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Why Cycling in 2007 Was Faster than Being Driven in 2017 in Tianjin 预览
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作者 John Zacharias Qiang Sheng 《交通与运输工程:英文版》 2019年第1期1-12,共12页
Changes in the road environment of Tianjin were intended to speed up the traffic system and shift bicyclists to the metro,bus and car.The metro system was greatly expanded,along with a modernized bus fleet.App-based t... Changes in the road environment of Tianjin were intended to speed up the traffic system and shift bicyclists to the metro,bus and car.The metro system was greatly expanded,along with a modernized bus fleet.App-based taxi services were also introduced.In 2007,travellers to the central area were intercepted to determine the starting point of their trip and their travel mode.The most time-efficient trips in 2007 were by bicycle(61%).These trips were re-enacted in 2017 using taxi and metro as it was no longer physically possible to replicate most of the original bicycle trips.Trips greater than 5 km in distance were somewhat faster by taxi than they were by bicycle,but overall,travel time by taxi was greater than by the bicycle for those same trips in 2007.A network analysis of road changes provides explanation why longer trips became more efficient while short trips became less efficient.Travel by metro alone was much longer than the other two methods,but the combination of app-based bicycles and metro would render this travel method the most efficient. 展开更多
关键词 TRANSPORT efficiency non-motorized TRANSPORT road infrastructure TAXI hailing service BICYCLE private car
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5G Flexible Optical Transport Networks with Large-Capacity, Low-Latency and High-Efficiency 预览
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作者 Yuefeng Ji Jiawei Zhang +1 位作者 Yuming Xiao Zhen Liu 《中国通信:英文版》 SCIE CSCD 2019年第5期19-32,共14页
The fifth generation(5G) of mobile communications are facing big challenges, due to the proliferation of diversified terminals and unprecedented services such as internet of things(IoT), high-definition videos, virtua... The fifth generation(5G) of mobile communications are facing big challenges, due to the proliferation of diversified terminals and unprecedented services such as internet of things(IoT), high-definition videos, virtual/augmented reality(VR/AR). To accommodate massive connections and astonish mobile traffic, an efficient 5G transport network is required. Optical transport network has been demonstrated to play an important role for carrying 5G radio signals. This paper focuses on the future challenges, recent studies and potential solutions for the 5G flexible optical transport networks with the performances on large-capacity, low-latency and high-efficiency. In addition, we discuss the technology development trends of the 5G transport networks in terms of the optical device, optical transport system, optical switching, and optical networking. Finally, we conclude the paper with the improvement of network intelligence enabled by these technologies to deterministic content delivery over 5G optical transport networks. 展开更多
关键词 5G OPTICAL TRANSPORT NETWORKS OPTICAL devices OPTICAL TRANSPORT system OPTICAL SWITCHING OPTICAL NETWORKING
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The surface current method in gray Dancoff factor calculation 预览
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作者 Omid Safarzadeh 《核技术:英文版》 SCIE CAS CSCD 2019年第6期28-34,共7页
