The floating population has become the main driver of urban population excessive growth in China＇s mega cities. Urban transit system （UTS） is a significant factor in population spatial distributions within urban ar...The floating population has become the main driver of urban population excessive growth in China＇s mega cities. Urban transit system （UTS） is a significant factor in population spatial distributions within urban areas, especially rapid and high-capacity transit systems. This paper analyzes the causal effects of the extension of expressways and subways between 2000 and 2010 in the Beijing Metropolitan Area （BMA）, focusing on the group differences between the local residents and the floating population. Due to the endogeneity of transportation improvements and population growth, Instrumental Variable （IV） regression model is applied to avoid this problem. The results show the local residents increased in the inner suburbs but decreased in the city center, while the floating population increased in the majority areas. IV regression results show that the extension of urban transit systems had statistically significant impacts on population growth across the BMA, The results also show that the extension of urban subway system had more effects on the floating population than the local residents across the BMA. It is mainly caused by the rather low fare of urban subway system. This implies that the excessive subsidy on urban subway system could result in ex- cessive floating population growth and residential differentiation, even residential segregation Hence, it is necessary to plan and design reasonable and scientific urban transit systems in order to advance reasonable population size and promote residential integration. Moreover, the regional analysis shows that the effects of urban transportation improvements on the local residents are not statistically significant in the inner suburbs. It implies that urban transportation improvements had limited effects on inducing people to move to suburban areas and controlling center city＇s population in Beijing. Therefore, it should be stressed the differenti- ated effects of urban transportation improvements on population distribution in the process of urban planning and population control.展开更多
The novel method to analyze metallic structure corrosion status was proposed in the presence of stray current in DC mass transit systems. Firstly, the characteristic parameter and the influence parameters for the corr...The novel method to analyze metallic structure corrosion status was proposed in the presence of stray current in DC mass transit systems. Firstly, the characteristic parameter and the influence parameters for the corrosion status were determined. Secondly, an experimental system was established for simulating the corrosion process within the stray current interference. Then, a predictive model for the corrosion status was built, using a support vector machine(SVM) method and experimental data. The data were divided into two sets, including training set and testing set. The training set was used to generate the SVM model and the testing set was used to evaluate the predictive performance of the SVM model. The results show that the relationship between the characteristic parameter and the influence parameters is nonlinear and the SVM model is suitable for predicting the corrosion status.展开更多
Nowadays,Rail Transit System has become one of the most important transportation means for the residents in Beijing.Construction of good urban rail transit landscape has also attracted increasing attentions from desig...Nowadays,Rail Transit System has become one of the most important transportation means for the residents in Beijing.Construction of good urban rail transit landscape has also attracted increasing attentions from designers and residents.The paper tries to explain that by taking sustainable landscape technological means and including plant utilization into all components of Beijing rail transit system the surrounding environment and inner environment of the subways could be expected to be improved.展开更多
The energy storage system charges the energy generated during braking and discharges it again when a vehicle accelerates on urban transit system. The energy storage system is considered to be one of the useful devices...The energy storage system charges the energy generated during braking and discharges it again when a vehicle accelerates on urban transit system. The energy storage system is considered to be one of the useful devices for energy storing and recycling. The energy storage system was developed and installed on the test track of Gyeongsan LRT in Korea. This paper presents the test plan and how much energy is saved by the energy storage system through the field test. When the energy storage system is on/off, the energy saving rate is obtained.展开更多
Accurate origin–destination(OD)demand prediction is crucial for the efficient operation and management of urban rail transit(URT)systems,particularly during a pandemic.However,this task faces several limitations,incl...Accurate origin–destination(OD)demand prediction is crucial for the efficient operation and management of urban rail transit(URT)systems,particularly during a pandemic.However,this task faces several limitations,including real-time availability,sparsity,and high-dimensionality issues,and the impact of the pandemic.Consequently,this study proposes a unified framework called the physics-guided adaptive graph spatial–temporal attention network(PAG-STAN)for metro OD demand prediction under pandemic conditions.Specifically,PAG-STAN introduces a real-time OD estimation module to estimate real-time complete OD demand matrices.Subsequently,a novel dynamic OD demand matrix compression module is proposed to generate dense real-time OD demand matrices.Thereafter,PAG-STAN leverages various heterogeneous data to learn the evolutionary trend of future OD ridership during the pandemic.Finally,a masked physics-guided loss function(MPG-loss function)incorporates the physical quantity information between the OD demand and inbound flow into the loss function to enhance model interpretability.PAG-STAN demonstrated favorable performance on two real-world metro OD demand datasets under the pandemic and conventional scenarios,highlighting its robustness and sensitivity for metro OD demand prediction.A series of ablation studies were conducted to verify the indispensability of each module in PAG-STAN.展开更多
Traditionally, the process used by public transportation entities to determine the acquisition strategy for new vehicle asset is based upon a broad range of criteria. Vehicle cost has been cited as one of the more cri...Traditionally, the process used by public transportation entities to determine the acquisition strategy for new vehicle asset is based upon a broad range of criteria. Vehicle cost has been cited as one of the more critical factors which decision makers consider. It is currently a common practice to consider other factors (life-cycle cost, fuel efficiency, vehicle reliability, environmental effects, etc.) that contribute to a more comprehensive approach. This study investigates the next generation of advancements in decision making tools in the area of the application of methods to quantify and manage uncertainty. In particular, the uncertainty comes from the public policy arena where future policy and regulations are not always based upon logical and predictable processes. The fleet decision making process in most governmental agencies is a very complex and interdependent activity. There are always competing forces and agendas within the view of the decision maker. Rarely is the decision maker a single person although, within the transit environment, there is often one person charged with the responsibility of fleet management. The focus of this research examines the decision making of the general transit agency community via the development of an expert systems prototype tool. A computer-based prototype system is developed which provide an expert knowledge-based recommendation, based upon variable user inputs. The results shown in this study show that a decision making tool for the management of transit system alternate fuel vehicle assets can be modeled and tested. The direct users of this research are the transit agency administrations. The results can be used by the management teams as a reliable input to inform their urban transit buses expansion decision making process.展开更多
