| 1. |
- Wu, Pan, et al.
(författare)
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Revealing the determinants of the intermodal transfer ratio between metro and bus systems considering spatial variations
- 2022
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Ingår i: Journal of Transport Geography. - : Elsevier BV. - 0966-6923. ; 104
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Tidskriftsartikel (refereegranskat)abstract
- Buses and metros are two main public transit modes, and these modes are crucial components of sustainable transportation systems. Promoting reciprocal integration between bus and metro systems requires a deep understanding of the effects of multiple factors on transfers among integrated public transportation transfer modes, i.e., metro-to-bus and bus-to-metro. This study aims to reveal the determinants of the transfer ratio between bus and metro systems and quantify the associated impacts. The transfer ratio between buses and metros is identified based on large-scale transaction data from automated fare collection systems. Meanwhile, various influencing factors, including weather, socioeconomic, the intensity of business activities, and built environment factors, are obtained from multivariate sources. A multivariate regression model is used to investigate the associations between the transfer ratio and multiple factors. The results show that the transfer ratio of the two modes significantly increases under high temperature, strong wind, rainfall, and low visibility. The morning peak hours attract a transfer ratio of up to 57.95%, and the average hourly transfer volume is 0.94 to 1.38 times higher at this time than in other periods. The intensity of business activities has the most significant impact on the transfer ratio, which is approximately 1.5 to 15 times that of the other independent variables. Moreover, an adaptative geographically weighted regression is utilized to investigate the spatial divergences of the influences of critical factors on the transfer ratio. The results indicate that the impact of a factor presents spatial heterogeneity and even shows opposite effects (in terms of positive and negative) on the transfer ratio in different urban contexts. For example, among the related socioeconomic variables, the impact of the housing price on the downtown transfer ratio is larger than that in the suburbs. Crowd density positively influences the transfer ratio at most stations in the northern region, whereas it shows negative results in the southern region. These findings provide valuable insights for public transportation management and promote the effective integration of bus and metro systems to provide enhanced transfer services.
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| 2. |
- Gao, Zhaoju, et al.
(författare)
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Short-chain ligand achieves ultra-stable CsPbX3 perovskite quantum dots for white light-emitting diodes
- 2024
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 124:4
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Tidskriftsartikel (refereegranskat)abstract
- All-inorganic perovskite quantum dots (PeQDs) have aroused great research interest in white light-emitting diodes (WLED) due to their excellent optoelectronic properties, but the poor stability, caused by dynamically binding long-chain capping ligands, hinders their future practical applications. To address this issue, here, we exploit short-chain butyric acid (BA) to replace long-chain oleic acid (OA) as capping ligand of CsPbX3 PeQDs by a hot-injection method. The addition of BA not only makes the morphology of CsPbBr3 PeQDs uniform and improves the crystallinity but also effectively suppresses nonradiative recombination, achieving a near unit photoluminescence quantum yield of 96%. The BA capped CsPbBr3 PeQDs exhibit high stability up to 180 d stored in ambient environment and also significantly improved resistance against polar solvent, ultra-violet lamp irradiation, and heat, which is rationalized by the strong binding capacity and shortened distance of BA to the PeQDs through ab initio calculations. Furthermore, by combining green-emission CsPbBr3 and red-emission CsPbBr0.8I2.2 PeQDs with blue GaN chip, we achieved WLEDs with excellent luminous properties, showing their great potential in practical application of wide-color-gamut display and lighting.
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| 3. |
- Yan, Junfang, et al.
(författare)
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Local adaptive sampling for an energy harvesting CO2 sensor
- 2011
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Ingår i: IET Conference Publications. - : IEEE. - 9781849194730
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Konferensbidrag (refereegranskat)abstract
- For a sensor network, energy limitation is always a key factor to affect the continuous work of a sensor node. A good idea is harvesting energy from the environment to support the node to work continuously. However, energy from environment is varied with time, weather and season. So in order to use the varied environment energy, it is necessary to find a way to achieve real-time monitoring and adaptive working. In this paper, an algorithm called "Adaptive Sampling" was proposed to adapt the sample mode to the present energy condition. And solar energy is proposed as the energy source to power the system. Simulation proves that the algorithm can make the C02 sensor flexibly achieve adaptive sampling under different energy condition with the least MSE 2.7767. This algorithm can be widely used in wireless sensor network power by energy harvesting for local adaptive sampling.
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| 4. |
- Cheng, Hao-Wen, et al.
