Vehicle-to-vehicle(V2V)communication appeals to increasing research interest as a result of its applications to provide safety information as well as infotainment services.The increasing demand of transmit rates and v...Vehicle-to-vehicle(V2V)communication appeals to increasing research interest as a result of its applications to provide safety information as well as infotainment services.The increasing demand of transmit rates and various requirements of quality of services(QoS)in vehicular communication scenarios call for the integration of V2V communication systems and potential techniques in the future wireless communications,such as full duplex(FD)and non-orthogonal multiple access(NOMA)which enhance spectral efficiency and provide massive connectivity.However,the large amount of data transmission and user connectivity give rise to the concern of security issues and personal privacy.In order to analyze the security performance of V2V communications,we introduce a cooperative NOMA V2V system model with an FD relay.This paper focuses on the security performance of the FD-NOMA based V2V system on the physical layer perspective.We first derive several analytical results of the ergodic secrecy capacity.Then,we propose a secrecy sum rate optimization scheme utilizing the instantaneous channel state information(CSI),which is formulated as a non-convex optimization problem.Based on the differential structure of the non-convex constraints,the original problem is approximated and solved by a series of convex optimization problems.Simulation results validate the analytical results and the effectiveness of the secrecy sum rate optimization algorithm.展开更多
In this paper, we study relay selection under outdated channel state information（CSI） in a decode-and-forward（DF） cooperative system. Unlike previous researches on cooperative communication under outdated CSI, we ...In this paper, we study relay selection under outdated channel state information（CSI） in a decode-and-forward（DF） cooperative system. Unlike previous researches on cooperative communication under outdated CSI, we consider that the channel varies continuously over time, i.e., the channel not only changes between relay selection and data transmission but also changes during data transmission. Thus the level of accuracy of the CSI used in relay selection degrades with data transmission. We first evaluate the packet error rate（PER） of the cooperative system under continuous time-varying fading channel, and find that the PER performance deteriorates more seriously under continuous time-varying fading channel than when the channel is assumed to be constant during data transmission. Then, we propose a repeated relay selection（RRS） strategy to improve the PER performance, in which the forwarded data is divided into multiple segments and relay is reselected before the transmission of each segment based on the updated CSI. Finally, we propose a combined relay selection（CRS） strategy which takes advantage of three different relay selection strategies to further mitigate the impact of outdated CSI.展开更多
Permeable roads generally exhibit inferior mechanical properties and shorter service life than traditional dense-graded/impermeable roads.Furthermore,the incorporation of recycled aggregates in their construction may ...Permeable roads generally exhibit inferior mechanical properties and shorter service life than traditional dense-graded/impermeable roads.Furthermore,the incorporation of recycled aggregates in their construction may exacerbate these limitations.To address these issues,this study introduced a novel cement-stabilized permeable recycled aggregate material.A total of 162 beam specimens prepared with nine different levels of cement-aggregate ratio were tested to evaluate their permeability,bending load,and bending fatigue life.The experimental results indicate that increasing the content of recycled aggregates led to a reduction in both permeability and bending load.Additionally,the inclusion of recycled aggregates diminished the energy dissipation capacity of the specimens.These findings were used to establish a robust relationship between the initial damage in cement-stabilized permeable recycled aggregate material specimens and their fatigue life,and to propose a predictive model for their fatigue performance.Further,a method for assessing fatigue damage based on the evolution of fatigue-induced strain and energy dissipation was developed.The findings of this study provide valuable insights into the mechanical behavior and fatigue performance of cement-stabilized permeable recycled aggregate materials,offering guidance for the design of low-carbon-emission,permeable,and durable roadways incorporating recycled aggregates.展开更多
Purpose-With the rapid advancement of China’s high-speed rail network,the density of train operations is on the rise.To address the challenge of shortening train tracking intervals while enhancing transportation effi...Purpose-With the rapid advancement of China’s high-speed rail network,the density of train operations is on the rise.To address the challenge of shortening train tracking intervals while enhancing transportation efficiency,the multi-objective dynamic optimization of the train operation process has emerged as a critical issue.Design/methodology/approach-Train dynamic model is established by analyzing the force of the train in the process of tracing operation.The train tracing operation model is established according to the dynamic mechanical model of the train tracking process,and the dynamic optimization analysis is carried out with comfort,energy saving and punctuality as optimization objectives.To achieve multi-objective dynamic optimization,a novel train tracking operation calculation method is proposed,utilizing the improved grey wolf optimization algorithm(MOGWO).The proposed method is simulated and verified based on the train characteristics and line data of CR400AF electric multiple units.Findings-The simulation results prove that the optimized MOGWO algorithm can be computed quickly during train tracks,the optimum results can be given within 5s and the algorithm can converge effectively in different optimization target directions.The optimized speed profile of the MOGWO algorithm is smoother and more stable and meets the target requirements of energy saving,punctuality and comfort while maximally respecting the speed limit profile.Originality/value-The MOGWO train tracking interval optimization method enhances the tracking process while ensuring a safe tracking interval.This approach enables the trailing train to operate more comfortably,energy-efficiently and punctually,aligning with passenger needs and industry trends.The method offers valuable insights for optimizing the high-speed train tracking process.展开更多
With the integration of informatization and intelligence into the Communication-Based Train Control(CBTC)systems,the system is facing an increasing number of information security threats.As an important method of char...With the integration of informatization and intelligence into the Communication-Based Train Control(CBTC)systems,the system is facing an increasing number of information security threats.As an important method of characterizing the system security status,the security situation assessment is used to analyze the system security situation.However,existing situation assessment methods fail to integrate the coupling relationship between the physical layer and the information layer of the CBTC systems,and cannot dynamically characterize the real-time security situation changes under cyber attacks.In this paper,a hierarchical security situation assessment approach is proposed to address the security challenges of CBTC systems,which can perceive cyber attacks,quantify the security situation,and characterize the security situation changes under cyber attacks.Specifically,for the physical layer ofCBTC systems,the impact of cyber attacks is evaluated with the train punctuality rate and train departure interval indicators.For the information layer of CBTC systems,the system vulnerabilities and system threats are selected as static level indicators,and the critical network characteristics are selected as dynamic level indicators to quantify the real-time security situation.Finally,the comprehensive security situation assessment value of the CBTC systems is obtained by integrating the physical and information layer indicators.Simulation results illustrate that the proposed approach can dynamically characterize the real-time security situation of CBTC systems,enhancing the ability to perceive and assess information security risks.展开更多