Bus rapid transit (BRT) systems have been implemented in many cities over the past two decades. Widespread adoption of General Transit Feed Specification (GTFS), the deployment of high-fidelity bus GPS data tracking, ...Bus rapid transit (BRT) systems have been implemented in many cities over the past two decades. Widespread adoption of General Transit Feed Specification (GTFS), the deployment of high-fidelity bus GPS data tracking, and anonymized high-fidelity connected vehicle data from private vehicles have provided new opportunities for performance measures that can be used by both transit agencies and traffic signal system operators. This paper describes the use of trajectory-based data to develop performance measures for a BRT system in Indianapolis, Indiana. Over 3 million data records during the 3-month period between March and May 2022 are analyzed to develop visualizations and performance metrics. A methodology to estimate the average delay and schedule adherence is presented along a route comprised of 74 signals and 28 bus stations. Additionally, this research demonstrates how these performance measures can be used to evaluate dedicated and non-dedicated bus lanes with general traffic. Travel times and reliability of buses are compared with nearly 30 million private vehicle trips. Results show that median travel time for buses on dedicated bi-directional lanes is within one minute of general traffic and during peak periods the buses are often faster. Schedule adherence was observed to be more challenging, with approximately 3% of buses arriving within 1 minute on average during the 5AM hour and 5% of buses arriving 6 - 9 minutes late during the 5PM hour. The framework and performance measures presented in this research provide agencies and transportation professionals with tools to identify opportunities for adjustments and to justify investment decisions.展开更多
In this research three new innovative concepts are introduced and developed: the first defined as Transit System Maturity Components (TSMC), the second referred to as Transit System Maturity Scale (TSMS) and the third...In this research three new innovative concepts are introduced and developed: the first defined as Transit System Maturity Components (TSMC), the second referred to as Transit System Maturity Scale (TSMS) and the third labeled as Transit System Maturity Index (TSMI). The TSMC is meant to conceptualise the main strategic generic components characterising the maturity of transit systems. The TSMS is an S shaped scaling system for measuring maturity of transit system components. The TSMI presents an innovative index meant to assess the overall level of maturity of a city transit system. Such framework is envisaged to be used to determine and compare the overall maturity levels of transit systems in cities of the world as well as to act as a basis to identify strengths & gaps that need to be addressed/completed. Furthermore, it can also act as an ingredient in shaping and developing future road maps for transit system in cities across the world. The research concludes by demonstrating the applicability of TSMC, TSMS, and TSMI in conducting an initial assessment of the Transit System Maturity for the fast growing city of Dubai.展开更多
A new transportation technology known as personal rapid transit （PRT） is being developed by multiple different companies around the world, and one system is under commercial operations in the United Kingdom. Each de...A new transportation technology known as personal rapid transit （PRT） is being developed by multiple different companies around the world, and one system is under commercial operations in the United Kingdom. Each design is different, but they all share a need to operate many automated transit vehicles at very close headways. Safe operation will require a level of control an order of magnitude above any current transit system. As a result, new techniques will be needed for the development and testing of the mechanical and control systems. In this paper an apparatus for developing and testing a PRT vehicle control scheme is demonstrated. This system is composed of independent modules that represent virtual vehicles, a central control system, a man-machine interface and a monitoring device. It can be used to implement and to evaluate the designed vehicle control algorithm. The vehicle control algorithm is designed and simulated in a combined simulation platform that consists of Matlab/Simulink and Labview Simulation Interface Toolkit. Simple operational scenarios are proposed for the testing of the proposed vehicle control apparatus.展开更多
The phase transition among different solid forms of active pharmaceutical ingredients can significantly influence their physicochemical properties,potentially leading to clinical safety risks.However,phase transition ...The phase transition among different solid forms of active pharmaceutical ingredients can significantly influence their physicochemical properties,potentially leading to clinical safety risks.However,phase transition mechanisms remain under explored,especially in multi-component drugs.Here we report a novel ciprofloxacin-diclofenac salt system and investigate phase transitions among its anhydrate,dihydrate,and methanol solvate forms.The study focused on the influence of water activity and solvent vapor conditions,elucidating the role of vip molecules in driving these transitions.These findings offer new insights into polymorphic phase transitions,advancing our understanding of stability and performance in pharmaceutical formulations.展开更多
A dietary transition from refined to whole grains would optimize grain processing,reduce food loss and emissions,and increase food nutritional contents.The results of systematical analysis and calculations in our stud...A dietary transition from refined to whole grains would optimize grain processing,reduce food loss and emissions,and increase food nutritional contents.The results of systematical analysis and calculations in our study show that the average processing loss rate of grains including rice,wheat,and maize is approximately 4.1%in China due to the refinement,equivalent to an annual loss of around 13.3 Mt of grains.Furthermore,the refining process significantly reduces the nutritional contents of rice(51.6%),wheat flour(55.4%),and corn products(80.4%)mainly resulting from the removal of dietary fiber,minerals,and vitamins in refined grains.Replacing refined grains with whole grains in diets would lower agricultural carbon emissions by 2.7%,reducing agricultural water use by 4.3%,and saving arable land by 1,972,607 ha.Total environmental footprint could be reduced by 35%to 79%under three proposed scenarios.These findings indicate that shifting toward whole grain-based diets by Chinese consumers could reduce food losses,enhance human health,and improve environmental sustainability.This approach offers a promising strategy for transitioning towards more resilient and sustainable agri-food systems,benefiting human and planetary health.展开更多
