-member of Chang 7 member(Chang 71)of Triassic Yanchang Formation in the Jiyuan area,Ordos Basin,show significant variations in microscopic pore-throat structure(PTS)and fluid mobility due to the influences of the northeast and northwest dual provenance systems.This study performed multiple experimental analyses on nine samples from the area to determine the petrological and petrophysical properties,as well as the PTS characteristics of reservoirs in different provenance-controlled regions.On this basis,the pore-throat size distribution(PSD)obtained from high-pressure mercury injection(HPMI)was utilized to convert the NMR movable fluid T2spectrum,allowing for quantitative characterization of the full PSD and the occurrence characteristics of movable fluids.A systematic analysis was conducted on the primary controlling factors affecting fluid mobility in the reservoir.The results indicated that the lithology in the eastern and western regions is lithic arkose.The eastern sandstones,being farther from the provenance,exhibit higher contents of feldspar and lithic fragments,along with the development of more dissolution pores.The reservoir possesses good petrophysical properties,low displacement pressure,and high pore-throat connectivity and homogeneity,indicating strong fluid mobility.In contrast,the western sandstones,being nearer to the provenance,exhibit poor grain sorting,high contents of lithic fragments,strong compaction and cementation effects,resulting in poor petrophysical properties,and strong pore-throat heterogeneity,revealing weak fluid mobility.The range of full PSD in the eastern reservoir is wider than that in the western reservoir,with relatively well-developed macropores.The macropores are the primary space for occurrence of movable fluids,and controls the fluid mobility of the reservoir.The effective porosity of movable fluids(EPMF)quantitatively represents the pore space occupied by movable fluids within the reservoir and correlates well with porosity,permeability,and PTS parameters,making it a valuable parameter for evaluating fluid mobility.Under the multi-provenance system,the eastern and western reservoirs underwent different sedimentation and diagenesis processes,resulting in differential distribution of reservoir mineral components and pore types,which in turn affects the PTS heterogeneity and reservoir quality.The composition and content of reservoir minerals are intrinsic factors influencing fluid mobility,while the microscopic PTS is the primary factor controlling it.Low clay mineral content,welldeveloped macropores,and weak pore-throat heterogeneity all contribute to the storage and seepage of reservoir fluids.
基金Supported by Leading Talent Program of Autonomous Region(2022TSYCLJ0070)PetroChina Prospective and Basic Technological Project(2021DJ0108)Natural Science Foundation for Outstanding Young People in Shandong Province(ZR2022YQ30).
文摘Based on the experimental results of casting thin section,low temperature nitrogen adsorption,high pressure mercury injection,nuclear magnetic resonance T2 spectrum,contact angle and oil-water interfacial tension,the relationship between pore throat structure and crude oil mobility characteristics of full particle sequence reservoirs in the Lower Permian Fengcheng Formation of Mahu Sag,Junggar Basin,are revealed.(1)With the decrease of reservoir particle size,the volume of pores connected by large throats and the volume of large pores show a decreasing trend,and the distribution and peak ranges of throat and pore radius shift to smaller size in an orderly manner.The upper limits of throat radius,porosity and permeability of unconventional reservoirs in Fengcheng Formation are approximately 0.7μm,8%and 0.1×10^(−3)μm^(2),respectively.(2)As the reservoir particle size decreases,the distribution and peak ranges of pores hosting retained oil and movable oil are shifted to a smaller size in an orderly manner.With the increase of driving pressure,the amount of retained and movable oil of the larger particle reservoir samples shows a more obvious trend of decreasing and increasing,respectively.(3)With the increase of throat radius,the driving pressure of reservoir with different particle levels presents three stages,namely rapid decrease,slow decrease and stabilization.The oil driving pressures of various reservoirs and the differences of them decrease with the increase of temperature and obviously decrease with the increase of throat radius.According to the above experimental analysis,it is concluded that the deep shale oil of Fengcheng Formation in Mahu Sag has great potential for production under geological conditions.
基金supported by the National Science Foundation for Post-Doctoral Scientists of China (Grant No.20100471667)the Natural Science Foundation of Chongqing Science and Technology Commission (CQ CSTC) (Grant No.2011jjA40020)+1 种基金the National Natural Science Foundation of China (Grant Nos.60736005 and 61021061)the Scientific Research Foundation for the Returned Overseas Chinese Scholars,Ministry of Education of China (Grant No.GGRYJJ08-05)
文摘C60 field-effect transistor （OFET） with a mobility as high as 5.17 cm2/V.s is fabricated. In our experiment, an ultrathin pentacene passivation layer on poly-（methyl methacrylate） （PMMA） insulator and a bathophenanthroline （Bphen）/Ag bilayer electrode are prepared. The OFET shows a significant enhancement of electron mobility compared with the corresponding device with a single PMMA insultor and an Ag electrode. By analysing the C60 film with atomic force microscopy and X-ray diffraction techniques, it is shown that the pentacene passivation layer can contribute to C60 film growth with the large grain size and significantly improve crystallinity. Moreover, the Bphen buffer layer can reduce the electron contact barrier from Ag electrodes to C60 film efficiently.
基金National Aeronautics and Space Administration(80NSSC21K0230)National Science Foundation Directorate for Engineering(1927271)Air Force Office of Scientific Research(FA9550-17-1-0071).
文摘A novel characterization method is proposed to extract the optical frequency field-effect mobility(μ_(op,FE))of transparent conductive oxide(TCO)materials by a tunable silicon microring resonator with a heterogeneously integrated titanium-doped indium oxide(ITiO)/SiO_(2)/silicon metal–oxide–semiconductor(MOS)capacitor.By operating the microring in the accumulation mode,the quality factor and resonance wavelength shift are measured and subsequently used to derive the𝜇op,FE in the ultra-thin accumulation layer.Experimental results demonstrate that the μ_(op,FE) of ITiO increases from 25.3 to 38.4 cm2⋅V^(−1)⋅s^(−1) with increasing gate voltages,which shows a similar trend as that at the electric frequency.