The Dancoff correction is important in the calculation of the effective cross section of resonant isotopes in a heterogeneous system. Although the neutron current method is a simple and straightforward approach to est... The Dancoff correction is important in the calculation of the effective cross section of resonant isotopes in a heterogeneous system. Although the neutron current method is a simple and straightforward approach to estimate the Dancoff factor, its use is limited to the black Dancoff factor. In this paper, we expand the current method used to determine both the black and gray Dancoff factors. The method developed also relies on a neutron transport solver, where a fixed source on a fuel rod surface has an outward direction, a cosine distribution, and a constant shape. The detector is located on the surface of the rods to measure incoming and outgoing currents;therefore, there is no need to calculate the chord length, and the development, validation, and verification of the code can be omitted. The mathematical foundation of the suggested method is derived using the integral transport equation. The effects of the moderator and lattice configuration are followed by a sensitivity analysis of the Dancoff factor for several problems, including pressurized water reactor and cluster fuel assemblies. The maximum and average relative errors of the calculated results are approximately 0.3% and 0.05%, respectively. 展开更多
关键词 BLACK Dancoff GRAY Dancoff INTEGRAL TRANSPORT EQUATION Interface current TRANSPORT SOLVER
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Systematic calibration of drift diffusion model for InGaAs MOSFETs in quasi-ballistic regime
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作者 Shaoyan DI Lei SHEN +4 位作者 Pengying CHANG Kai ZHAO Tiao LU Gang DU Xiaoyan LIU 《中国科学:信息科学(英文版)》 SCIE EI CSCD 2019年第6期122-129,共8页
This paper proposes a systematic procedure to calibrate the parameters of the drift-diffusion(DD) model for a performance evaluation of InG aA s MOSFETs in the quasi-ballistic regime. The simulation results of a deter... This paper proposes a systematic procedure to calibrate the parameters of the drift-diffusion(DD) model for a performance evaluation of InG aA s MOSFETs in the quasi-ballistic regime. The simulation results of a deterministic multi-subband Boltzmann transport equation(BTE) solver serve as the standard.The DD model is calibrated both under low and high electric fields. The electrostatic characteristics, low field mobility model, and high field saturation model are calibrated in proper sequence, and a good agreement among the drive current, carrier distribution, and velocity distribution are achieved between the results of the calibrated DD model and the BTE solver. The proposed calibration procedure can also be employed in devices made of other materials. 展开更多
关键词 DRIFT-DIFFUSION model calibration BOLTZMANN TRANSPORT equation BTE BALLISTIC TRANSPORT high field In GaAs MOSFET
CO2 emission of urban passenger transportation in China from 2000 to 2014 预览
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作者 YUAN Rui-Qiang TAO Xin YANG Xiang-Long 《气候变化研究进展:英文版》 CSCD 2019年第1期59-67,共9页