Terahertz(THz)radiation possesses unique properties that make it a promising light source for applications in various fields,particularly spectroscopy and imaging.Ongoing research and development in THz technology has...Terahertz(THz)radiation possesses unique properties that make it a promising light source for applications in various fields,particularly spectroscopy and imaging.Ongoing research and development in THz technology has focused on developing or improving THz sources,detectors,and applications.At the PBP-CMU Electron Linac Laboratory(PCELL)of the Plasma and Beam Physics Research Facility in Chiang Mai University,high-intensity THz radiation has been generated in the form of coherent transition radiation(TR)and investigated since 2006 for electron beams with energies ranging from 8 to 12 MeV.In this study,we investigate and optimize the coherent TR arising from short electron bunches with energies ranging from 8 to 22 MeV using an upgraded linear-accelerator system with a higher radio-frequency(RF)power system.This radiation is then transported from the accelerator hall to the experimental room,in which the spectrometers are located.Electron-beam simulations are conducted to achieve short bunch lengths and small transverse beam sizes at the TR station.Radiation properties,including the radiation spectrum,angular distribution,and radiation polarization,are thoroughly investigated.The electron-bunch length is evaluated using the measuring system.The radiation-transport line is designed to achieve optimal frequency response and high transmission efficiency.A radiation-transmission efficiency of approximately 80-90%can be achieved with this designed system,along with a pulse energy ranging from 0.17 to 0.25μJ.The expected radiation spectral range covers up to 2 THz with a peak power of 0.5-1.25 MW.This coherent,broadband,and intense THz radiation will serve as a light source for THz spectroscopy and THz time-domain spectroscopy applications at the PCELL in the near future.展开更多
Within the transition process of urban rail transit systems,the challenges of high energy consumption,increasing carbon emissions,limited economic viability,and intricate risks emerge as significant hurdles.This paper...Within the transition process of urban rail transit systems,the challenges of high energy consumption,increasing carbon emissions,limited economic viability,and intricate risks emerge as significant hurdles.This paper proposes a novel energy utilization framework for the urban rail transit system that incorporates underground energy storage systems characterized by high resilience and low carbon.First,existing methods employed in urban rail transit are comprehensively reviewed.Then,a novel framework and strategic significance of the urban rail transit system incorporating underground energy storage systems are introduced.This integration effectively utilizes and manages diverse renewable energy sources and the available space resources.The viability is demonstrated through a case study by combining Nanjing metro.Finally,suggestions for research in pivotal areas are summarized.展开更多
We investigate dynamical quantum phase transitions(DQPTs)in Marko-vian open quantum systems using a variational quantum simulation(VQS)algorithm based on quantum state diffusion(QSD).This approach reformulates the Lin...We investigate dynamical quantum phase transitions(DQPTs)in Marko-vian open quantum systems using a variational quantum simulation(VQS)algorithm based on quantum state diffusion(QSD).This approach reformulates the Lindblad master equation as an ensemble of pure-state trajectories,enabling efficient simula-tion of dissipative quantum dynam-ics with effectively reduced quantum resources.Focusing on the one-di-mensional transverse-field Ising mod-el(TFIM),we simulate quench dynamics under both local and global Lindblad dissipation.The QSD-VQS algorithm accurately captures the nonanalytic cusps in the Loschmidt rate function,and reveals their modulation by dissipation strength and system size.Notably,DQPTs are gradually suppressed under strong local dissipation,while they persist under strong global dissipation due to collective environmental effects.Benchmarking against exact Lindblad solutions confirms the high accuracy and scalability of our method.展开更多
We consider a Bose-Einstein condensate loaded inside an optical cavity and exposed to two crossed coherent pump fields with same imbalance parameter γ.We identify different effects between pure standing wave fields(...We consider a Bose-Einstein condensate loaded inside an optical cavity and exposed to two crossed coherent pump fields with same imbalance parameter γ.We identify different effects between pure standing wave fields(γ=1)and the pump beams combining standing wave and running wave(γ≠1).In particular,for γ=1,the system only hosts a normal phase and a superradiant phase.In contrast,for γ≠1,the system features three distinctive phases:the normal phase(NP),superradiant phase 1(SR_(1)),and superradiant phase 2(SR_(2)).Importantly,the superradiance is subdivided into different types characterized by the photon phase.Furthermore,we determine perturbatively the phase boundary separating the normal phase and the superradiant phases,and find that there exists a competitive relationship of energy minimum on the overlapping region between SR_(1) and SR_(2).Interestingly,the transition between the normal phase to SR_(1) or SR_(2) is identified to be a second-order phase transition,while the transition between SR_(1) and SR_(2) is a first-order transition.When the first-order phase transition occurs,the phase of the photons changes abruptly from 0 to π/2.展开更多
Currently,the development of high-efficiency two-dimensional(2D)transistors is still hindered by the limited availability of suitable semiconductors and the contact resistance between the metal contact and the 2D semi...Currently,the development of high-efficiency two-dimensional(2D)transistors is still hindered by the limited availability of suitable semiconductors and the contact resistance between the metal contact and the 2D semiconductors.Endeavors to address these challenges are highly desired.In this study,we conducted a comprehensive exploration of the potential 2D transition metal dinitrides(TMN_(2)s,TM=all the 3d,4d and 5d transition metals)with hexagonal(h-)and trigonal(t-)phases through systematic first-principles calculations.Among all h-TMN_(2)s and t-TMN_(2)s structures,we identified 8 TMN_(2)s that exhibit dynamical and thermal stability at room temperature.Of these,the h-TiN_(2),h-ZrN_(2)and h-HfN_(2)arefound to be semiconductors,and their direct bang gap,calculated at the HSE06 level,are 1.48,1.96 and 2.64 eV,respectively.The electron and hole mobility(μ_(e)andμ_(h))of these three structures exceed 1×10^(4)and1×10^(3)cm^(2)·V^(-1)·s^(-1),respectively.Especially,theμeof h-TiN_(2)amounts to 2.5×10^(4)cm^(2)·V^(-1)·s^(-1),and theμhof h-ZrN_(2)reaches to 7.7×10^(3)cm^(2)·V^(-1)·s^(-1).Importantly,unlike the MoS_(2)system,h-TMN_(2)forms Ohm contacts with both transition metals(e.g.,Cu)and 2D metals(e.g.,graphene),with tunneling possibilities exceeding 50%in the Cu system.These outstanding intrinsic semiconductor properties and contact characteristics exhibited by h-TMN_(2)highlight the immense potential of transition metal dinitrides in driving the advancement of next-generation information devices.Our findings significantly broaden the range of 2D materials and provide valuable insights for the development of high-eficiency 2D information devices.展开更多
