| 1. |
- Ye, Xiaoling, et al.
(författare)
-
Advances in the Field of Two-Dimensional Crystal-Based Photodetectors
- 2023
-
Ingår i: Nanomaterials. - : MDPI. - 2079-4991. ; 13:8
-
Forskningsöversikt (refereegranskat)abstract
- Two-dimensional (2D) materials have sparked intense interest among the scientific community owing to their extraordinary mechanical, optical, electronic, and thermal properties. In particular, the outstanding electronic and optical properties of 2D materials make them show great application potential in high-performance photodetectors (PDs), which can be applied in many fields such as high-frequency communication, novel biomedical imaging, national security, and so on. Here, the recent research progress of PDs based on 2D materials including graphene, transition metal carbides, transition-metal dichalcogenides, black phosphorus, and hexagonal boron nitride is comprehensively and systematically reviewed. First, the primary detection mechanism of 2D material-based PDs is introduced. Second, the structure and optical properties of 2D materials, as well as their applications in PDs, are heavily discussed. Finally, the opportunities and challenges of 2D material-based PDs are summarized and prospected. This review will provide a reference for the further application of 2D crystal-based PDs.
|
|
| 2. |
- Liu, Jianrong, et al.
(författare)
-
Analysis of older people's walking behavioral intention with the extended theory of planned behavior
- 2022
-
Ingår i: Journal of Transport and Health. - : Elsevier BV. - 2214-1405. ; 26
-
Tidskriftsartikel (refereegranskat)abstract
- Introduction: Walking is a vital part of an older person's daily routine. It is critical to get insight into the determinants of older people's behavioral intention (BI) to walk in the neighborhood to encourage walking among them. However, research on older people's walking habits is lacking, particularly in developing countries like China. Methods: 501 complete responses were collected from a face-to-face survey conducted in Nanjing City. Four models were analyzed and compared in this paper. The theory of planned behavior (TPB) was examined in Model 1. The descriptive norm (DN) was added to the TPB in Model 2. Walking environment components were added to the TPB in Model 3. The TPB was supplemented with DN and walking environment constructs in Model 4. Results: Model 1 and Model 2 explain 71.3% and 74.9% of the variance in BI, respectively, meaning that the explanatory power increases by 3.6% when DN is taken into account. Model 3 explains 80.2% of the variance in BI, implying that when the walking environment constructs are included, the explanatory power increases by 8.9%. Model 4 has the greatest explanatory power (82.0%) on BI. Attitude (ATT), perceived behavioral control (PBC), and DN have significant associations with older people's BI, whereas subjective norm (SN) does not. In terms of constructs of the walking environment, perceived comfort has a significant association with behavioral intention, but perceived safety does not. Conclusions: How others act around an individual, other than how they approve of that individual's actions, has a significant impact on older people's walking intentions. PBC is highly correlated with older people's BI. The findings also emphasize the need of improving the walking environment for older individuals.
|
|
| 3. |
- Wu, Pan, et al.
(författare)
-
A Low-Rank Bayesian Temporal Matrix Factorization for the Transfer Time Prediction Between Metro and Bus Systems
- 2024
-
Ingår i: IEEE Transactions on Intelligent Transportation Systems. - 1524-9050 .- 1558-0016. ; 25:7, s. 7206-7222
-
Tidskriftsartikel (refereegranskat)abstract
- Accurate transfer time prediction and future transfer time information are important for both public transport operators and passengers. However, existing studies cannot effectively manage high-dimensional transfer time data, capture the complex nonlinearity of transfer time, or provide accurate transfer time information. This study provides a reliable prediction model called low-rank Bayesian temporal matrix factorization (LBTMF) to address these challenges. First, on the basis of a high-dimensional spatiotemporal matrix of transfer time data, we develop a low-rank temporal-regularized matrix factorization-based imputation module to capture spatial and temporal characteristics to replace missing transfer time data. Second, to further predict the transfer time with the imputation of missing data, we propose the spatiotemporal-based Bayesian temporal matrix factorization prediction module to recover hourly and daily regular characteristics to predict the transfer time at different metro stations during various periods. Finally, the comprehensive experimental findings suggest that the LBTMF model outperforms other excellent approaches in terms of imputation efficiency, prediction accuracy, and robustness.
|
|
| 4. |
- Ye, Xiaoling, et al.
