| 1. |
- Chen, Zeyuan, et al.
(author)
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Survival in the Tropics despite isolation, inbreeding and asexual reproduction : insights from the genome of the world's southernmost poplar (Populus ilicifolia)
- 2020
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In: The Plant Journal. - : Wiley. - 0960-7412 .- 1365-313X. ; 103:1, s. 430-442
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Journal article (peer-reviewed)abstract
- Species are becoming extinct at unprecedented rates as a consequence of human activity. Hence it is important to understand the evolutionary dynamics of species with already small population sizes. Populus ilicifolia is a vulnerable poplar species that is isolated from other poplar species and is uniquely adapted to the Tropics. It has a very limited size, reproduces partly clonally and is therefore an excellent case study for conservation genomics. We present here the first annotated draft genome of P. ilicifolia, characterize genome-wide patterns of polymorphisms and compare those to other poplar species with larger natural ranges. P. ilicifolia experienced a more prolonged and severe decline of effective population size (Ne) and signs of genetic erosion than any other poplar species with which it was compared. At present, the species has the lowest genome-wide genetic diversity, the highest abundance of long runs of homozygosity, high inbreeding levels as well as a high overall accumulation of deleterious variants. However, more effective purging of severely deleterious variants and adaptation to the Tropics may have contributed to its survival. Hence, in spite of its limited genetic variation, it is certainly worth pursuing the conservation efforts of this unique species.
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| 2. |
- Zhang, Hongtao, et al.
(author)
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Enhancing fuel cell durability for fuel cell plug-in hybrid electric vehicles through strategic power management
- 2019
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In: Applied Energy. - : ELSEVIER SCI LTD. - 0306-2619 .- 1872-9118. ; 241, s. 483-490
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Journal article (peer-reviewed)abstract
- Fuel cell plug-in hybrid electric vehicles (FC-PHEVs) can have extended range while utilizing cheap grid electricity, but has poor durability of onboard fuel cells due to dynamic loading. In this study, fuel cell durability is enhanced significantly for a novel configuration of FC-PHEVs with three fuel cell stacks through strategic power management by making each fuel cell stack work only at a fixed operating point (i.e., constant output power) and by shortening its active time (operation) via on-off switching control. A hysteresis control strategy of power management is designed to make the active time evenly distributed over the three fuel cell stacks and to reduce the number of on-off switching. The results indicate that the durability of the onboard fuel cells can be increased 11.8, 4.8 and 6.9 times, respectively, for an urban, highway and a combined urban-highway driving cycle. This enhanced fuel cell durability is derived from the fact that the average power demand of real-time driving cycles is only a fraction of the maximum power that FC-PHEVs could provide, and substantially increased durability can be used to reduce the over-design, hence the cost, of fuel cells.
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| 3. |
- Zhang, Hongtao, et al.
(author)
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Power management optimization in plug-in hybrid electric vehicles subject to uncertain driving cycles
- 2020
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In: eTransporation. - : Elsevier BV. - 2590-1168. ; 3
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Journal article (peer-reviewed)abstract
- Optimization of power management in plug-in hybrid electric vehicles (PHEVs) with dual-power-source plays a critical role in achieving higher fuel economy and less pollutant emissions. In this study, power management and optimal control strategies in PHEVs have been investigated subject to uncertain driving cycles of individual drivers for particular trips. First, a stochastic driving cycle is constructed to more accurately model the dynamic characteristics of the uncertain driving cycles, derived from the historic record of individual drivers. Finite-horizon stochastic dynamic programming is adapted to globally optimize the vehicle performance in stochastic sense. Simulation results show that the proposed strategy significantly improves fuel economy, indicating the present optimization approach is very effective in exploring the potential of the hybridization of power train. A higher discretization of (that is, with smaller step sizes in) vehicle dynamics state variables (vehicle velocity, power demand and battery state of charge) has a positive impact on the fuel economy while the limitation of driving operability actually degrades the fuel economy. The commuting time with doubly truncated normal distribution slightly enhances the fuel economy in comparison with uniform distribution. In addition, there exists a tradeoff between the fuel economy and the pollutant emissions. These results could be utilized as a guideline for the design of PHEVs with different objectives.
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