Conventional nonlinear Raman–Nath diffraction(NRND)spots exhibit a straight-line distribution when the pump laser enters the nonlinear dielectric grating at normal incidence or at oblique incidence.Here,we report on ...Conventional nonlinear Raman–Nath diffraction(NRND)spots exhibit a straight-line distribution when the pump laser enters the nonlinear dielectric grating at normal incidence or at oblique incidence.Here,we report on the first observation of the conical NRND phenomenon from a submicron-thick periodically poled lithium niobate thin film(PPLNTF)sample under a near-infrared femtosecond pulse laser excitation at various cone angles.All the multi-order second harmonic generation(SHG)diffraction signals present a novel evolution arc-shaped arrangement feature.展开更多
Reliable detection of weak phase signals under significant channel loss and complex noise environments is a crucial step for practical applications of optical integrated communication and sensing systems. In this lett...Reliable detection of weak phase signals under significant channel loss and complex noise environments is a crucial step for practical applications of optical integrated communication and sensing systems. In this letter, we propose and experimentally demonstrate an enhanced long-distance weak signal transmission method assisted by weak measurement. Performing heterodyne detection and light intensity compensation on two nearly symmetric post-selected paths, the method enables real-time estimation of a time-varying phase while maintaining robustness against technical noises proportional to light intensity or photon number, detector common-mode noise, and significant attenuation over long-distance transmission. Experimental results indicate a potential phase sensitivity at the level of 10-8rad even with a signal light intensity attenuation of 48.1 d B. Potentially, combining the adaptive adjustment strategy, the method may provide a viable solution in remote weak signal detection and extraction,thereby contributing to optical integrated communication and sensing.展开更多
On September 5,2022,an M_(S)6.8 earthquake struck Luding County,Kardze Prefecture,Sichuan Province—an area that is particularly vulnerable to geological changes.The earthquake caused considerable damage along the hig...On September 5,2022,an M_(S)6.8 earthquake struck Luding County,Kardze Prefecture,Sichuan Province—an area that is particularly vulnerable to geological changes.The earthquake caused considerable damage along the highway,leading to road disruptions and blockages,further isolating earthquake-stricken areas.Accordingly,a rapid survey of the main highways in this area was conducted,and 507 damage points were identified.Roadbed damage accounted for more than 70%of the total damages.Co-seismic disasters were primarily distributed along the highways on both sides of the Dadu River in the reservoir area of the Dagangshan Hydropower Station,Caoke Township,and Detuo Township.Further,six factors under three categories of the spatial distribution of highway damage in the earthquake-stricken areas were analyzed.The rate of highway damage was positively correlated with the seismic intensity but negatively correlated with the fault and river distances.The earthquake intensity had the most significant impact:37.5%of road disruptions were found in areas with an intensity of IX;this percentage was 1.6 and 5.8 times greater than those found in areas with intensities of VIII and VII,respectively.The roads with the most significant damage were in regions with intensities above VIII,faults within 5 km,slopes within 30°–70°,rivers within 100 m,and the presence of granite.This indicated that these factors aggravated highway disruption,resulting in more than 90% of damaged highways in strongly shaken regions.Our findings may provide guidance for efficient highway recovery following earthquakes.展开更多
To accelerate the large-scale integration of renewable energy and support the strategic goals of“carbon peaking and carbon neutrality,”High Voltage Direct Current(HVDC)transmission technology has made significant br...To accelerate the large-scale integration of renewable energy and support the strategic goals of“carbon peaking and carbon neutrality,”High Voltage Direct Current(HVDC)transmission technology has made significant breakthroughs.Among the various approaches,a hybrid DC transmission system that combines a line-commutated converter(LCC)and a voltage source converter(VSC)retains the inherent fault self-clearing capability of the LCC topology while mitigating the risk of commutation failure when connected to a weak grid.In this paper,based on the harmonic generation mechanisms of hybrid DC transmission systems,an improved 3-pulse harmonic source model of the LCC and a dynamic phase-sequence harmonic analysis model of the VSC are developed.The integrated harmonic model demonstrates strong adaptability in accurately calculating DC-side harmonics under the influence of power imbalances and background harmonics.Based on this model,the fundamental characteristics of DC-side harmonics in hybrid DC transmission systems are analyzed.To mitigate harmonic effects,this paper proposes an LCLC-trap2 high-order filter structure with parallel RC damping circuits and a co-optimized design of filter parameters.Finally,a±500 kV hybrid DC transmission systemismodeled using theMATLAB/Simulink platform,and the harmonic filtering performances of the conventional LC filter,the Butterworth filter,and the proposed filter are simulated and compared.The results verify that the proposed filter offers superior performance in suppressing low-order harmonics under nonideal operating conditions.展开更多
In the context of the diversity of smart terminals,the unity of the root of trust becomes complicated,which not only affects the efficiency of trust propagation,but also poses a challenge to the security of the whole ...In the context of the diversity of smart terminals,the unity of the root of trust becomes complicated,which not only affects the efficiency of trust propagation,but also poses a challenge to the security of the whole system.In particular,the solidification of the root of trust in non-volatile memory(NVM)restricts the system’s dynamic updating capability,which is an obvious disadvantage in a rapidly changing security environment.To address this issue,this study proposes a novel approach to generate root security parameters using static random access memory(SRAM)physical unclonable functions(PUFs).SRAM PUFs,as a security primitive,show great potential in lightweight security solutions due to their inherent physical properties,low cost and scalability.However,the stability of SRAM PUFs in harsh environments is a key issue.These environmental conditions include extreme temperatures,high humidity,and strong electromagnetic radiation,all of which can affect the performance of SRAM PUFs.In order to ensure the stability of root safety parameters under these conditions,this study proposes an integrated approach that covers not only the acquisition of entropy sources,but also the implementation of algorithms and configuration management.In addition,this study develops a series of reliability-enhancing algorithms,including adaptive parameter selection,data preprocessing,auxiliary data generation,and error correction,which are essential for improving the performance of SRAM PUFs in harsh environments.Based on these techniques,this study establishes six types of secure parameter generation mechanisms,which not only improve the security of the system,but also enhance its adaptability in variable environments.Through a series of experiments,we verify the effectiveness of the proposed method.Under 10 different environmental conditions,our method is able to achieve full recovery of security data with an error rate of less than 25%,which proves the robustness and reliability of our method.These results not only provide strong evidence for the stability of SRAM PUFs in practical applications,but also provide a new direction for future research in the field of smart terminal security.展开更多
