| 1. |
- Wang, Zhen, et al.
(författare)
-
Modeling and field experiments on autonomous vehicle lane changing with surrounding human-driven vehicles
- 2021
-
Ingår i: Computer-Aided Civil and Infrastructure Engineering. - : Wiley. - 1093-9687 .- 1467-8667. ; 36:7, s. 877-889
-
Tidskriftsartikel (refereegranskat)abstract
- Autonomous vehicle (AV) technology is widely studied in both industrial and academic communities since it is regarded as a promising means for improving transportation safety and efficiency. Lane changing is a critical link for higher-level AV operations. However, few studies on AV lane changing consider the dynamics of surrounding vehicles, particularly in a mixed traffic environment including human-driven vehicles (HVs). Therefore, this article presents a dynamic lane-changing model for AV incorporating human driver behavior in mixed traffic. The proposed model includes four key components: car following (and lane keeping), lane-changing decision, dynamic trajectory generation, and model predictive control (MPC)-based trajectory tracking. AV longitudinal control algorithm is also depicted in detail in this article. Field experiments are conducted on a large-scale test track to test and validate the proposed model. An AV and three HVs are used in the lane-changing experiments. Different human driver behaviors are considered in the experiment settings. Experimental results show that the proposed lane-changing model can complete lane-changing maneuvers efficiently when HVs are cooperative and can also robustly abort them when HVs are uncooperative. Compared with the measured human lane-changing maneuvers, AV lane-changing maneuvers from the proposed model are more comfortable and safer.
|
|
| 2. |
- Tang, Shengwen, et al.
(författare)
-
Continuous monitoring for leaching of calcium sulfoaluminate cement pastes incorporated with ZnCl 2 under the attacks of chloride and sulfate
- 2019
-
Ingår i: Chemosphere. - : Elsevier BV. - 0045-6535 .- 1879-1298. ; 223, s. 91-98
-
Tidskriftsartikel (refereegranskat)abstract
- Ionic zinc is considered as an environmental pollutant. This work systematically investigated leaching mechanisms of calcium sulfoaluminate cement (CSA) pastes incorporated with/without ZnCl 2 under the attacks of chloride and/or sulfate. The leaching behaviors of CSA pastes in the leaching solution are in-situ and continuously monitored by innovative non-contact electrical impedance measurement (NCEIM) and pH meter. The dissolution and diffusion during the leaching process are experimentally identified. Other techniques are also performed to verify the finding of NCEIM: the ion chromatograph and inductively coupled plasma optical emission spectrometer reveal the leaching or decomposition sequence of CSA pastes during the leaching process. Besides, results from XRD and SEM techniques demonstrate that main solid products in CSA pastes are ettringite and calcium monosulfoaluminate hydrates. The incorporation of Zn in the pastes has great impact on the decomposition of CSA pastes in the temperature elevation. External chloride and/or sulfate attacks significantly alter the pore structure of CSA pastes during the leaching process.
|
|
| 3. |
- Zhao, Xiangmo, et al.
(författare)
-
Field experiments on longitudinal characteristics of human driver behavior following an autonomous vehicle
- 2020
-
Ingår i: Transportation Research, Part C: Emerging Technologies. - : Elsevier BV. - 0968-090X. ; 114, s. 205-224
-
Tidskriftsartikel (refereegranskat)abstract
- Although mixed traffic, including both autonomous vehicles (AV) and human-driven vehicles (HV), is expected to prevail in the foreseeable future, our current understanding of the longitudinal characteristics of mixed traffic is limited and, in particular, lacks evidence from field experiments. To bridge this gap, we designed and conducted a set of field experiments to reveal differences in car-following behaviors between a human driver following-AV and following-HV on both constant speed traffic characteristics with discrete speeds ({10,20,…,60}km/h) and dynamic car-following behaviors with continuous speeds (within 0–60 km/h) in both the indifferentiable and differentiable appearance settings of the AV. We recruited 10 drivers for the experiment (14 runs for each driver and collected position and speed data of the tested vehicles along their complete trajectories based on vehicle gaps, headways, and standard deviations of vehicle speed. A K-means clustering algorithm was applied to classify drivers based on their responses in following-AV vs. following-HV with both constant speed and dynamic speed characteristics. The analyses of the differentiable appearance setting show that different drivers exhibit different behaviors in following-AV vs. following-HV: some are AV-believers, some are AV-skeptics, and the others are insensitive. Yet in the indifferentiable appearance setting, there is no significant difference between following a lead AV and following a lead HV. This reveals that drivers’ response to the lead vehicle depends on their subjective trusts on AV technologies rather than the actual driving behavior. The results suggest that, depending on the characteristics and composition of the drivers, classic car-following behavior in pure HV traffic may need to be updated for modeling mixed traffic in the near future.