基金Under the auspices of National Natural Science Foundation of China(No.42371189)Central University Basic Research Fund of China(No.24ZYYB017)。
文摘Intercity mobility lays the foundation for capital flow,information flow,and knowledge flow,etc.,and is important for promoting regional integration.Although many scholars have studied intercity mobility in extensive well-developed urban agglomerations,few studies have examined the characteristics of intercity mobility at the county level and its impact on regionalization in western China.This study takes the Guanzhong Plain urban agglomeration(GPUA)as a case to study the geographical law of intercity mobility and then explore its impact on regionalization.The results obtained show that intercity mobility network exhibits a hub and spoke patterns focusing on major municipal districts at the county level.We also found a corridor effect that counties with higher travel volumes are mostly located along the trunk high speed railway(HSR)lines.Unlike previous studies,the distribution of intercity mobility is more concentrated than that of population and exhibits a super-linear behavior rule.There are the differences in gravity law for overall trips,weekday trips,weekend trips,and holiday trips.With the decrease of travel duration,the effect of attraction of destination is weakening,but the influence of distance decay is increasing.Finally,the spatial organization is still administrative-centric and is dominated by intraprefecture and intra-provincial development.Moreover,the coupled degree between network-based regionalization and attribute-based regionalization shows a decreasing trend from administrative via cultural to physical factors.These findings enrich the research on the intercity mobility and the regionalization in inland developing urban agglomerations.
基金Supported by the National Natural Science Foundation of China under Grant No 61177028
文摘Polymer field-effect transistors operated in the n-channel model with a top-gate/bottom-contact are processed using a solution method. The transistor performance depends on the gate dielectric layer. A high performance polymer transistor is achieved, with the saturated electron mobility of about 0.46cm2/Vs, threshold voltage nearly 0 V and subthreshold sway of about 0.9 V/decade, employing a polystyrene （PS） dielectric layer. The transistor performances are further improved with increasing current and lower operation voltages by utilizing a bi-layer gate dielectric, comprising a thin PS dielectric layer adjacent to the semiconductor to minimize the density of the interface traps for obtaining a small VT, a large μ and a poly（methyl methacrylate） （PMMA） dielectric layer with a relatively high-k adjacent to the gate electrode for enlarging the capacitance, processed from the orthogonal solvents.
基金Supported by the National Natural Science Foundation of China(62201293,62034003)the Open-Foundation of State Key Laboratory of Millimeter-Waves(K202313)the Jiangsu Province Youth Science and Technology Talent Support Project(JSTJ-2024-040)。
文摘In this paper,the small-signal modeling of the Indium Phosphide High Electron Mobility Transistor(InP HEMT)based on the Transformer neural network model is investigated.The AC S-parameters of the HEMT device are trained and validated using the Transformer model.In the proposed model,the eight-layer transformer encoders are connected in series and the encoder layer of each Transformer consists of the multi-head attention layer and the feed-forward neural network layer.The experimental results show that the measured and modeled S-parameters of the HEMT device match well in the frequency range of 0.5-40 GHz,with the errors versus frequency less than 1%.Compared with other models,good accuracy can be achieved to verify the effectiveness of the proposed model.
文摘The fundamental I-V formula of an organic field effect transistor(OFET)is improved to overcome the divergence of the integrand,so it is very convenient for both numerical calculations and analytic derivations.The analytic I-V formulae are derived based on the exponential mobility model and power-function mobility model,respectively,and the derived analytic formulae are applied to three OFET devices.The results calculated from the reformulated analytic I-V formulae taking in exponential and power function mobility models are all in good agreement with the experimental I-V data.The parameters μ_(0) and γ that are extracted from the mobility model and fitted by experimental data show simple Arrhenius temperature dependence and inverse linear relationship with temperature,respectively.These findings are very useful for practical applications and device simulations.
文摘The 2025 Shanghai Auto Show reaffirmed its role as one of the world’s most influential automotive industry events,offering a panoramic view of the future shaped by intelligent and electrified vehicles.With over 200 new models on display-85 percent of them new energy vehicles-this year’s show spotlighted how the global auto industry is pivoting rapidly towards an era of software-defined and AI-powered mobility.
文摘Imagine a city that seems to hum rather than roar-a place where innovation moves at the pace of everyday life instead of like the flashy glamor of high-end tech hubs.This is Liuzhou,a city in southern China that is quietly shaping the future of electric vehicles(EVs).It has become an unlikely yet powerful engine of change in the world of clean mobility.
基金supported by the National Natural Science Foundation of China (Grant No. 11174182)the Specialized Research Fund for the Doctoral Program of Higher Education,China (Grant No. 20110131110005)
文摘We simulate the current-voltage （I-V） characteristics of AlGaN/AlN/GaN heterostructure field-effect transistors （HFETs） with different gate lengths using the quasi-two-dimensional （quasi-2D） model. The calculation results obtained using the modified mobility model are found to accord well with the experimental data. By analyzing the variation of the electron mobility for the two-dimensional electron gas （213EG） with the electric field in the linear region of the AlGaN/AlN/GaN HFET I-V output characteristics, it is found that the polarization Coulomb field scattering still plays an important role in the electron mobility of AlGaN/AlN/GaN HFETs at the higher drain voltage and channel electric field. As drain voltage and channel electric field increase, the 2DEG density reduces and the polarization Coulomb field scattering increases, as a result, the 2DEG electron mobility decreases.