This investigation examines the shear performance of concrete T-beams reinforced with thin layers of ultra-high performance concrete(UHPC)through an approach that integrates experimental evaluation,numerical simulatio...This investigation examines the shear performance of concrete T-beams reinforced with thin layers of ultra-high performance concrete(UHPC)through an approach that integrates experimental evaluation,numerical simulation,and practical project verification.The research is based on a real bridge,and in accordance with the similarity principle,three reduced-scale T-beams with varying UHPC thicknesses were fabricated and tested to examine their failure modes and shear behaviors.A finite element model was created to enhance understanding of how UHPC reinforces these structures,while also considering the effects of material strength and arrangement.In addition to the laboratory tests,the actual bridge was analyzed to assess the effectiveness of the proposed strengthening technique.Results indicated that concrete T-beams strengthened with 30 mm-thick layers of UHPC had significant improvements,including a 491%increase in shear stiffness,a 23.15%rise in ultimate resistance,and a 155%enhancement in deformability compared to unreinforced T-beams.Furthermore,these improvements continued to increase with the application of thicker UHPC layers.Using 120MPa-grade UHPC with a thickness of 50mmand an A-type arrangement ensured that the dynamic and static performance of the T-beambridge met established code requirements.This research highlights the potential of UHPC thin layers in effectively reinforcing concrete beams for enhanced shear performance.展开更多
Wearable photodetectors have come under the limelight of optoelectronic technologies on account of multiple advantages spanning light weight,easy-portability,excellent bendability,outstanding conformability,etc.Among ...Wearable photodetectors have come under the limelight of optoelectronic technologies on account of multiple advantages spanning light weight,easy-portability,excellent bendability,outstanding conformability,etc.Among diverse candidate materials,low-dimensional van der Waals materials(LDvdWMs)have emerged to be preeminent owing to the dangling-bond-free surface,exceptional carrier mobility,nanoscale dimensionality,and excellent light-harvesting capability.However,to date,the majority of flexible LDvdWM photodetectors have been fabricated through exfoliation-,transfer-,or solution-processing methods,which are plagued by limitations such as low production yield,inadequate photosensitivity,and sluggish response rate.Thus far,constructing LDvdWM photodetectors in situ on flexible substrates remains quite challenging due to the irreconcilable contradiction between the weak robustness of flexible polymer substrates against high temperature and the large thermal budget required for crystallization.This study develops scalable preparation of Sb_(2)Se_(3)nanofilm directly on flexible polyimide substrates by exploiting pulsed-laser deposition(PLD),where highly energetic species can be generated to enable overcoming the reaction barrier for crystallization at a relatively low temperature.The corresponding Sb_(2)Se_(3)photodetectors have exhibited high responsivity of 1.15 A/W,exceptional external quantum efficiency of 269%,and impressive specific detectivity reaching 2.4×10^(11)Jones,coupled with swift switching characteristics.Importantly,excellent durability to repeated bending treatments has been confirmed by the consistent photoresponse over 500 convex/concave bending cycles.Furthermore,the device has showcased strong robustness against extrinsic impinging.In the end,by using Sb_(2)Se_(3)photodetectors as sensing components,wide-band imaging beyond human vision and heart rate monitoring have been realized.This study has underscored the high efficacy of PLD for reconciling the long-standing contradiction between the weak robustness of flexible polymer substrates against high temperature and the substantial thermal energy required for crystallization,opening new opportunities towards next-generation wearable optoelectronic industry.展开更多
Hexavalent chromium(Cr^(6+))poses significant risks to both individuals and the environment.However,direct detection of Cr^(6+)in fully aqueous media with high sensitivity and selectivity is extremely challenging.Here...Hexavalent chromium(Cr^(6+))poses significant risks to both individuals and the environment.However,direct detection of Cr^(6+)in fully aqueous media with high sensitivity and selectivity is extremely challenging.Herein,an isoindigo-derived chemosensor(II-MT)is developed and utilized as a single use paper-based sensor.This sensor allows for quick and simple screening of Cr^(6+)in water through a significant color change that is visible to the naked eyes.Moreover,via a simple UV detection method,the new sensor enables an accurate trace-level detection of Cr^(6+)at concentration as low as 0.1μM.This detection capability is one order of magnitude lower than the recommended limit for drinking water(0.960μM)set by World Health Organization(WHO).More importantly,the sensor delivers an average recovery of 104.5%and 98.25%for the detection of tap water samples.This convenient,yet accurate,quantification method for Cr^(6+)in spiked tap water was compared to the certified inductive coupled plasma(ICP)method.The agreement between the measurements obtained by our sensor and the ICP method was 93.57%.Mechanistic studies using Fourier Transform Infrared Spectroscopy(FT-IR)indicate a nucleophilic attack to the carbonyl group of II-MT by HCrO_(4)^(-),resulting in the dye color changing from brown to colorless.Overall,this novel chemosensor has a high potential for application as a selective,sensitive,and disposable paper sensor for direct and rapid screening of Cr^(6+)in real world environments.展开更多
In soft-lattice lead-halide perovskites,the polaronic effects involving stabilization of localized charge character by structural deformations and polarizations have an important effect on the properties of functional...In soft-lattice lead-halide perovskites,the polaronic effects involving stabilization of localized charge character by structural deformations and polarizations have an important effect on the properties of functional materials such as the band gap,which has attracted considerable investigations.However,the concept of polaron assisted nonlinear photonics remains largely unexplored,which has a wide range of applications from optoelectronics to telecommunications and quantum technologies.Here,we report the first observation of the polaronic state assisted saturable absorption through subbandgap excitation with a redshift exceeding 60 meV.By combining photoluminescence,transient absorption measurements and density functional theory calculations,we explicate that the anomalous nonlinear saturable absorption under sub-bandgap excitation is caused by the transient picosecond timescale polaronic state formed by strong carrier/excitonphonon coupling effect.The bandgap fluctuation caused by polaron formation can be further tuned through excitonphonon coupling of perovskites with different Young’s modulus.This suggests that we can design targeted soft lattice lead-halide perovskite with a specific structure to effectively manipulate exciton-phonon coupling and exciton-polaron formation.These findings profoundly expand our understanding of exciton-polaronic nonlinear optics physics and provide an ideal platform for developing actively tunable nonlinear photonics applications.展开更多
Optical clocks with thermal atoms are characterized by compact size,simple structure,reduced weight,and low power consumption and have the potential for broad out-of-the-lab and commercial applications.Here,we demonst...Optical clocks with thermal atoms are characterized by compact size,simple structure,reduced weight,and low power consumption and have the potential for broad out-of-the-lab and commercial applications.Here,we demonstrate a 459 nm optical clock based on the 6S_(1/2)-7P_(1/2)transition in thermal^(133)Cs atoms.Two methods,modulation transfer spectroscopy(MTS)and frequency modulation spectroscopy(FMS),are employed to stabilize the frequency of a 459 nm commercial laser to the atomic transition.The MTS-MTS and MTS-FMS beat-note measurements show short-term frequency stabilities of 3.7×10^(-13)/√t and 6.4×10^(-13)/√t,respectively,at the averaging time t.The 459 nm passive optical clock further serves as the pump for an active 1470 nm optical clock based on the cavityless lasing.The resultant 1470 nm output power reaches over 10μW and the pump-beam-induced light shift is estimated to be 2π×11 Hz with a fractional uncertainty of 2.4×10^(-18).These results demonstrate the feasibility of hybridizing passive and active optical clocks,providing a promising route toward compact multi-wavelength optical frequency standards.展开更多