(författare)
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Realizing Efficient Charge/Energy Transfer and Charge Extraction in Fullerene-Free Organic Photovoltaics via a Versatile Third Component
- 2019
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Ingår i: Nano letters (Print). - : AMER CHEMICAL SOC. - 1530-6984 .- 1530-6992. ; 19:8, s. 5053-5061
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Tidskriftsartikel (refereegranskat)abstract
- Solution-processed organic photovoltaics (OPVs) based on bulk-heterojunctions have gained significant attention to alleviate the increasing demend of fossil fuel in the past two decades. OPVs combined of a wide bandgap polymer donor and a narrow bandgap nonfullerene acceptor show potential to achieve high performance. However, there are still two reasons to limit the OPVs performance. One, although this combination can expand from the ultraviolet to the near-infrared region, the overall external quantum efficiency of the device suffers low values. The other one is the low open-circuit voltage (V-OC) of devices resulting from the relatively downshifted lowest unoccupied molecular orbital (LUMO) of the narrow bandgap. Herein, the approach to select and incorporate a versatile third component into the active layer is reported. A third component with a bandgap larger than that of the acceptor, and absorption spectra and LUMO levels lying within that of the donor and acceptor, is demonstrated to be effective to conquer these issues. As a result, the power conversion efficiencies (PCEs) are enhanced by the elevated short-circuit current and V-OC; the champion PCEs are 11.1% and 13.1% for PTB7-Th:IEICO-4F based and PBDB-T:Y1 based solar cells, respectively.
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| 5. |
- Gao, D. -C, et al.
(författare)
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A GA-based NZEB-cluster planning and design optimization method for mitigating grid overvoltage risk
- 2022
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Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 243
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Tidskriftsartikel (refereegranskat)abstract
- Net-zero energy buildings (NZEBs) are considered as a promising method to mitigating the energy problems. Due to the intermittent characteristics of renewable energy (e.g., solar energy), NZEBs need to frequently exchange energy with the grid, which imposes severe negative impacts on the grid especially the overvoltage risk. Both planning and design are essential for reducing NZEB connected grid overvoltage, but most existing studies isolated the efforts from planning to design, thereby failing to achieve the best cumulative result. More importantly, existing studies oversimplified overvoltage quantification by using aggregated power interactions to represent overvoltage risk, which cannot consider the complex voltage influences among grid nodes. Due to the isolated efforts and the quantification oversimplification, existing studies can hardly achieve overvoltage risk minimization. Therefore, this study proposes a novel GA (genetic algorithm)-based method in which the key planning and design parameters are optimized sequentially for mitigating the overvoltage risk. Meanwhile, distribution network model has been adopted to precisely quantify the grid overvoltage. The study results show that the proposed method is highly effective in reducing NZEB cluster connected grid overvoltage risk. The proposed method can be used in practice for improving NZEB cluster planning and system design as grid interaction is considered. © 2021 Elsevier Ltd
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| 6. |
- Han, Meng, et al.
(författare)
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Experimental study of the effect of air split ratio on thermoacoustic instability in a centrally-staged swirl burner
- 2022
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Ingår i: Physics of Fluids. - : AIP Publishing. - 1070-6631 .- 1089-7666. ; 34:6
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Tidskriftsartikel (refereegranskat)abstract
- This study focuses on one of the critical design parameters of lean premixed (LPM) combustors-the air split ratio (ASR) between the pilot and main stages. The effect of the air split ratio on thermoacoustic instability is experimentally studied based on a centrally staged model combustor. It is found that the thermoacoustic instability is suppressed with the ASR higher than 20%. The acoustic modes of ASR lower than 20% are dominated by the main stage mode, while the others are controlled by the pilot stage mode. The time-averaged flame shapes and the flame dynamics are processed and discussed. With the increase in ASR, the pilot flame becomes longer, whereas the main flame becomes shorter. Meanwhile, the pilot and main flames become less separated. Moreover, the flame in the outer shear layer (OSL) is extinguished, which is the key to suppressing the thermoacoustic instability. The flame with lower ASR exhibits large-scale periodic axial motion of flame dynamics. The flow fields of ASR = 15% (unstable) and ASR = 30% (stable) are analyzed and discussed to help reveal the differences in thermoacoustic instability between the two cases. It is found that the primary recirculation zone is smaller with ASR = 30%. Higher vorticity and strain rate distributions found in the OSL are believed to quench the flame there. The present study illustrates that a higher air split ratio improves the thermoacoustic stability, which is helpful in designing LPM combustors.
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