摘要 :
In order to solve the problem of insufficient range caused by the excessive weight of the pure electric bus, a multi-objective genetic algorithm (GA) and radial basis function (RBF) model are combined in this paper to realize the ...
展开
In order to solve the problem of insufficient range caused by the excessive weight of the pure electric bus, a multi-objective genetic algorithm (GA) and radial basis function (RBF) model are combined in this paper to realize the lightweighting of steel and aluminum hybrid body of the pure electric bus. First, the upper and lower frames of the pure electric bus body are initially designed with aluminum alloy and steel materials respectively to meet the lightweight requirements. Second, a finite element (FE) model of the bus body is established, and the validity of the model is validated through physical tests. Then, the sensitivity analysis is performed to identify the relative importance of individual design parameters over the entire domain. The Hamosilei sampling method is selected for the design of the experiment (DOE) because users can specify the number of experiments and ensure that the set of random numbers is a good representative of real variability, and the RBF model is adopted to approximate the responses of objectives and constraints. Finally, the multi-objective optimization (MOO) method based on GA with RBF model is used to solve the optimization problem of the lightweight steel-aluminum hybrid bus body. The results show that compared with the traditional fully steel body, the use of the aluminum alloy lower-frame structure can reduce body mass by 38.4%, and the proposed optimization method can further reduce the mass of the steel-aluminum body to 4.28% without affecting the structural stiffness and strength performance of the body.
收起
摘要 :
We establish the link between energy use, air pollution, and public health impacts in Taiyuan for 2000, and for 2010 and 2015 under alternative scenarios. We find that in year 2000 more than 2200 excess deaths may have been caused...
展开
We establish the link between energy use, air pollution, and public health impacts in Taiyuan for 2000, and for 2010 and 2015 under alternative scenarios. We find that in year 2000 more than 2200 excess deaths may have been caused by paniculate matter (PM) pollution. Using alternative methods for monetization of health impacts the total health damage amounts to 0.8-1.7 billion Yuan, which is 2.4-4.9% of the city's GDP in 2000. Compared to the business-as-usual scenario, scenarios assuming extensive fuel switch in low-and-medium-stack pollution sources and extension of the district heating system could prevent 200-1100 PM_(10)-related premature deaths in 2010 and substantially reduce population morbidity. The actual PM pollution in 2007 was lower than modeled in these two scenarios. We also find that if air quality in urban Taiyuan were to reach the Chinese National Grade II Standard in 2015, the number of premature deaths would still be around 1330 and the economic cost about 1 -2% of the city's GDP in 2015. Our results imply that there are large health benefits to be gained by setting stricter standards for the future in China, and that targeting low-and-medium-stack source effectively reduces health damage.
收起
摘要 :
Facing the mounting pressure on energy security and increasing environmental concerns about air pollution and climate change, the Chinese government set a mandatory goal of 20% reduction of energy intensity in its 11th Five-Year P...
展开
Facing the mounting pressure on energy security and increasing environmental concerns about air pollution and climate change, the Chinese government set a mandatory goal of 20% reduction of energy intensity in its 11th Five-Year Plan period (FYP, 2006-2010). In this paper we use Shanxi province to illustrate how policies and measures are implemented in practice at a provincial level as a response to the National FYP issued by the central government. Local policies are described and their effects are analyzed. We compare reported energy saving achievements with our own estimates and conclude that the achievements in Shanxi probably have been substantial since the start of the 11th FYP period. The most important measures taken by provincial and local governments seem to be in the secondary sector, such as Top-200/Top-1000 program and phasing out outdated technologies. However, Shanxi has still a long way to go to achieve satisfactory energy use. Further improvement of energy intensity will require continuing efforts. Although many measures are necessary, improving the energy efficiency in heavy industries and reducing the dependence on these industries should be particularly effective.
收起
摘要 :
Monodisperse β-NaYF4:Yb,Tm nanocrystals (nanospheres and nanoplates) with a uniform size were successfully synthesized. By tuning the ratios of solvent, reaction temperature, and reaction time, we manipulated their phase, shape, ...
展开
Monodisperse β-NaYF4:Yb,Tm nanocrystals (nanospheres and nanoplates) with a uniform size were successfully synthesized. By tuning the ratios of solvent, reaction temperature, and reaction time, we manipulated their phase, shape, and size in the range of 3-400 nm. As a chelating agent and shape modifier, oleic acid (OA) was introduced into the reaction mixtures and played a key role in fine-tuning the nanocrystals. Possible mechanisms were proposed for forming the products with various architectures. Spectral analysis showed that the β-NaYF4:Yb,Tm nanocrystals were excellent materials for intense ultraviolet and blue upconversion luminescence. Here, we demonstrate that, under 980 nm excitation, the intense 5-photon upconversion fluorescence (290 nm and 345 nm) from the ~1I6 level of Tm~(3+) ions is much stronger than the 4-photon upconversion fluorescence (361 nm and 451 nm) from the ~1D2 level and the 3-photon upconversion fluorescence (474 nm) from the ~1G4 level. The analysis of the temporal evolution of UC luminescence suggests that long lifetimes benefit the intense ultraviolet upconversion luminescence.
收起
摘要 :
By using a novel and low-cost microwave method, three-dimensional SiC networks have been synthesized in large-scale. The composition and structural features of the product were characterized by X-ray diffraction, field emission sc...