This study reviewed the urban passenger transportation(UPT)development of seven typical cities in China from 2000 to 2014,estimated the UPT CO2emission,analyzed the structure,and discussed the main factors of UPT CO,e... This study reviewed the urban passenger transportation(UPT)development of seven typical cities in China from 2000 to 2014,estimated the UPT CO2emission,analyzed the structure,and discussed the main factors of UPT CO,emission.Results showed that increases of GDP,population,and UPT scale of the cities have speeded up.The most significant development of UPT is that the growth of private vehicles is greatly faster than that of public transportation.The total and per-capita UPT CO2 emissions both increased.The share of private vehicles emission to total UPT CO2emission has increased,with the share in range of 65%-88%in 2014,exponentially leading to the increases of total and per-capita UPT CO2 emission.Although UPT CO2 emission structure with more share of public transportation would slow down the UPT CO2emission increase,private vehicle CO2 emission is recognized as the dominated driving factor.Contributions of driving factors,such as GDP,population,private vehicle CO2 emissions,to UPT CO2 emission are different among the cities.Private vehicle CO2 emission.is the dominated factor for UPT CO2emission in Beijing and Taiyuan.Besides private vehicle CO2emission,GDP also plays an important role in UPT CO2emissions of Chengdu,Shanghai,Guangzhou,and Urumqi.Contributions of private vehicle CO2 emission and GDP to UPT CO2 emission are almost same in Xi'an. 展开更多
关键词 URBAN PASSENGER TRANSPORT CO2 EMISSIONS Low-carbon TRANSPORT China
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Tuning the electronic transport anisotropy in borophene via oxidation strategy
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作者 HE YuanYuan CHENG Na +2 位作者 CHEN Chao XIONG ShiYun ZHAO JianWei 《中国科学:技术科学英文版》 SCIE EI CAS CSCD 2019年第5期799-810,共12页
Monolayer borophene, a novel kind of two-dimensional(2D) crystal, has been receiving intensive attention owing to its atomic thickness and metallic characteristics. Rational tuning the anisotropic electronic transport... Monolayer borophene, a novel kind of two-dimensional(2D) crystal, has been receiving intensive attention owing to its atomic thickness and metallic characteristics. Rational tuning the anisotropic electronic transport properties is essential to the application of monolayer borophene in electronic and optoelectronic devices. Herein, we developed an oxidation strategy to tune the anisotropic transport properties of borophene by changing O-defect coverage, using density functional theory combined with the nonequilibrium Green’s function formalism. It was found that for monolayer borophene, the preferable current flowing direction between armchair and zigzag could be reversed by modulating the surface O-defect coverage between 0 and 100%. The tunable anisotropic transport properties of oxidized borophene could be attributed to the interplay among several factors, including the surface charge transfer between O-defects and borophene layer, the scattering effects related to the coverage and orientation of O-B-O interfaces, and the additional transport channels through O-defects. Our work unveils the great potential of oxidization strategy in tuning the anisotropic electronic transport properties of monolayer borophene and is of significance to its application in high-performance electronic and optoelectronic nanodevices. 展开更多
关键词 borophene MONOLAYER ANISOTROPIC TRANSPORT O-defect COVERAGE carrier scattering TRANSPORT channel
Investigation on two triphenylene based electron transport materials
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作者 Minghan Cai Chongguang Zhao +2 位作者 Dongdong Zhang Xiaozeng Song Lian Duan 《中国科学:化学英文版》 SCIE EI CAS CSCD 2019年第6期775-783,共9页