The phenomenon that a clock at a higher gravitational potential ticks faster than one at a lower potential,also known as gravitational redshift,is one of the classical tests of Einstein’s theory of general relativity...The phenomenon that a clock at a higher gravitational potential ticks faster than one at a lower potential,also known as gravitational redshift,is one of the classical tests of Einstein’s theory of general relativity.Owing to their ultra-high accuracy and stability,state-of-the-art optical lattice clocks have enabled resolving the gravitational redshift with a millimeter-scale height difference.Further reducing the vertical inter-clock separation down to the sub-millimeter level and especially shortening the required measurement time may be achieved by employing spin squeezing.Here,we theoretically investigate the spin-squeezing-enhanced differential frequency comparison between two optical clocks within a lattice-trapped cloud of^(171)Yb atoms.The numerical results illustrate that for a sample of 10^(4)atoms,the atomic-collision-limited resolution of the vertical separation between two clocks can reach 0.48 mm,corresponding to a fractional gravitational redshift at the 10^(-20)level.In addition,the required averaging time may be reduced to less than one hundredth of that of conventional clocks with independent atoms.Our work opens a door to the future spin-squeezing-enhanced test of general relativity.展开更多
In this paper,a novel train positioning method considering satellite raw observation data was proposed,which aims to promote train positioning performance from an innovative perspective of the train satellite-based po...In this paper,a novel train positioning method considering satellite raw observation data was proposed,which aims to promote train positioning performance from an innovative perspective of the train satellite-based positioning error sources.The method focused on overcoming the abnormal observations in satellite observation data caused by railway environment rather than the positioning results.Specifically,the relative positioning experimental platform was built and the zero-baseline method was firstly employed to evaluate the carrier phase data quality,and then,GNSS combined observation models were adopted to construct the detection values,which were applied to judge abnormal-data through the dual-frequency observations.Further,ambiguity fixing optimization was investigated based on observation data selection in partly-blocked environments.The results show that the proposed method can effectively detect and address abnormal observations and improve positioning stability.Cycle slips and gross errors can be detected and identified based on dual-frequency global navigation satellite system data.After adopting the data selection strategy,the ambiguity fixing percentage was improved by 29.2%,and the standard deviation in the East,North,and Up components was enhanced by 12.7%,7.4%,and 12.5%,respectively.The proposed method can provide references for train positioning performance optimization in railway environments from the perspective of positioning error sources.展开更多
Pulsed-laser deposition has been developed to prepare large-area In_(2)S_(3)nanofilms and their photoelectric characteristics have been investigated.The In_(2)S_(3)nanofilm grown under 500℃is highly oriented along th...Pulsed-laser deposition has been developed to prepare large-area In_(2)S_(3)nanofilms and their photoelectric characteristics have been investigated.The In_(2)S_(3)nanofilm grown under 500℃is highly oriented along the(103)direction with exceptional crystallinity.The corresponding(103)-oriented In_(2)S_(3)photodetectors exhibit broadband photoresponse from 370.6 nm to 1064 nm.Under 635 nm illumination,the optimized responsivity,external quantum efficiency,and detectivity reach 19.8 A/W,3869%,and 2.59×10^(12)Jones,respectively.In addition,the device exhibits short rise/decay time of 3.9/3.0 ms.Of note,first-principles calculations have unveiled that the effective carrier mass along the(103)lattice plane is much smaller than those along the(100),(110)and(111)lattice planes,which thereby enables high-efficiency transport of photocarriers and thereby the excellent photosensitivity.Profited from the sizable bandgap,the In_(2)S_(3)photodetectors also showcase strong robustness against elevated operating temperature.In the end,proof-of-concept imaging application beyond human vision and under high operating temperature as well as heart rate monitoring have been achieved by using the In_(2)S_(3)device of the sensing component.This study introduces a novel crystal orientation engineering paradigm for the implementation of next-generation advanced optoelectronic systems.展开更多
We successfully prepared a series of rare-earth doped borosilicate glasses using the melt-quenching method,and carefully investigated the luminescent properties and the spectral modulation of Tb/Eucodoped borosilicate...We successfully prepared a series of rare-earth doped borosilicate glasses using the melt-quenching method,and carefully investigated the luminescent properties and the spectral modulation of Tb/Eucodoped borosilicate glasses under UV(200-400 nm)excitation.The results show that the prepared samples have the characteristics of broadband response,excellent transparency and tunable luminescence.By adjusting the excitation wavelength,the emissions of Tb^(3+),Eu^(2+)and Eu^(3+)ions are observed,which exhibit yellow-green,blue,red color and multi-color even white emissions,respectively.Moreover,the energy transfer between Tb^(3+)and Eu^(3+)ions in the codoped glasses is confirmed.Tb^(3+)absorbs a large number of solar-blind light,transfers to Eu^(3+)and results in intense visible emission in a wide waveband range.This makes the Tb/Eu co-doped glass a desirable candidate for solar-blind light detections.The photodetection system was built and shows a strong and stable response to the UV light of 210-400 nm.Due to broad detection range,high sensitivity and stability,our results offer strong implications for the development of photodetection device for diverse applications.展开更多
In view of the high complexity of the objective world, an economic dependence between subsystems(paired and unpaired) is proposed, and then the maintenance cost and time under different economic dependences are formul...In view of the high complexity of the objective world, an economic dependence between subsystems(paired and unpaired) is proposed, and then the maintenance cost and time under different economic dependences are formulated in a simple and consistent manner. Selective maintenance problem under economic dependence(EDSMP) is presented based on a series–parallel system in this paper. A case study shows that the system reliability is promoted to a certain extent, which can validate the validity of the EDSMP model. The influence of the ratio of set-up cost on system performance is mainly discussed under different economic dependences. Several existing improvements of classical exhaust algorithm are further modified to solve a large sized EDSMP rapidly. Experimental results illustrate that these improvements can reduce CPU time significantly.Furthermore the contribution of each improvement is defined here, and then their contributions are compared thoroughly.展开更多
基金supported in part by the National Key R&D Program of China under Grant 2018YFB2202202in part by Fundamental Research Funds for the Central Universities under Grants 21620351.
文摘Vehicle-to-vehicle(V2V)communication appeals to increasing research interest as a result of its applications to provide safety information as well as infotainment services.The increasing demand of transmit rates and various requirements of quality of services(QoS)in vehicular communication scenarios call for the integration of V2V communication systems and potential techniques in the future wireless communications,such as full duplex(FD)and non-orthogonal multiple access(NOMA)which enhance spectral efficiency and provide massive connectivity.However,the large amount of data transmission and user connectivity give rise to the concern of security issues and personal privacy.In order to analyze the security performance of V2V communications,we introduce a cooperative NOMA V2V system model with an FD relay.This paper focuses on the security performance of the FD-NOMA based V2V system on the physical layer perspective.We first derive several analytical results of the ergodic secrecy capacity.Then,we propose a secrecy sum rate optimization scheme utilizing the instantaneous channel state information(CSI),which is formulated as a non-convex optimization problem.Based on the differential structure of the non-convex constraints,the original problem is approximated and solved by a series of convex optimization problems.Simulation results validate the analytical results and the effectiveness of the secrecy sum rate optimization algorithm.