展开
By using a novel and low-cost microwave method, three-dimensional SiC networks have been synthesized in large-scale. The composition and structural features of the product were characterized by X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. The results show that the SiC networks consist of nanocable X-junction and Y-junction. Some nanocables are composed of 3C-SiC multicore encapsulated in single amorphous SiO_2 shell. The SiC networks emitted stable violet-blue light around 380 nm under 325-nm excitation. Compared to the emission peak of the SiC networks after etched and the reported results of 3C-SiC nanowires, the emission peak of the SiC networks shows significant blueshift. The origin of the photoluminescence for the SiC networks could be due to two possible reasons: the central crystalline SiC nanowires and amorphous SiO_2 shell. A two-step growth mechanism of the SiC networks was proposed based on the experimental characterizations. The successful synthesis of SiC networks is an important step in the development of SiC-based electronic devices and circuits.
收起
摘要 :
Multiphoton upconversion (UC) emissions from the high-energy states (4 G 9/2, 4 G 7/2, 2 K 13/2, and 2 P 3/2) of Er3+ ions were observed under 980 nm excitation. These high-energy excited states were populated by a five-photon or ...
展开
Multiphoton upconversion (UC) emissions from the high-energy states (4 G 9/2, 4 G 7/2, 2 K 13/2, and 2 P 3/2) of Er3+ ions were observed under 980 nm excitation. These high-energy excited states were populated by a five-photon or a four-photon UC process conditionally, which depended on the near-infrared (NIR) pump density. Experiments exhibited that the power dependence originated from the varied populating routes of intermediated 4 S 3/2 and 4 F 9/2 of Er3+ under different NIR pump power. A mechanism of the power density-dependent multiphoton UC processes was proposed based on experimental data and analysis.
收起
摘要 :
Yb~(3+) , Er~(3+) , and Tm~(3+)-codoped Gd2O3 nanotubes were synthesized via a simple wet-chemical route at low temperature and ambient pressure followed by a subsequent heat treatment at 800 °C. X-Ray diffraction (XRD), field em...
展开
Yb~(3+) , Er~(3+) , and Tm~(3+)-codoped Gd2O3 nanotubes were synthesized via a simple wet-chemical route at low temperature and ambient pressure followed by a subsequent heat treatment at 800 °C. X-Ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), thermogravimetric analysis (TGA), upconversion (UC) emission spectra, and kinetic decay were used to characterize the samples. Bright white UC luminescence in the nanotubes was observed under diode laser excitation of 980 nm. The white light consists of the blue (~1G4 →~3H6 of Tm~(3+)), green (~2H_(11/12)/~4S_(3/2)→ ~4I_(15/2) of Er~(3+)), and red (~4F_(9/2)→ ~4I_(15/2) of Er~(3+)) UC emissions. As the excitation power density changed in the range of 20-200 W cm~(-2), the calculated CIE color coordinates shift only slightly and fall well within the white region. This material may be a potential candidate for applications of color displays, lighting and photonics.
收起
摘要 :
Silicon nanoholes (Si NHs) were synthesized by a simple metal-assisted chemical etching method. With different pre-etching time of Ag particles, Si NHs with different morphology and Si nanowires (NWs) were prepared. After tetramet...
展开
Silicon nanoholes (Si NHs) were synthesized by a simple metal-assisted chemical etching method. With different pre-etching time of Ag particles, Si NHs with different morphology and Si nanowires (NWs) were prepared. After tetramethyl ammonium hydroxide (TMAH) etching, the NH sample with preetching Ag particles for 20 min show average reflectance below 5% which is comparable to the reflectance of the NW sample. The minority carrier lifetime of this NH sample is 58.2 μs due to their low surface recombination, while the lifetime of the NWs is 38.0 ls under the same iodine–ethanol passivation.
收起
摘要 :
Under 1560nm excitation, ultraviolet (UV) upconversion (UC) emissions of Gd~3+ and Er~3+ ions were observed in p-NaYF_4:Yb~3+/Gd~3+/Er~3+ microcrystals, which were synthesized through a facile EDTA-assisted hydrothermal method. Ex...
展开
Under 1560nm excitation, ultraviolet (UV) upconversion (UC) emissions of Gd~3+ and Er~3+ ions were observed in p-NaYF_4:Yb~3+/Gd~3+/Er~3+ microcrystals, which were synthesized through a facile EDTA-assisted hydrothermal method. Experimental analysis exhibited that these UV emissions came from high-order UC processes. In the Yb~3+-Gd~3+-Er~3+ codoped system, ground state absorption (GSA) and excited state absorption (ESA) of Er-37,ESA of Gd~3+, energy transfers (ETs) from Yb~3+ to Er~3+ and from Er~3+ to Gd~3+ ions worked simultaneously in populating these high-energy states of Er~3+ and Gd~3+ ions.
收起
摘要 :
High-order ultraviolet (UV) upconversion (UC) emissions of Gd~(3+) and Er~(3+) ions were observed in NaYF4:Yb~(3+)/Gd~(3+)/Er~(3+) microcrystals under 980 nm excitation. These UC emissions came from six- and five-photon UC process...
展开
High-order ultraviolet (UV) upconversion (UC) emissions of Gd~(3+) and Er~(3+) ions were observed in NaYF4:Yb~(3+)/Gd~(3+)/Er~(3+) microcrystals under 980 nm excitation. These UC emissions came from six- and five-photon UC processes at low pump power range, which were confirmed by the pumping power dependences of UC fluorescence intensities. In these high-order UC processes, energy transfer (ET) processes of Er~(3+) - > Gd~(3+) played crucial roles in populating the excited states of Gd~(3+) ions. Experiments on concentration variation and dynamic analysis revealed the ET processes between Er~(3+) and Gd~(3+) in detail. Some of possible population routes for populating excited Gd~(3+) ions were proposed based on spectral and dynamic analysis.
收起
原文获取