|
|
| 4. |
- Hu, Chichun, et al.
(författare)
-
Experimental Study of Dowel Bar Alternatives Based on Similarity Model Test
- 2017
-
Ingår i: Advances in Materials Science and Engineering. - : Hindawi Limited. - 1687-8434 .- 1687-8442.
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, a small-scaled accelerated loading test based on similarity theory and Accelerated Pavement Analyzer was developed to evaluate dowel bars with different materials and cross-sections. Jointed concrete specimen consisting of one dowel was designed as scaled model for the test, and each specimen was subjected to 864 thousand loading cycles. Deflections between jointed slabs were measured with dial indicators, and strains of the dowel bars were monitored with strain gauges. The load transfer efficiency, differential deflection, and dowel-concrete bearing stress for each case were calculated from these measurements. The test results indicated that the effect of the dowel modulus on load transfer efficiency can be characterized based on the similarity model test developed in the study. Moreover, round steel dowel was found to have similar performance to larger FRP dowel, and elliptical dowel can be preferentially considered in practice.
|
|
| 5. |
- Shao, Jun, et al.
(författare)
-
Photoluminescence probing of interface evolution with annealing in InGa(N)As/GaAs single quantum wells
- 2015
-
Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 118:16, s. 165305-
-
Tidskriftsartikel (refereegranskat)abstract
- The effects of thermal annealing on the interfaces of InGa(N)As/GaAs single quantum wells(SQWs) are investigated by excitation-, temperature-, and magnetic field-dependent photoluminescence(PL). The annealing at 750 °C results in more significant blueshift and narrowing to the PLpeak than that at 600 °C. Each of the PL spectra can be reproduced with two PL components: (i)the low-energy component (LE) keeps energetically unchanged, while the high-energy component(HE) moves up with excitation and shows at higher energy for the In0.375Ga0.625As/GaAs butcrosses over with the LE at a medium excitation power for the In0.375Ga0.625N0.012As0.988/GaAsSQWs. The HE is broader than the corresponding LE, the annealing at 750 °C narrows the LE andHE and shrinks their energetic separation; (ii) the PL components are excitonic, and the InGaNAsshows slightly enhanced excitonic effects relative to the InGaAs SQW; (iii) no typical S-shape evolutionof PL energy with temperature is detectable, and similar blueshift and narrowing are identifiedfor the same annealing. The phenomena are mainly from the interfacial processes. Annealingimproves the intralayer quality, enhances the interfacial In-Ga interdiffusion, and reduces the interfacialfluctuation. The interfacial interdiffusion does not change obviously by the small N contentand hence similar PL-component narrowing and blueshift are observed for the SQWs after a nominallyidentical annealing. Comparison with previous studies is made and the PL measurementsunder different conditions are shown to be effective for probing the interfacial evolution in QWs.
|
|
| 6. |
- Zhao, Shengzhong, et al.