文摘In this paper, we study relay selection under outdated channel state information（CSI） in a decode-and-forward（DF） cooperative system. Unlike previous researches on cooperative communication under outdated CSI, we consider that the channel varies continuously over time, i.e., the channel not only changes between relay selection and data transmission but also changes during data transmission. Thus the level of accuracy of the CSI used in relay selection degrades with data transmission. We first evaluate the packet error rate（PER） of the cooperative system under continuous time-varying fading channel, and find that the PER performance deteriorates more seriously under continuous time-varying fading channel than when the channel is assumed to be constant during data transmission. Then, we propose a repeated relay selection（RRS） strategy to improve the PER performance, in which the forwarded data is divided into multiple segments and relay is reselected before the transmission of each segment based on the updated CSI. Finally, we propose a combined relay selection（CRS） strategy which takes advantage of three different relay selection strategies to further mitigate the impact of outdated CSI.
基金Project(2024JJ2073)supported by the Science Fund for Distinguished Young Scholars of Hunan Province,ChinaProjects(2023YFC3807205,2019YFC1904704)+4 种基金supported by the National Key R&D Program of ChinaProject(52178443)supported by the National Natural Science Foundation of ChinaProject(2024ZZTS0109)supported by Fundamental Research Funds for the Central Universities of Central South University,China。
文摘Permeable roads generally exhibit inferior mechanical properties and shorter service life than traditional dense-graded/impermeable roads.Furthermore,the incorporation of recycled aggregates in their construction may exacerbate these limitations.To address these issues,this study introduced a novel cement-stabilized permeable recycled aggregate material.A total of 162 beam specimens prepared with nine different levels of cement-aggregate ratio were tested to evaluate their permeability,bending load,and bending fatigue life.The experimental results indicate that increasing the content of recycled aggregates led to a reduction in both permeability and bending load.Additionally,the inclusion of recycled aggregates diminished the energy dissipation capacity of the specimens.These findings were used to establish a robust relationship between the initial damage in cement-stabilized permeable recycled aggregate material specimens and their fatigue life,and to propose a predictive model for their fatigue performance.Further,a method for assessing fatigue damage based on the evolution of fatigue-induced strain and energy dissipation was developed.The findings of this study provide valuable insights into the mechanical behavior and fatigue performance of cement-stabilized permeable recycled aggregate materials,offering guidance for the design of low-carbon-emission,permeable,and durable roadways incorporating recycled aggregates.
基金funded by the China Academy of Railway Sciences Corporation Limited Scientific Research Project(No:2023YJ080).
文摘Purpose-With the rapid advancement of China’s high-speed rail network,the density of train operations is on the rise.To address the challenge of shortening train tracking intervals while enhancing transportation efficiency,the multi-objective dynamic optimization of the train operation process has emerged as a critical issue.Design/methodology/approach-Train dynamic model is established by analyzing the force of the train in the process of tracing operation.The train tracing operation model is established according to the dynamic mechanical model of the train tracking process,and the dynamic optimization analysis is carried out with comfort,energy saving and punctuality as optimization objectives.To achieve multi-objective dynamic optimization,a novel train tracking operation calculation method is proposed,utilizing the improved grey wolf optimization algorithm(MOGWO).The proposed method is simulated and verified based on the train characteristics and line data of CR400AF electric multiple units.Findings-The simulation results prove that the optimized MOGWO algorithm can be computed quickly during train tracks,the optimum results can be given within 5s and the algorithm can converge effectively in different optimization target directions.The optimized speed profile of the MOGWO algorithm is smoother and more stable and meets the target requirements of energy saving,punctuality and comfort while maximally respecting the speed limit profile.Originality/value-The MOGWO train tracking interval optimization method enhances the tracking process while ensuring a safe tracking interval.This approach enables the trailing train to operate more comfortably,energy-efficiently and punctually,aligning with passenger needs and industry trends.The method offers valuable insights for optimizing the high-speed train tracking process.
基金supported in part by the project of the State Key Laboratory of Advanced Rail Autonomous Operation(RAO2023ZZ004)in part by the Beijing Natural Science Foundation-Fengtai Rail Transit Frontier Research Joint Fund(L211002)+2 种基金in part by the Foundation of China State Railway Group Corporation Limited under Grant L2021G003in part by the Scientific and Technical Research Fund of China Academy of Railway Sciences Corporation Limited under Grant 2021YJ094in part by the Project I23L00200 and Project I24F00010.
文摘With the integration of informatization and intelligence into the Communication-Based Train Control(CBTC)systems,the system is facing an increasing number of information security threats.As an important method of characterizing the system security status,the security situation assessment is used to analyze the system security situation.However,existing situation assessment methods fail to integrate the coupling relationship between the physical layer and the information layer of the CBTC systems,and cannot dynamically characterize the real-time security situation changes under cyber attacks.In this paper,a hierarchical security situation assessment approach is proposed to address the security challenges of CBTC systems,which can perceive cyber attacks,quantify the security situation,and characterize the security situation changes under cyber attacks.Specifically,for the physical layer ofCBTC systems,the impact of cyber attacks is evaluated with the train punctuality rate and train departure interval indicators.For the information layer of CBTC systems,the system vulnerabilities and system threats are selected as static level indicators,and the critical network characteristics are selected as dynamic level indicators to quantify the real-time security situation.Finally,the comprehensive security situation assessment value of the CBTC systems is obtained by integrating the physical and information layer indicators.Simulation results illustrate that the proposed approach can dynamically characterize the real-time security situation of CBTC systems,enhancing the ability to perceive and assess information security risks.
基金Science and Technology Project of Guangdong(2020B010190001)National Natural Science Foundation of China(12434016,11974119)+1 种基金Guangzhou Science and Technology Plan Project(2023A04J1309)National Funded Postdoctoral Researcher Program(GZB20240785)。
文摘Conventional nonlinear Raman–Nath diffraction(NRND)spots exhibit a straight-line distribution when the pump laser enters the nonlinear dielectric grating at normal incidence or at oblique incidence.Here,we report on the first observation of the conical NRND phenomenon from a submicron-thick periodically poled lithium niobate thin film(PPLNTF)sample under a near-infrared femtosecond pulse laser excitation at various cone angles.All the multi-order second harmonic generation(SHG)diffraction signals present a novel evolution arc-shaped arrangement feature.