To address issues such as poor initial population diversity, low stability and local convergence accuracy, and easy local optima in the traditional Multi-Objective Artificial Hummingbird Algorithm (MOAHA), an Improved...To address issues such as poor initial population diversity, low stability and local convergence accuracy, and easy local optima in the traditional Multi-Objective Artificial Hummingbird Algorithm (MOAHA), an Improved MOAHA (IMOAHA) was proposed. The improvements involve Tent mapping based on random variables to initialize the population, a logarithmic decrease strategy for inertia weight to balance search capability, and the improved search operators in the territory foraging phase to enhance the ability to escape from local optima and increase convergence accuracy. The effectiveness of IMOAHA was verified through Matlab/Simulink. The results demonstrate that IMOAHA exhibits superior convergence, diversity, uniformity, and coverage of solutions across 6 test functions, outperforming 4 comparative algorithms. A Wilcoxon rank-sum test further confirmed its exceptional performance. To assess IMOAHA’s ability to solve engineering problems, an optimization model for a multi-track, multi-train urban rail traction power supply system with Supercapacitor Energy Storage Systems (SCESSs) was established, and IMOAHA was successfully applied to solving the capacity allocation problem of SCESSs, demonstrating that it is an effective tool for solving complex Multi-Objective Optimization Problems (MOOPs) in engineering domains.展开更多
Electrochemical water splitting represents a sustainable technology for hydrogen(H_(2))production.However,its large-scale implementation is hindered by the high overpotentials required for both the cathodic hydrogen e...Electrochemical water splitting represents a sustainable technology for hydrogen(H_(2))production.However,its large-scale implementation is hindered by the high overpotentials required for both the cathodic hydrogen evolution reaction(HER)and the anodic oxygen evolution reaction(OER).Transition metal-based catalysts have garnered significant research interest as promising alternatives to noble-metal catalysts,owing to their low cost,tunable composition,and noble-metal-like catalytic activity.Nevertheless,systematic reviews on their application as bifunctional catalysts for overall water splitting(OWS)are still limited.This review comprehensively outlines the principal categories of bifunctional transition metal electrocatalysts derived from electrospun nanofibers(NFs),including metals,oxides,phosphides,sulfides,and carbides.Key strategies for enhancing their catalytic performance are systematically summarized,such as heterointerface engineering,heteroatom doping,metal-nonmetal-metal bridging architectures,and single-atom site design.Finally,current challenges and future research directions are discussed,aiming to provide insightful perspectives for the rational design of high-performance electrocatalysts for OWS.展开更多
The dissolvable polysulfides and sluggish Li_2S conversion kinetics are acknowledged as two significant challenges in the application lithium-sulfur(Li-S)batteries.Herein,we introduce a dual-doping strategy to modulat...The dissolvable polysulfides and sluggish Li_2S conversion kinetics are acknowledged as two significant challenges in the application lithium-sulfur(Li-S)batteries.Herein,we introduce a dual-doping strategy to modulate the electronic structure of MoS_(2),thereby obtaining a multifunctional catalyst that serves as an efficient sulfur host.The W/V dual single-atomdoped MoS_(2)grown on carbon nanofibers(CMWVS)demonstrates a strong adsorption ability for lithium polysulfides,suppressing the shuttle effects.Additionally,the doping process also results in the phase transition from 2H-MoS_(2)to 1T-MoS_(2)and generates sufficient edge sulfur atoms,promoting the charge/electron transfer and enriching the reaction sites.All these merits contribute to the superior conversion reaction kinetics,leading to the outstanding Li-S battery performance.When fabricated as cathodes by compositing with sulfur,the CMWVS/S cathode delivers a high capacity of 1481.7 mAh g^(-1)at 0.1 C(1 C=1672 mAh g^(-1))and maintains 816.3 m Ah g^(-1)after 1000 cycles at 1.0 C,indicating outstanding cycling stability.Even under a high sulfur loading of 7.9 mg cm^(-2)and lean electrolyte conditions(E/S ratio of 9.0μL mg^(-1)),the cathode achieves a high areal capacity of 8.2 m Ah cm^(-2),showing great promise for practical Li-S battery applications.This work broadens the scope of doping strategies in transition-metal dichalcogenides by tailoring their electronic structures,providing insightful direction for the rational development of high-efficiency electrocatalysts for advanced Li-S battery applications.展开更多
The volume change behavior of natural gas hydrate-bearing sediment is essential as it influences settlement,strength,and stiffness,which directly affect the stability of hydrate reservoirs during hydrate extraction or...The volume change behavior of natural gas hydrate-bearing sediment is essential as it influences settlement,strength,and stiffness,which directly affect the stability of hydrate reservoirs during hydrate extraction or in response to environmental changes.The volume change is influenced not only by stress but also by the formation and dissociation of hydrates.This study adopted a customized apparatus for one-dimensional compression tests,allowing independent control of gas pressure and effective stress.Tests were conducted on samples with different hydrate saturations along various temperature-gas pressure-effective stress paths,yielding some conclusions related to compressibility and creep.An unusual phenomenon was observed under low-stress conditions:hydrate formation led to shrinkage rather than expansion.Three potential mechanisms behind this occurrence were discussed.As hydrate saturation increases,the yield stress rises while the compression and swelling indexes remain minimally affected.After hydrate dissociation,the compression curve of hydrate-bearing sediment drops to that of hydrate-free sediment.Once hydrate is formed,the compression curve of hydrate-free sediment gradually approaches that of hydrate-bearing sediment during the subsequent loading.Under low-stress conditions,the creep of both hydrate-free and hydrate-bearing sediments is very weak.However,when stress increases,significantly beyond the yield stress,the creep of both sediments increases significantly,with hydrate-bearing sediment exhibiting much greater creep than hydrate-free sediment.展开更多
基金Key Project of National Natural Science Foundation of China, No.41230632, No.71433008 Doctoral Project of Tianjin Normal University, No.52XB 1621Acknowledgments We thank Prof. Michael J. White in Brown University for the comments and suggestions on this research. We also thank the Writing Center in Brown University, Joan and John Kenower for the language revision.