(författare)
-
Theoretical and numerical study on smoke descent during tunnel fires under natural ventilation condition
- 2023
-
Ingår i: Tunnelling and Underground Space Technology. - : Elsevier Ltd. - 0886-7798 .- 1878-4364. ; 142
-
Tidskriftsartikel (refereegranskat)abstract
- The smoke stratification and the smoke descent along a tunnel are of the utmost importance for personnel evacuation. The paper investigates the smoke descent along a tunnel during a naturally ventilated tunnel fire. A theoretical model is developed to predict the smoke depth below the ceiling along the tunnel. A series of numerical simulations of full-scale tunnel fires are conducted to compare with the developed model, and some coefficients such as the entrainment coefficient are determined from the simulation results. The concepts of critical moment and critical distance are proposed to characterize the smoke descent along the tunnel. The results show that as the smoke spreads longitudinally, the smoke depth below the tunnel ceiling continuously increases. The temperature decay along the tunnel due to heat losses and air entrainment at the smoke layer interface is considered as the main parameter for the smoke descent. After the vitiated air returns back to the fire source, the smoke stratification in the entire tunnel will be significantly reduced. The smoke layer depth along the tunnel based on the temperature distribution is relatively stable in the process of smoke development, which is not sensitive to the HRR, but influenced by the tunnel width, and this method could only be used before the critical moment. The outcomes of this study could provide references for a better understanding of smoke movement in naturally ventilated tunnels and provide technical guidelines for fire safety designers.
|
|
| 7. |
- Liu, Ruixu, et al.
(författare)
-
Configuration Optimization of Virtual Inertia Considering Spatial Distribution Characteristics of Frequency
- 2024
-
Ingår i: Dianli Xitong Zidonghua/Automation of Electric Power Systems. - : Automation of Electric Power Systems Press. - 1000-1026. ; 48:8, s. 122-130
-
Tidskriftsartikel (refereegranskat)abstract
- The high proportion of power electronic equipment connected to the grid changes the frequency response characteristics of the power system, resulting in significant frequency dynamic heterogeneity of each node, leading to problems such as low system inertia and weak frequency stability. The virtual inertia provided by the power electronic equipment is one of the effective ways to improve frequency stability. In order to improve the frequency response performance of the new power system dominated by renewable energy sources, a configuration optimization method of virtual inertia considering the spatial distribution difference of the system frequency response is proposed. Firstly, based on the frequency divider theory, a system frequency response model reflecting the difference characteristics of the spatial distribution of frequency is constructed. Secondly, in order to quantitatively describe the influence of inertia distribution on nodal frequency response, the deviation indices of nodal inertia and nodal kinetic energy are proposed. Then, considering the spatial distribution characteristics of frequency, aiming at optimizing the energy imbalance of each node after the disturbance, a configuration optimization model of virtual inertia is established. Finally, the validity of the nodal inertia index and the improvement effect of the proposed virtual inertia configuration method on the nodal frequency stability of the system are verified by simulations.
|
|
| 8. |
- Zhao, Jinli, et al.
(författare)
-
Peer-to-Peer electricity trading of interconnected flexible distribution networks based on Non-Cooperative games
- 2023
-
Ingår i: International Journal of Electrical Power & Energy Systems. - : Elsevier Ltd. - 0142-0615 .- 1879-3517. ; 145
-
Tidskriftsartikel (refereegranskat)abstract
- With the integration of power electronic devices represented by soft open points (SOPs), distribution networks have gradually evolved into interconnected flexible distribution networks (FDNs). Considering the deregulation of electricity market and user privacy, multiple stakeholders have participated in the operation of FDNs. Peer-to-peer (P2P) electricity trading is promising to alleviate operational problems of interconnected FDNs. As multiple regions pursue the maximum profits individually, non-cooperative game methods can be utilized to realize fair profit allocation in P2P trading. In this paper, a non-cooperative game-based P2P trading method is proposed to meet the electricity trading needs of multi-region interconnected FDNs. First, based on non-cooperative games, a two-layer P2P electricity trading framework is established to realize cost reduction and voltage profile improvement of multi-region interconnected FDNs. Then, a P2P trading adjustment mechanism is designed to improve the operational profits of SOP, in which spatial active power trading adjustment, temporal dispatching of energy storage (ES) link and reactive power support are incorporated. Finally, the effectiveness of the proposed method is verified based on a practical distribution network with four-terminal SOP in Tianjin. The results show that the proposed P2P electricity trading method can promote the economic operation performance of interconnected FDNs and improve the operational profit of SOP.
|
|