基金supported by the National Natural Science Foundation of China(Grant No.62471289)the Natural Science Foundation of Shanghai (Grant No.24ZR1432900)+1 种基金the Innovation Program for Quantum Science and Technology (Grant No.2021ZD0300703)Shanghai Municipal Science and Technology Major Project (Grant No.2019SHZDZX01)。
文摘Reliable detection of weak phase signals under significant channel loss and complex noise environments is a crucial step for practical applications of optical integrated communication and sensing systems. In this letter, we propose and experimentally demonstrate an enhanced long-distance weak signal transmission method assisted by weak measurement. Performing heterodyne detection and light intensity compensation on two nearly symmetric post-selected paths, the method enables real-time estimation of a time-varying phase while maintaining robustness against technical noises proportional to light intensity or photon number, detector common-mode noise, and significant attenuation over long-distance transmission. Experimental results indicate a potential phase sensitivity at the level of 10-8rad even with a signal light intensity attenuation of 48.1 d B. Potentially, combining the adaptive adjustment strategy, the method may provide a viable solution in remote weak signal detection and extraction,thereby contributing to optical integrated communication and sensing.
基金funded by Sichuan Science and Technology Program(Nos.2023NSFSC1414 and 2023NSFSC0263)Sichuan Transportation Science and Technology Program(No.2018-B-05)Sichuan Communication Surveying&Design Institute CO.,LTD(No.232023002).
文摘On September 5,2022,an M_(S)6.8 earthquake struck Luding County,Kardze Prefecture,Sichuan Province—an area that is particularly vulnerable to geological changes.The earthquake caused considerable damage along the highway,leading to road disruptions and blockages,further isolating earthquake-stricken areas.Accordingly,a rapid survey of the main highways in this area was conducted,and 507 damage points were identified.Roadbed damage accounted for more than 70%of the total damages.Co-seismic disasters were primarily distributed along the highways on both sides of the Dadu River in the reservoir area of the Dagangshan Hydropower Station,Caoke Township,and Detuo Township.Further,six factors under three categories of the spatial distribution of highway damage in the earthquake-stricken areas were analyzed.The rate of highway damage was positively correlated with the seismic intensity but negatively correlated with the fault and river distances.The earthquake intensity had the most significant impact:37.5%of road disruptions were found in areas with an intensity of IX;this percentage was 1.6 and 5.8 times greater than those found in areas with intensities of VIII and VII,respectively.The roads with the most significant damage were in regions with intensities above VIII,faults within 5 km,slopes within 30°–70°,rivers within 100 m,and the presence of granite.This indicated that these factors aggravated highway disruption,resulting in more than 90% of damaged highways in strongly shaken regions.Our findings may provide guidance for efficient highway recovery following earthquakes.
基金funded by the Natural Science Foundation of Chongqing(CSTB2023NSCQMSX0279)the Science and Technology Research Program of Chongqing Municipal Education Commission(KJQN202201119).
文摘To accelerate the large-scale integration of renewable energy and support the strategic goals of“carbon peaking and carbon neutrality,”High Voltage Direct Current(HVDC)transmission technology has made significant breakthroughs.Among the various approaches,a hybrid DC transmission system that combines a line-commutated converter(LCC)and a voltage source converter(VSC)retains the inherent fault self-clearing capability of the LCC topology while mitigating the risk of commutation failure when connected to a weak grid.In this paper,based on the harmonic generation mechanisms of hybrid DC transmission systems,an improved 3-pulse harmonic source model of the LCC and a dynamic phase-sequence harmonic analysis model of the VSC are developed.The integrated harmonic model demonstrates strong adaptability in accurately calculating DC-side harmonics under the influence of power imbalances and background harmonics.Based on this model,the fundamental characteristics of DC-side harmonics in hybrid DC transmission systems are analyzed.To mitigate harmonic effects,this paper proposes an LCLC-trap2 high-order filter structure with parallel RC damping circuits and a co-optimized design of filter parameters.Finally,a±500 kV hybrid DC transmission systemismodeled using theMATLAB/Simulink platform,and the harmonic filtering performances of the conventional LC filter,the Butterworth filter,and the proposed filter are simulated and compared.The results verify that the proposed filter offers superior performance in suppressing low-order harmonics under nonideal operating conditions.
基金supported by National key Research and Development Program“Security Protection Technology for Critical Information Infrastructure of Distribution Network”(2022YFB3105100).
文摘In the context of the diversity of smart terminals,the unity of the root of trust becomes complicated,which not only affects the efficiency of trust propagation,but also poses a challenge to the security of the whole system.In particular,the solidification of the root of trust in non-volatile memory(NVM)restricts the system’s dynamic updating capability,which is an obvious disadvantage in a rapidly changing security environment.To address this issue,this study proposes a novel approach to generate root security parameters using static random access memory(SRAM)physical unclonable functions(PUFs).SRAM PUFs,as a security primitive,show great potential in lightweight security solutions due to their inherent physical properties,low cost and scalability.However,the stability of SRAM PUFs in harsh environments is a key issue.These environmental conditions include extreme temperatures,high humidity,and strong electromagnetic radiation,all of which can affect the performance of SRAM PUFs.In order to ensure the stability of root safety parameters under these conditions,this study proposes an integrated approach that covers not only the acquisition of entropy sources,but also the implementation of algorithms and configuration management.In addition,this study develops a series of reliability-enhancing algorithms,including adaptive parameter selection,data preprocessing,auxiliary data generation,and error correction,which are essential for improving the performance of SRAM PUFs in harsh environments.Based on these techniques,this study establishes six types of secure parameter generation mechanisms,which not only improve the security of the system,but also enhance its adaptability in variable environments.Through a series of experiments,we verify the effectiveness of the proposed method.Under 10 different environmental conditions,our method is able to achieve full recovery of security data with an error rate of less than 25%,which proves the robustness and reliability of our method.These results not only provide strong evidence for the stability of SRAM PUFs in practical applications,but also provide a new direction for future research in the field of smart terminal security.
基金The Science and Technology Project of Guangzhou(Grant#2024A04J9888)the National Natural Science Foundation of China(Grant#52278161)the Guangdong Basic and Applied Basic Research Foundation(Grant#2023A1515010535).
文摘This investigation examines the shear performance of concrete T-beams reinforced with thin layers of ultra-high performance concrete(UHPC)through an approach that integrates experimental evaluation,numerical simulation,and practical project verification.The research is based on a real bridge,and in accordance with the similarity principle,three reduced-scale T-beams with varying UHPC thicknesses were fabricated and tested to examine their failure modes and shear behaviors.A finite element model was created to enhance understanding of how UHPC reinforces these structures,while also considering the effects of material strength and arrangement.In addition to the laboratory tests,the actual bridge was analyzed to assess the effectiveness of the proposed strengthening technique.Results indicated that concrete T-beams strengthened with 30 mm-thick layers of UHPC had significant improvements,including a 491%increase in shear stiffness,a 23.15%rise in ultimate resistance,and a 155%enhancement in deformability compared to unreinforced T-beams.Furthermore,these improvements continued to increase with the application of thicker UHPC layers.Using 120MPa-grade UHPC with a thickness of 50mmand an A-type arrangement ensured that the dynamic and static performance of the T-beambridge met established code requirements.This research highlights the potential of UHPC thin layers in effectively reinforcing concrete beams for enhanced shear performance.