文摘The floating population has become the main driver of urban population excessive growth in China＇s mega cities. Urban transit system （UTS） is a significant factor in population spatial distributions within urban areas, especially rapid and high-capacity transit systems. This paper analyzes the causal effects of the extension of expressways and subways between 2000 and 2010 in the Beijing Metropolitan Area （BMA）, focusing on the group differences between the local residents and the floating population. Due to the endogeneity of transportation improvements and population growth, Instrumental Variable （IV） regression model is applied to avoid this problem. The results show the local residents increased in the inner suburbs but decreased in the city center, while the floating population increased in the majority areas. IV regression results show that the extension of urban transit systems had statistically significant impacts on population growth across the BMA, The results also show that the extension of urban subway system had more effects on the floating population than the local residents across the BMA. It is mainly caused by the rather low fare of urban subway system. This implies that the excessive subsidy on urban subway system could result in ex- cessive floating population growth and residential differentiation, even residential segregation Hence, it is necessary to plan and design reasonable and scientific urban transit systems in order to advance reasonable population size and promote residential integration. Moreover, the regional analysis shows that the effects of urban transportation improvements on the local residents are not statistically significant in the inner suburbs. It implies that urban transportation improvements had limited effects on inducing people to move to suburban areas and controlling center city＇s population in Beijing. Therefore, it should be stressed the differenti- ated effects of urban transportation improvements on population distribution in the process of urban planning and population control.
基金Project(BE2010043) supported by the Technology Support Program of Jiangsu Province,ChinaProject(CXZZ13_0928) supported by the Graduate Education Innovation Project of Jiangsu Province,China
文摘The novel method to analyze metallic structure corrosion status was proposed in the presence of stray current in DC mass transit systems. Firstly, the characteristic parameter and the influence parameters for the corrosion status were determined. Secondly, an experimental system was established for simulating the corrosion process within the stray current interference. Then, a predictive model for the corrosion status was built, using a support vector machine(SVM) method and experimental data. The data were divided into two sets, including training set and testing set. The training set was used to generate the SVM model and the testing set was used to evaluate the predictive performance of the SVM model. The results show that the relationship between the characteristic parameter and the influence parameters is nonlinear and the SVM model is suitable for predicting the corrosion status.
文摘Nowadays,Rail Transit System has become one of the most important transportation means for the residents in Beijing.Construction of good urban rail transit landscape has also attracted increasing attentions from designers and residents.The paper tries to explain that by taking sustainable landscape technological means and including plant utilization into all components of Beijing rail transit system the surrounding environment and inner environment of the subways could be expected to be improved.
文摘The energy storage system charges the energy generated during braking and discharges it again when a vehicle accelerates on urban transit system. The energy storage system is considered to be one of the useful devices for energy storing and recycling. The energy storage system was developed and installed on the test track of Gyeongsan LRT in Korea. This paper presents the test plan and how much energy is saved by the energy storage system through the field test. When the energy storage system is on/off, the energy saving rate is obtained.
基金supported by the National Natural Science Foundation of China(72288101,72201029,and 72322022).
文摘Accurate origin–destination(OD)demand prediction is crucial for the efficient operation and management of urban rail transit(URT)systems,particularly during a pandemic.However,this task faces several limitations,including real-time availability,sparsity,and high-dimensionality issues,and the impact of the pandemic.Consequently,this study proposes a unified framework called the physics-guided adaptive graph spatial–temporal attention network(PAG-STAN)for metro OD demand prediction under pandemic conditions.Specifically,PAG-STAN introduces a real-time OD estimation module to estimate real-time complete OD demand matrices.Subsequently,a novel dynamic OD demand matrix compression module is proposed to generate dense real-time OD demand matrices.Thereafter,PAG-STAN leverages various heterogeneous data to learn the evolutionary trend of future OD ridership during the pandemic.Finally,a masked physics-guided loss function(MPG-loss function)incorporates the physical quantity information between the OD demand and inbound flow into the loss function to enhance model interpretability.PAG-STAN demonstrated favorable performance on two real-world metro OD demand datasets under the pandemic and conventional scenarios,highlighting its robustness and sensitivity for metro OD demand prediction.A series of ablation studies were conducted to verify the indispensability of each module in PAG-STAN.
文摘Traditionally, the process used by public transportation entities to determine the acquisition strategy for new vehicle asset is based upon a broad range of criteria. Vehicle cost has been cited as one of the more critical factors which decision makers consider. It is currently a common practice to consider other factors (life-cycle cost, fuel efficiency, vehicle reliability, environmental effects, etc.) that contribute to a more comprehensive approach. This study investigates the next generation of advancements in decision making tools in the area of the application of methods to quantify and manage uncertainty. In particular, the uncertainty comes from the public policy arena where future policy and regulations are not always based upon logical and predictable processes. The fleet decision making process in most governmental agencies is a very complex and interdependent activity. There are always competing forces and agendas within the view of the decision maker. Rarely is the decision maker a single person although, within the transit environment, there is often one person charged with the responsibility of fleet management. The focus of this research examines the decision making of the general transit agency community via the development of an expert systems prototype tool. A computer-based prototype system is developed which provide an expert knowledge-based recommendation, based upon variable user inputs. The results shown in this study show that a decision making tool for the management of transit system alternate fuel vehicle assets can be modeled and tested. The direct users of this research are the transit agency administrations. The results can be used by the management teams as a reliable input to inform their urban transit buses expansion decision making process.