(författare)
-
High Performance Self-Powered Photodetectors Based on Graphene Nanoribbons/Al2O3/InGaZnO Heterojunctions
- 2024
-
Ingår i: IEEE Photonics Journal. - : Institute of Electrical and Electronics Engineers (IEEE). - 1943-0655. ; 16:3
-
Tidskriftsartikel (refereegranskat)abstract
- Self-powered photodetectors which operate without external power sources hold immense promise in future photodetection systems. To achieve high-performance self-powered optoelectronic devices, efficient electron-hole pair separation is critical to generate high photocurrents. In this work, we successfully synthesized semiconducting graphene nanoribbons (GNRs) with a direct bandgap of 1.80 eV and employed them to construct a high-performance GNR/Al2O3/IGZO heterostructure photodetector. The built-in electric field in the heterojunctions enables this photodetector to exhibit remarkable performance, showing a responsivity of up to 68 mA/W, a detectivity of 8.34 x 1010 Jones, and rapid response times of 21/20 ms at zero bias. Furthermore, the photodetector features a wide spectral detection range of 405 to 1550 nm. These results highlight the promising potential of GNR/IGZO p-n heterojunction-based self-powered photodetectors in optoelectronic applications.
|
|
| 5. |
- Ding, Pengji, et al.
(författare)
-
Femtosecond laser-induced quantum-beat superfluorescence of atomic oxygen in a flame
- 2021
-
Ingår i: Physical Review A. - 2469-9926. ; 104:3
-
Tidskriftsartikel (refereegranskat)abstract
- Among different approaches to generate mirrorless lasing, resonant multiphoton pumping of gas constituents by deep-UV laser pulses exhibits so far the highest efficiency and produces measurable lasing energies, but the underlying mechanism was not yet fully settled. Here, we report lasing generation from atomic oxygen in a methane-air flame via femtosecond two-photon excitation. Temporal profiles of the lasing pulses were measured for varying concentrations of atomic oxygen, which shows that the peak intensity and time delay of the lasing pulse approximately scales as N and 1/N, respectively, where N represents the concentration. These scaling laws match well with the prediction of oscillatory superfluorescence (SF), indicating that the lasing we observed is essentially SF rather than amplified spontaneous emission. In addition, the quantum-beating effect was also observed in the time-resolved lasing pulse. A theoretical simulation based on nonadiabatic Maxwell-Bloch equations well reproduces the experimental observations of the temporal dynamics of the lasing pulses. These results on fundamentals should be beneficial for the better design and applications of lasing-based techniques.
|
|
| 6. |
- Kou, Dan, et al.
(författare)
-
Peatland Heterogeneity Impacts on Regional Carbon Flux and Its Radiative Effect Within a Boreal Landscape
- 2022
-
Ingår i: Journal of Geophysical Research: Biogeosciences. - 2169-8953. ; 127:9
-
Tidskriftsartikel (refereegranskat)abstract
- Peatlands, with high spatial variability in ecotypes and microforms, constitute a significant part of the boreal landscape and play an important role in the global carbon (C) cycle. However, the effects of this peatland heterogeneity within the boreal landscape are rarely quantified. Here, we use field-based measurements, high-resolution land cover classification, and biogeochemical and atmospheric models to estimate the atmosphere-ecosystem C fluxes and the corresponding radiative effect (RE) for a boreal landscape (Kaamanen) in northern Finland. Our result shows that the Kaamanen catchment currently functioned as a sink of carbon dioxide (CO2) and a source of methane (CH4). Peatlands (26% of the area) contributed 22% of the total CO2 uptake and 89% of CH4 emissions; forests (61%) accounted for 78% of CO2 uptake and offset 6% of CH4 emissions; water bodies (13%) offset 7% of CO2 uptake and contributed 11% of CH4 emissions. The heterogeneity of peatlands accounted for 11%, 88%, and 75% of the area-weighted variability (deviation from the area-weighted mean among different land cover types (LCTs) within the catchment) in CO2 flux, CH4 flux, and the combined RE of CO2 and CH4 exchanges over the 25-year time horizon, respectively. Aggregating peatland LCTs or misclassifying them as nonpeatland LCTs can significantly (p < 0.05) bias the regional CH4 exchange and RE estimates, while differentiating between drier noninundated and wetter inundated peatlands can effectively reduce the bias. Current land cover products lack such details in peatland heterogeneity, which would be needed to better constrain boreal C budgets and global C-climate feedbacks.
|
|
| 7. |
- Lin, Peiqun, et al.