基金financially supported by National Natural Science Foundation of China(Nos.U2001215,52272175,12104517)Natural Science Foundation of Guangdong Province(Nos.2022A1515011487,2021A1515110403)+1 种基金Young Top Talents Program(No.2021QN02C068)State Key Laboratory of Optoelectronic Materials and Technologies(Sun Yat-sen University).
文摘Wearable photodetectors have come under the limelight of optoelectronic technologies on account of multiple advantages spanning light weight,easy-portability,excellent bendability,outstanding conformability,etc.Among diverse candidate materials,low-dimensional van der Waals materials(LDvdWMs)have emerged to be preeminent owing to the dangling-bond-free surface,exceptional carrier mobility,nanoscale dimensionality,and excellent light-harvesting capability.However,to date,the majority of flexible LDvdWM photodetectors have been fabricated through exfoliation-,transfer-,or solution-processing methods,which are plagued by limitations such as low production yield,inadequate photosensitivity,and sluggish response rate.Thus far,constructing LDvdWM photodetectors in situ on flexible substrates remains quite challenging due to the irreconcilable contradiction between the weak robustness of flexible polymer substrates against high temperature and the large thermal budget required for crystallization.This study develops scalable preparation of Sb_(2)Se_(3)nanofilm directly on flexible polyimide substrates by exploiting pulsed-laser deposition(PLD),where highly energetic species can be generated to enable overcoming the reaction barrier for crystallization at a relatively low temperature.The corresponding Sb_(2)Se_(3)photodetectors have exhibited high responsivity of 1.15 A/W,exceptional external quantum efficiency of 269%,and impressive specific detectivity reaching 2.4×10^(11)Jones,coupled with swift switching characteristics.Importantly,excellent durability to repeated bending treatments has been confirmed by the consistent photoresponse over 500 convex/concave bending cycles.Furthermore,the device has showcased strong robustness against extrinsic impinging.In the end,by using Sb_(2)Se_(3)photodetectors as sensing components,wide-band imaging beyond human vision and heart rate monitoring have been realized.This study has underscored the high efficacy of PLD for reconciling the long-standing contradiction between the weak robustness of flexible polymer substrates against high temperature and the substantial thermal energy required for crystallization,opening new opportunities towards next-generation wearable optoelectronic industry.
基金Saudi Arabian government,particularly Ministry of education,and Umm Al-Qura University for the financial support and the PhD scholarshipthe Australian Research Council(ARC)for the Future Fellowship(Grant No.FT130101337)。
文摘Hexavalent chromium(Cr^(6+))poses significant risks to both individuals and the environment.However,direct detection of Cr^(6+)in fully aqueous media with high sensitivity and selectivity is extremely challenging.Herein,an isoindigo-derived chemosensor(II-MT)is developed and utilized as a single use paper-based sensor.This sensor allows for quick and simple screening of Cr^(6+)in water through a significant color change that is visible to the naked eyes.Moreover,via a simple UV detection method,the new sensor enables an accurate trace-level detection of Cr^(6+)at concentration as low as 0.1μM.This detection capability is one order of magnitude lower than the recommended limit for drinking water(0.960μM)set by World Health Organization(WHO).More importantly,the sensor delivers an average recovery of 104.5%and 98.25%for the detection of tap water samples.This convenient,yet accurate,quantification method for Cr^(6+)in spiked tap water was compared to the certified inductive coupled plasma(ICP)method.The agreement between the measurements obtained by our sensor and the ICP method was 93.57%.Mechanistic studies using Fourier Transform Infrared Spectroscopy(FT-IR)indicate a nucleophilic attack to the carbonyl group of II-MT by HCrO_(4)^(-),resulting in the dye color changing from brown to colorless.Overall,this novel chemosensor has a high potential for application as a selective,sensitive,and disposable paper sensor for direct and rapid screening of Cr^(6+)in real world environments.
基金supported by the National Natural Science Foundation of China(Grant Nos.62275275,11904239,62422506,12474383,52273202)National Key R&D Program of China(2022YFA1604200)+2 种基金Natural Science Foundation of Hunan Province(Grant Nos.2021JJ40709,2022JJ20080,2024JJ6481)Postgraduate Innovative Project of Central South University(Grant No.CX20230246)supported in part by the High-Performance Computing Center of Central South University and Open Sharing Found for the Large-scale Instruments and Equipment of Central South University.
文摘In soft-lattice lead-halide perovskites,the polaronic effects involving stabilization of localized charge character by structural deformations and polarizations have an important effect on the properties of functional materials such as the band gap,which has attracted considerable investigations.However,the concept of polaron assisted nonlinear photonics remains largely unexplored,which has a wide range of applications from optoelectronics to telecommunications and quantum technologies.Here,we report the first observation of the polaronic state assisted saturable absorption through subbandgap excitation with a redshift exceeding 60 meV.By combining photoluminescence,transient absorption measurements and density functional theory calculations,we explicate that the anomalous nonlinear saturable absorption under sub-bandgap excitation is caused by the transient picosecond timescale polaronic state formed by strong carrier/excitonphonon coupling effect.The bandgap fluctuation caused by polaron formation can be further tuned through excitonphonon coupling of perovskites with different Young’s modulus.This suggests that we can design targeted soft lattice lead-halide perovskite with a specific structure to effectively manipulate exciton-phonon coupling and exciton-polaron formation.These findings profoundly expand our understanding of exciton-polaronic nonlinear optics physics and provide an ideal platform for developing actively tunable nonlinear photonics applications.
基金provided by CAS Project for Young Scientists in Basic Research(Grant No.YSBR-085)National Time Service Center(Grant No.E239SC1101)+1 种基金the funding of Wenzhou Major Science&Technology Innovation Key Project(Grant No.ZG2023021)supported by Innovation Program for Quantum Science and Technology(Grant No.2021ZD0303200).
文摘Optical clocks with thermal atoms are characterized by compact size,simple structure,reduced weight,and low power consumption and have the potential for broad out-of-the-lab and commercial applications.Here,we demonstrate a 459 nm optical clock based on the 6S_(1/2)-7P_(1/2)transition in thermal^(133)Cs atoms.Two methods,modulation transfer spectroscopy(MTS)and frequency modulation spectroscopy(FMS),are employed to stabilize the frequency of a 459 nm commercial laser to the atomic transition.The MTS-MTS and MTS-FMS beat-note measurements show short-term frequency stabilities of 3.7×10^(-13)/√t and 6.4×10^(-13)/√t,respectively,at the averaging time t.The 459 nm passive optical clock further serves as the pump for an active 1470 nm optical clock based on the cavityless lasing.The resultant 1470 nm output power reaches over 10μW and the pump-beam-induced light shift is estimated to be 2π×11 Hz with a fractional uncertainty of 2.4×10^(-18).These results demonstrate the feasibility of hybridizing passive and active optical clocks,providing a promising route toward compact multi-wavelength optical frequency standards.