文摘Bus rapid transit (BRT) systems have been implemented in many cities over the past two decades. Widespread adoption of General Transit Feed Specification (GTFS), the deployment of high-fidelity bus GPS data tracking, and anonymized high-fidelity connected vehicle data from private vehicles have provided new opportunities for performance measures that can be used by both transit agencies and traffic signal system operators. This paper describes the use of trajectory-based data to develop performance measures for a BRT system in Indianapolis, Indiana. Over 3 million data records during the 3-month period between March and May 2022 are analyzed to develop visualizations and performance metrics. A methodology to estimate the average delay and schedule adherence is presented along a route comprised of 74 signals and 28 bus stations. Additionally, this research demonstrates how these performance measures can be used to evaluate dedicated and non-dedicated bus lanes with general traffic. Travel times and reliability of buses are compared with nearly 30 million private vehicle trips. Results show that median travel time for buses on dedicated bi-directional lanes is within one minute of general traffic and during peak periods the buses are often faster. Schedule adherence was observed to be more challenging, with approximately 3% of buses arriving within 1 minute on average during the 5AM hour and 5% of buses arriving 6 - 9 minutes late during the 5PM hour. The framework and performance measures presented in this research provide agencies and transportation professionals with tools to identify opportunities for adjustments and to justify investment decisions.
文摘In this research three new innovative concepts are introduced and developed: the first defined as Transit System Maturity Components (TSMC), the second referred to as Transit System Maturity Scale (TSMS) and the third labeled as Transit System Maturity Index (TSMI). The TSMC is meant to conceptualise the main strategic generic components characterising the maturity of transit systems. The TSMS is an S shaped scaling system for measuring maturity of transit system components. The TSMI presents an innovative index meant to assess the overall level of maturity of a city transit system. Such framework is envisaged to be used to determine and compare the overall maturity levels of transit systems in cities of the world as well as to act as a basis to identify strengths & gaps that need to be addressed/completed. Furthermore, it can also act as an ingredient in shaping and developing future road maps for transit system in cities across the world. The research concludes by demonstrating the applicability of TSMC, TSMS, and TSMI in conducting an initial assessment of the Transit System Maturity for the fast growing city of Dubai.
文摘A new transportation technology known as personal rapid transit （PRT） is being developed by multiple different companies around the world, and one system is under commercial operations in the United Kingdom. Each design is different, but they all share a need to operate many automated transit vehicles at very close headways. Safe operation will require a level of control an order of magnitude above any current transit system. As a result, new techniques will be needed for the development and testing of the mechanical and control systems. In this paper an apparatus for developing and testing a PRT vehicle control scheme is demonstrated. This system is composed of independent modules that represent virtual vehicles, a central control system, a man-machine interface and a monitoring device. It can be used to implement and to evaluate the designed vehicle control algorithm. The vehicle control algorithm is designed and simulated in a combined simulation platform that consists of Matlab/Simulink and Labview Simulation Interface Toolkit. Simple operational scenarios are proposed for the testing of the proposed vehicle control apparatus.
基金supported by the Young Scientists Promotion Fund of Natural Science Foundation of Guangdong Province(No.2023A1515030128)Natural Science Foundation of Guangdong Province(No.2024A1515011590)+1 种基金National Natural Science Foundation of China(No.81703438)CAMS Innovation Fund for Medical Sciences(No.2022-I2M-1-015).
文摘The phase transition among different solid forms of active pharmaceutical ingredients can significantly influence their physicochemical properties,potentially leading to clinical safety risks.However,phase transition mechanisms remain under explored,especially in multi-component drugs.Here we report a novel ciprofloxacin-diclofenac salt system and investigate phase transitions among its anhydrate,dihydrate,and methanol solvate forms.The study focused on the influence of water activity and solvent vapor conditions,elucidating the role of vip molecules in driving these transitions.These findings offer new insights into polymorphic phase transitions,advancing our understanding of stability and performance in pharmaceutical formulations.
基金funded by the National Key Research and Development Program of China(2022YFF1100501)the Postdoctoral Research Foundation of Shunde Innovation School of University of Science and Technology Beijing(2024BH002).
文摘A dietary transition from refined to whole grains would optimize grain processing,reduce food loss and emissions,and increase food nutritional contents.The results of systematical analysis and calculations in our study show that the average processing loss rate of grains including rice,wheat,and maize is approximately 4.1%in China due to the refinement,equivalent to an annual loss of around 13.3 Mt of grains.Furthermore,the refining process significantly reduces the nutritional contents of rice(51.6%),wheat flour(55.4%),and corn products(80.4%)mainly resulting from the removal of dietary fiber,minerals,and vitamins in refined grains.Replacing refined grains with whole grains in diets would lower agricultural carbon emissions by 2.7%,reducing agricultural water use by 4.3%,and saving arable land by 1,972,607 ha.Total environmental footprint could be reduced by 35%to 79%under three proposed scenarios.These findings indicate that shifting toward whole grain-based diets by Chinese consumers could reduce food losses,enhance human health,and improve environmental sustainability.This approach offers a promising strategy for transitioning towards more resilient and sustainable agri-food systems,benefiting human and planetary health.
基金supported by the National Research Council of Thailand(No.NRCT-5-RSA63004-16)Chiang Mai University.S.Pakluea acknowledges scholarship support from the Science Achievement Scholarship of Thailand(SAST).