(författare)
-
Bus timetable optimization model in response to the diverse and uncertain requirements of passengers for travel comfort
- 2023
-
Ingår i: Electronic Research Archive. - : American Institute of Mathematical Sciences (AIMS). - 2688-1594. ; 31:4, s. 2315-2336
-
Tidskriftsartikel (refereegranskat)abstract
- Most existing public transit systems have a fixed dispatching and service mode, which cannot effectively allocate resources from the perspective of the interests of all participants, resulting in resource waste and dissatisfaction. Low passenger satisfaction leads to a considerable loss of bus passengers and further reduces the income of bus operators. This study develops an optimization model for bus schedules that considers vehicle types and offers two service levels based on heterogeneous passenger demands. In this process, passenger satisfaction, bus company income, and government subsidies are considered. A bilevel model is proposed with a lower-level passenger ride simulation model and an upper-level multiobjective optimization model to maximize the interests of bus companies, passengers, and the government. To verify the effectiveness of the proposed methodology, a real-world case from Guangzhou is presented and analyzed using the nondominated sorting genetic algorithm-II (NSGA-II), and the related Pareto front is obtained. The results show that the proposed bus operation system can effectively increase the benefits for bus companies, passengers, and the government
|
|
| 8. |
- Liu, Jianrong, et al.
(författare)
-
Impact of COVID-19 on adolescent travel behavior
- 2022
-
Ingår i: Journal of Transport and Health. - : Elsevier BV. - 2214-1405. ; 24
-
Tidskriftsartikel (refereegranskat)abstract
- Introduction: The outbreak of COVID-19 has significantly impacted travel behavior. However, few studies have analyzed the impact of COVID-19 on adolescent travel behavior. This article analyzed the impact of COVID-19 on adolescent travel behavior using questionnaire survey data. Methods: This paper first used confirmatory factor analysis (CFA) to explore the psychological factors related to the adolescents' perceptions about the severity of COVID-19. The study then established a logit model to study the effects of COVID-19 in different phases (before, during, and after the epidemic peak), demographic characteristics, and the role of psychological factors on their travel behavior. Results: The results show that the phase of COVID-19 did not significantly impact the adolescents' choice of short-distance travel. The frequency of outings per week, the number of exercise sessions per week, and willingness to travel by public transportation decreased significantly in the outbreak phase. Meanwhile, the perception of the severity of COVID-19 significantly impacted adolescent travel behavior. Conclusion: This research demonstrates that COVID-19 has led adolescents to reduce their frequency of outings, and they try not to use public transportation. Adolescents appear to be traveling more cautiously in the outbreak phase and the post-epidemic phase.
|
|
| 9. |
- Liu, Mingyang, et al.
(författare)
-
A numerical study of snow accumulation on the bogies of high-speed trains based on coupling improved delayed detached eddy simulation and discrete phase model
- 2019
-
Ingår i: Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit. - : SAGE Publications. - 0954-4097 .- 2041-3017. ; 233:7, s. 715-730
-
Tidskriftsartikel (refereegranskat)abstract
- A numerical simulation method based on the improved delayed detached eddy simulation coupled with a discrete phase model is used to study the influence of the snow on the performance of bogies of a high-speed train running in snowy weather. The snow particle trajectories, mass of snow packing on the bogie, and thickness of snow accumulation have been analyzed to investigate the flow mechanisms of snow accumulation on different parts of the bogies. The results show that the snow accumulation on the first bogie of the head vehicle is almost the same as that of the second bogie, but the total accumulated snow on the top side of the second bogie is more than 74% higher than that of the first bogie. Among all the components of the bogies, the motors were found to be strongly influenced by the snow accumulation. The underlying flow mechanisms responsible for the snow accumulations are discussed.
|
|
| 10. |
- Liu, Mingyang, et al.
(författare)
-
A numerical study on water spray from wheel of high-speed train
- 2020
-
Ingår i: Journal of Wind Engineering and Industrial Aerodynamics. - : Elsevier BV. - 0167-6105. ; 197
-
Tidskriftsartikel (refereegranskat)abstract
- The influence of water spray from wheels on the ice accumulation in the bogie regions of high-speed train has been studied using the coupling numerical methods of improved delayed detached eddy simulation (IDDES) and Lagrangian Model. The rotation of the wheels was simulated using the moving overset grid technique. The flow field, spatial distribution and surface distribution of droplets on the bogies have been analysed to identify the effect of various speed on the movement of droplets. The results show that the inlet speed between 160 km/h and 250 km/h will lead to the most severe influence on water spray from wheel in the whole bogie regions. A large amount of water droplets gathering on the surface of the bogies and bogie cavities is likely to cause severe ice accretion. The influence of water spray for high-speed train decreases rapidly at the speed of 300 km/h and changes a little as the speed continues to increase. Among all the components of the bogie, the brake clamp is most affected by droplets. Furthermore, the droplets were found to have a severe effect on the draft sill and air spring.
|
|