基金supported by CAS Project for Young Scientists in Basic Research(Grant No.YSBR-085)the National Time Service Center(Grant No.E239SC1101)+1 种基金Innovation Program for Quantum Science and Technology(Grant No.2021ZD0303200)China Postdoctoral Science Foundation(Grant No.BX2021020).
文摘The phenomenon that a clock at a higher gravitational potential ticks faster than one at a lower potential,also known as gravitational redshift,is one of the classical tests of Einstein’s theory of general relativity.Owing to their ultra-high accuracy and stability,state-of-the-art optical lattice clocks have enabled resolving the gravitational redshift with a millimeter-scale height difference.Further reducing the vertical inter-clock separation down to the sub-millimeter level and especially shortening the required measurement time may be achieved by employing spin squeezing.Here,we theoretically investigate the spin-squeezing-enhanced differential frequency comparison between two optical clocks within a lattice-trapped cloud of^(171)Yb atoms.The numerical results illustrate that for a sample of 10^(4)atoms,the atomic-collision-limited resolution of the vertical separation between two clocks can reach 0.48 mm,corresponding to a fractional gravitational redshift at the 10^(-20)level.In addition,the required averaging time may be reduced to less than one hundredth of that of conventional clocks with independent atoms.Our work opens a door to the future spin-squeezing-enhanced test of general relativity.
基金Project(52272339)supported by the National Natural Science Foundation of ChinaProject(2023YFB390730303)supported by the National Key Research and Development Program of China+2 种基金Project(L2023G004)supported by the Science and Technology Research and Development Program of China State Railway Group Co.,Ltd.Project(QZKFKT2023-005)supported by the State Key Laboratory of Heavy-duty and Express High-power Electric Locomotive,ChinaProject(2022JZZ05)supported by the Open Foundation of MOE Key Laboratory of Engineering Structures of Heavy Haul Railway(Central South University),China。
文摘In this paper,a novel train positioning method considering satellite raw observation data was proposed,which aims to promote train positioning performance from an innovative perspective of the train satellite-based positioning error sources.The method focused on overcoming the abnormal observations in satellite observation data caused by railway environment rather than the positioning results.Specifically,the relative positioning experimental platform was built and the zero-baseline method was firstly employed to evaluate the carrier phase data quality,and then,GNSS combined observation models were adopted to construct the detection values,which were applied to judge abnormal-data through the dual-frequency observations.Further,ambiguity fixing optimization was investigated based on observation data selection in partly-blocked environments.The results show that the proposed method can effectively detect and address abnormal observations and improve positioning stability.Cycle slips and gross errors can be detected and identified based on dual-frequency global navigation satellite system data.After adopting the data selection strategy,the ambiguity fixing percentage was improved by 29.2%,and the standard deviation in the East,North,and Up components was enhanced by 12.7%,7.4%,and 12.5%,respectively.The proposed method can provide references for train positioning performance optimization in railway environments from the perspective of positioning error sources.
基金supported by the National Natural Science Foundation of China(Nos.52272175,U2001215 and 12474226)the Guangzhou Science and Technology Programme(No.2025A04J2596)+2 种基金the Natural Science Foundation of Guangdong Province(Nos.2024A1515012688,2022A1515011487,2021A1515110403 and 2023A1515010652)the Young Top Talents Program(No.2021QN02C068)State Key Laboratory of Optoelectronic Materials and Technologies of Sun Yat-sen University.
文摘Pulsed-laser deposition has been developed to prepare large-area In_(2)S_(3)nanofilms and their photoelectric characteristics have been investigated.The In_(2)S_(3)nanofilm grown under 500℃is highly oriented along the(103)direction with exceptional crystallinity.The corresponding(103)-oriented In_(2)S_(3)photodetectors exhibit broadband photoresponse from 370.6 nm to 1064 nm.Under 635 nm illumination,the optimized responsivity,external quantum efficiency,and detectivity reach 19.8 A/W,3869%,and 2.59×10^(12)Jones,respectively.In addition,the device exhibits short rise/decay time of 3.9/3.0 ms.Of note,first-principles calculations have unveiled that the effective carrier mass along the(103)lattice plane is much smaller than those along the(100),(110)and(111)lattice planes,which thereby enables high-efficiency transport of photocarriers and thereby the excellent photosensitivity.Profited from the sizable bandgap,the In_(2)S_(3)photodetectors also showcase strong robustness against elevated operating temperature.In the end,proof-of-concept imaging application beyond human vision and under high operating temperature as well as heart rate monitoring have been achieved by using the In_(2)S_(3)device of the sensing component.This study introduces a novel crystal orientation engineering paradigm for the implementation of next-generation advanced optoelectronic systems.
基金Project supported by the Significant Science and Technology Projects of LongMen Laboratory in Henan Province(231100220100,231100221100)the Key Research and Development Program of Henan province(231111222200)+2 种基金the College Students Innovations Special Project(202410482008)the National Natural Science Foundation of China(62275105,12104163)Basic Scientific Research Operating Expenses of Henan Academy of Sciences(240607004)。
文摘We successfully prepared a series of rare-earth doped borosilicate glasses using the melt-quenching method,and carefully investigated the luminescent properties and the spectral modulation of Tb/Eucodoped borosilicate glasses under UV(200-400 nm)excitation.The results show that the prepared samples have the characteristics of broadband response,excellent transparency and tunable luminescence.By adjusting the excitation wavelength,the emissions of Tb^(3+),Eu^(2+)and Eu^(3+)ions are observed,which exhibit yellow-green,blue,red color and multi-color even white emissions,respectively.Moreover,the energy transfer between Tb^(3+)and Eu^(3+)ions in the codoped glasses is confirmed.Tb^(3+)absorbs a large number of solar-blind light,transfers to Eu^(3+)and results in intense visible emission in a wide waveband range.This makes the Tb/Eu co-doped glass a desirable candidate for solar-blind light detections.The photodetection system was built and shows a strong and stable response to the UV light of 210-400 nm.Due to broad detection range,high sensitivity and stability,our results offer strong implications for the development of photodetection device for diverse applications.
基金supported by the National Science Foundation of China (Grant No. 61305083)
文摘In view of the high complexity of the objective world, an economic dependence between subsystems(paired and unpaired) is proposed, and then the maintenance cost and time under different economic dependences are formulated in a simple and consistent manner. Selective maintenance problem under economic dependence(EDSMP) is presented based on a series–parallel system in this paper. A case study shows that the system reliability is promoted to a certain extent, which can validate the validity of the EDSMP model. The influence of the ratio of set-up cost on system performance is mainly discussed under different economic dependences. Several existing improvements of classical exhaust algorithm are further modified to solve a large sized EDSMP rapidly. Experimental results illustrate that these improvements can reduce CPU time significantly.Furthermore the contribution of each improvement is defined here, and then their contributions are compared thoroughly.