文摘Terahertz(THz)radiation possesses unique properties that make it a promising light source for applications in various fields,particularly spectroscopy and imaging.Ongoing research and development in THz technology has focused on developing or improving THz sources,detectors,and applications.At the PBP-CMU Electron Linac Laboratory(PCELL)of the Plasma and Beam Physics Research Facility in Chiang Mai University,high-intensity THz radiation has been generated in the form of coherent transition radiation(TR)and investigated since 2006 for electron beams with energies ranging from 8 to 12 MeV.In this study,we investigate and optimize the coherent TR arising from short electron bunches with energies ranging from 8 to 22 MeV using an upgraded linear-accelerator system with a higher radio-frequency(RF)power system.This radiation is then transported from the accelerator hall to the experimental room,in which the spectrometers are located.Electron-beam simulations are conducted to achieve short bunch lengths and small transverse beam sizes at the TR station.Radiation properties,including the radiation spectrum,angular distribution,and radiation polarization,are thoroughly investigated.The electron-bunch length is evaluated using the measuring system.The radiation-transport line is designed to achieve optimal frequency response and high transmission efficiency.A radiation-transmission efficiency of approximately 80-90%can be achieved with this designed system,along with a pulse energy ranging from 0.17 to 0.25μJ.The expected radiation spectral range covers up to 2 THz with a peak power of 0.5-1.25 MW.This coherent,broadband,and intense THz radiation will serve as a light source for THz spectroscopy and THz time-domain spectroscopy applications at the PCELL in the near future.
基金supported by the National Natural Science Foundation of China(Grant numbers 52177112 and 52278419)the Chinese Academy of Engineering(Grant number 2022--XY-75).
文摘Within the transition process of urban rail transit systems,the challenges of high energy consumption,increasing carbon emissions,limited economic viability,and intricate risks emerge as significant hurdles.This paper proposes a novel energy utilization framework for the urban rail transit system that incorporates underground energy storage systems characterized by high resilience and low carbon.First,existing methods employed in urban rail transit are comprehensively reviewed.Then,a novel framework and strategic significance of the urban rail transit system incorporating underground energy storage systems are introduced.This integration effectively utilizes and manages diverse renewable energy sources and the available space resources.The viability is demonstrated through a case study by combining Nanjing metro.Finally,suggestions for research in pivotal areas are summarized.
基金supported by the National Natural Science Foundation of China(Nos.22273122,T2350009)the Guangdong Provincial Natural Science Foundation(No.2024A1515011504)computational resources and services provided by the national supercomputer center in Guangzhou.
文摘We investigate dynamical quantum phase transitions(DQPTs)in Marko-vian open quantum systems using a variational quantum simulation(VQS)algorithm based on quantum state diffusion(QSD).This approach reformulates the Lindblad master equation as an ensemble of pure-state trajectories,enabling efficient simula-tion of dissipative quantum dynam-ics with effectively reduced quantum resources.Focusing on the one-di-mensional transverse-field Ising mod-el(TFIM),we simulate quench dynamics under both local and global Lindblad dissipation.The QSD-VQS algorithm accurately captures the nonanalytic cusps in the Loschmidt rate function,and reveals their modulation by dissipation strength and system size.Notably,DQPTs are gradually suppressed under strong local dissipation,while they persist under strong global dissipation due to collective environmental effects.Benchmarking against exact Lindblad solutions confirms the high accuracy and scalability of our method.
基金supported by the National Natural Science Foundation of China(Grant Nos.12174055 and 11674058)the Natural Science Foundation of Fujian Province,China(Grant No.2020J01195)。
文摘We consider a Bose-Einstein condensate loaded inside an optical cavity and exposed to two crossed coherent pump fields with same imbalance parameter γ.We identify different effects between pure standing wave fields(γ=1)and the pump beams combining standing wave and running wave(γ≠1).In particular,for γ=1,the system only hosts a normal phase and a superradiant phase.In contrast,for γ≠1,the system features three distinctive phases:the normal phase(NP),superradiant phase 1(SR_(1)),and superradiant phase 2(SR_(2)).Importantly,the superradiance is subdivided into different types characterized by the photon phase.Furthermore,we determine perturbatively the phase boundary separating the normal phase and the superradiant phases,and find that there exists a competitive relationship of energy minimum on the overlapping region between SR_(1) and SR_(2).Interestingly,the transition between the normal phase to SR_(1) or SR_(2) is identified to be a second-order phase transition,while the transition between SR_(1) and SR_(2) is a first-order transition.When the first-order phase transition occurs,the phase of the photons changes abruptly from 0 to π/2.
基金financially supported by the National Natural Science Foundation of China(No.52171141)the Fund of Natural Science Special(Special Post)Research Foundation of Guizhou University(No.2023-032)the Fund of Research Foundation of Guizhou University(No.2024-33)
文摘Currently,the development of high-efficiency two-dimensional(2D)transistors is still hindered by the limited availability of suitable semiconductors and the contact resistance between the metal contact and the 2D semiconductors.Endeavors to address these challenges are highly desired.In this study,we conducted a comprehensive exploration of the potential 2D transition metal dinitrides(TMN_(2)s,TM=all the 3d,4d and 5d transition metals)with hexagonal(h-)and trigonal(t-)phases through systematic first-principles calculations.Among all h-TMN_(2)s and t-TMN_(2)s structures,we identified 8 TMN_(2)s that exhibit dynamical and thermal stability at room temperature.Of these,the h-TiN_(2),h-ZrN_(2)and h-HfN_(2)arefound to be semiconductors,and their direct bang gap,calculated at the HSE06 level,are 1.48,1.96 and 2.64 eV,respectively.The electron and hole mobility(μ_(e)andμ_(h))of these three structures exceed 1×10^(4)and1×10^(3)cm^(2)·V^(-1)·s^(-1),respectively.Especially,theμeof h-TiN_(2)amounts to 2.5×10^(4)cm^(2)·V^(-1)·s^(-1),and theμhof h-ZrN_(2)reaches to 7.7×10^(3)cm^(2)·V^(-1)·s^(-1).Importantly,unlike the MoS_(2)system,h-TMN_(2)forms Ohm contacts with both transition metals(e.g.,Cu)and 2D metals(e.g.,graphene),with tunneling possibilities exceeding 50%in the Cu system.These outstanding intrinsic semiconductor properties and contact characteristics exhibited by h-TMN_(2)highlight the immense potential of transition metal dinitrides in driving the advancement of next-generation information devices.Our findings significantly broaden the range of 2D materials and provide valuable insights for the development of high-eficiency 2D information devices.
基金by National Natural Science Foundation of China(62373142,62033014)Natural Science Foundation of Hunan Province(2025JJ70017,2022JJ50074).
文摘To address issues such as poor initial population diversity, low stability and local convergence accuracy, and easy local optima in the traditional Multi-Objective Artificial Hummingbird Algorithm (MOAHA), an Improved MOAHA (IMOAHA) was proposed. The improvements involve Tent mapping based on random variables to initialize the population, a logarithmic decrease strategy for inertia weight to balance search capability, and the improved search operators in the territory foraging phase to enhance the ability to escape from local optima and increase convergence accuracy. The effectiveness of IMOAHA was verified through Matlab/Simulink. The results demonstrate that IMOAHA exhibits superior convergence, diversity, uniformity, and coverage of solutions across 6 test functions, outperforming 4 comparative algorithms. A Wilcoxon rank-sum test further confirmed its exceptional performance. To assess IMOAHA’s ability to solve engineering problems, an optimization model for a multi-track, multi-train urban rail traction power supply system with Supercapacitor Energy Storage Systems (SCESSs) was established, and IMOAHA was successfully applied to solving the capacity allocation problem of SCESSs, demonstrating that it is an effective tool for solving complex Multi-Objective Optimization Problems (MOOPs) in engineering domains.
基金Supported by the National Natural Science Foundation of China(No.52273056)the Science and Technology Development Program of Jilin Province,China(No.YDZJ202501ZYTS305)。
文摘Electrochemical water splitting represents a sustainable technology for hydrogen(H_(2))production.However,its large-scale implementation is hindered by the high overpotentials required for both the cathodic hydrogen evolution reaction(HER)and the anodic oxygen evolution reaction(OER).Transition metal-based catalysts have garnered significant research interest as promising alternatives to noble-metal catalysts,owing to their low cost,tunable composition,and noble-metal-like catalytic activity.Nevertheless,systematic reviews on their application as bifunctional catalysts for overall water splitting(OWS)are still limited.This review comprehensively outlines the principal categories of bifunctional transition metal electrocatalysts derived from electrospun nanofibers(NFs),including metals,oxides,phosphides,sulfides,and carbides.Key strategies for enhancing their catalytic performance are systematically summarized,such as heterointerface engineering,heteroatom doping,metal-nonmetal-metal bridging architectures,and single-atom site design.Finally,current challenges and future research directions are discussed,aiming to provide insightful perspectives for the rational design of high-performance electrocatalysts for OWS.
基金supported by the National Natural Science Foundation of China(52402166)the Science and Technology Development Fund+2 种基金Macao SAR(0065/2023/AFJ,0116/2022/A3)the Australian Research Council(DE220100154)the Natural Science Foundation of Guangdong Province(2025A1515011120)。
文摘The dissolvable polysulfides and sluggish Li_2S conversion kinetics are acknowledged as two significant challenges in the application lithium-sulfur(Li-S)batteries.Herein,we introduce a dual-doping strategy to modulate the electronic structure of MoS_(2),thereby obtaining a multifunctional catalyst that serves as an efficient sulfur host.The W/V dual single-atomdoped MoS_(2)grown on carbon nanofibers(CMWVS)demonstrates a strong adsorption ability for lithium polysulfides,suppressing the shuttle effects.Additionally,the doping process also results in the phase transition from 2H-MoS_(2)to 1T-MoS_(2)and generates sufficient edge sulfur atoms,promoting the charge/electron transfer and enriching the reaction sites.All these merits contribute to the superior conversion reaction kinetics,leading to the outstanding Li-S battery performance.When fabricated as cathodes by compositing with sulfur,the CMWVS/S cathode delivers a high capacity of 1481.7 mAh g^(-1)at 0.1 C(1 C=1672 mAh g^(-1))and maintains 816.3 m Ah g^(-1)after 1000 cycles at 1.0 C,indicating outstanding cycling stability.Even under a high sulfur loading of 7.9 mg cm^(-2)and lean electrolyte conditions(E/S ratio of 9.0μL mg^(-1)),the cathode achieves a high areal capacity of 8.2 m Ah cm^(-2),showing great promise for practical Li-S battery applications.This work broadens the scope of doping strategies in transition-metal dichalcogenides by tailoring their electronic structures,providing insightful direction for the rational development of high-efficiency electrocatalysts for advanced Li-S battery applications.
基金supported by the National Natural Science Foundation of China(Grant No.42171135)the Science and Technology Program of CNOOC Research Institute(Grant No.2023OTKK03)the“CUG Scholar”Scientific Research Funds at China University of Geosciences(Project No.2022098).
文摘The volume change behavior of natural gas hydrate-bearing sediment is essential as it influences settlement,strength,and stiffness,which directly affect the stability of hydrate reservoirs during hydrate extraction or in response to environmental changes.The volume change is influenced not only by stress but also by the formation and dissociation of hydrates.This study adopted a customized apparatus for one-dimensional compression tests,allowing independent control of gas pressure and effective stress.Tests were conducted on samples with different hydrate saturations along various temperature-gas pressure-effective stress paths,yielding some conclusions related to compressibility and creep.An unusual phenomenon was observed under low-stress conditions:hydrate formation led to shrinkage rather than expansion.Three potential mechanisms behind this occurrence were discussed.As hydrate saturation increases,the yield stress rises while the compression and swelling indexes remain minimally affected.After hydrate dissociation,the compression curve of hydrate-bearing sediment drops to that of hydrate-free sediment.Once hydrate is formed,the compression curve of hydrate-free sediment gradually approaches that of hydrate-bearing sediment during the subsequent loading.Under low-stress conditions,the creep of both hydrate-free and hydrate-bearing sediments is very weak.However,when stress increases,significantly beyond the yield stress,the creep of both sediments increases significantly,with hydrate-bearing sediment exhibiting much greater creep than hydrate-free sediment.