Promoting electron mobility is the key to designing high performance electron transport materials(ETMs). Formation of intermolecular interaction can be helpful to enhance their electron mobilities as a result of more ... Promoting electron mobility is the key to designing high performance electron transport materials(ETMs). Formation of intermolecular interaction can be helpful to enhance their electron mobilities as a result of more ordered molecular stacking.Here, to reveal the inherent influence of intermolecular π-π stacking on the electron mobilities, we designed two ETMs, namely,2,4-diphenyl-6-[3-(2-triphenylenyl)phenyl]-1,3,5-triazine(TPTRZ) and 2,4-diphenyl-6-[4′-(2-triphenylenyl)[1,1′-biphenyl]-3-yl]-1,3,5-triazine(TPPTRZ). Thermal, photophysical and electrochemical measurement results indicate they are good ETM candidates. Additionally, TPTRZ and TPPTRZ exhibit high electron mobilities of 3.60×10-5 and 3.58×10-5 cm2V-1 s-1, respectively, at an electric field of 7×105 V cm-1. By taking X-ray single crystal structure, theoretical calculation and time of flight(TOF) results into consideration, it is revealed that strong intermolecular π-π stacking induced by planar triphenylene and triphenyltriazine units renders TPTRZ and TPPTRZ small energetic and positional disorder parameters, and results in their high electron mobilities thereby. By further enhancing intermolecular π-π stacking, ETMs with even higher electron mobilities can thus be anticipated. 展开更多
关键词 organic LIGHT-EMITTING diode ELECTRON transport material ELECTRON mobility π-π STACKING INTERMOLECULAR interaction
硫磺和放线菌强化植物修复土壤镉污染 预览
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作者 张子杨 郭瞻宇 +3 位作者 管伟豆 郭堤 李荣华 张增强 《中国环境科学》 EI CAS CSCD 北大核心 2019年第5期2106-2114,共9页
为了强化耐受重金属镉(Cd)的植物包心芥菜对土壤中Cd污染的富集及转运效率,以包心芥菜为研究对象,向土壤中添加0.3%的硫磺和接种不同数量的放线菌Act12(0.5,1.0,1.5,2.0g/kg),通过盆栽实验,研究不同处理间根际土pH值的变化规律、包心芥... 为了强化耐受重金属镉(Cd)的植物包心芥菜对土壤中Cd污染的富集及转运效率,以包心芥菜为研究对象,向土壤中添加0.3%的硫磺和接种不同数量的放线菌Act12(0.5,1.0,1.5,2.0g/kg),通过盆栽实验,研究不同处理间根际土pH值的变化规律、包心芥菜地上和地下部分Cd的积累量、植物抗氧化酶系的变化以及根系活力.结果表明:添加0.3%硫磺和2.0g/kg放线菌Act12后,根际土pH值下降最大,相比对照下降了14.5%.而添加0.3%硫磺和1.5g/kg的放线菌Act12,包心芥菜地上部分Cd的含量最高,转运系数最大,相比对照,Cd含量提高了79%,并且植物地上部分的干重最大.添加放线菌Act12对植物的抗氧化系统有积极作用,CAT、POD、SOD含量均在0.3%硫磺和1.0g/kg放线菌Act12的添加组合下达到峰值,放线菌Act12还可提高植物的根系活力,降低丙二醛的含量.综上表明,添加硫磺和放线菌Act12均可强化包心芥菜吸收土壤中Cd的能力,其中0.3%硫磺和1.5g/kg放线菌Act12的添加组合强化效果最佳. 展开更多
关键词 放线菌Act12 硫磺 包心芥菜 抗氧化酶 转运 富集
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新型防跑车防护装置的应用 预览
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作者 贾青霄 刘磊 吴传伟 《煤矿现代化》 2019年第3期103-105,共3页
采区轨道上山大绞车自动控制挡车栏,是用在倾斜井巷提升系统中防止跑车的专用设备,它与带有深度指示器的斜巷提升绞车配套使用,可实现巷道全程挡车栏自动控制。该挡车栏具有系统简单、安全可靠等优点,能够有效防止斜巷跑车事故的发生。... 采区轨道上山大绞车自动控制挡车栏,是用在倾斜井巷提升系统中防止跑车的专用设备,它与带有深度指示器的斜巷提升绞车配套使用,可实现巷道全程挡车栏自动控制。该挡车栏具有系统简单、安全可靠等优点,能够有效防止斜巷跑车事故的发生。但当发生跑车事故时,挡车拦在常闭状态下将矿车挡住防止跑车事故扩大的同时,由于车辆与挡车栏硬性撞击,往往发生挡车栏损坏的现象。为减少对挡车栏的损伤,减少影响提升运输时间,工区管理人员及技术人员集思广益,对现有挡车栏进行改造,增加了全断面绳栏缓冲器。采取新型挡车栏后,当跑车事故发生时,能够在缓冲器0.3~10m范围内有效阻拦车辆,减轻了对挡车栏的损伤,避免了跑车事故扩大。 展开更多
关键词 挡车栏 运输 车辆 缓冲器
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基于微分平滑的四旋翼运输系统轨迹跟踪控制 预览
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作者 梁晓 胡欲立 《控制理论与应用》 EI CAS CSCD 北大核心 2019年第4期525-532,共8页
四旋翼系绳运输系统是一种具有8个自由度和4个控制输入的欠驱动、强耦合、多变量的非线性系统.为建立系统模型,将系统解耦为双质点系绳连接子系统和四旋翼姿态控制子系统,基于广义拉格朗日方程推导出系统的动力学模型.然后利用微分平滑... 四旋翼系绳运输系统是一种具有8个自由度和4个控制输入的欠驱动、强耦合、多变量的非线性系统.为建立系统模型,将系统解耦为双质点系绳连接子系统和四旋翼姿态控制子系统,基于广义拉格朗日方程推导出系统的动力学模型.然后利用微分平滑理论证明了系统是以载荷位置和四旋翼偏航角为平滑输出的微分平滑系统.进而在等式限制条件下对平滑输出轨迹进行规划,获得前馈开环控制律.为抑制系统扰动并使跟踪误差收敛于原点,利用微分平滑特性推导出动态内反馈控制器.仿真实验验证了所提方法的有效性. 展开更多
关键词 四旋翼 运输 控制 平滑 动态反馈
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Tidal Asymmetry Changes in a Shallow Mud Estuary by a Restoration Project 预览
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作者 LIANG Huidi KUANG Cuiping +3 位作者 GU Jie MA Yue CHEN Kuo LIU Xu 《中国海洋大学学报:英文版》 SCIE CAS CSCD 2019年第2期339-348,共10页
The tidal asymmetry-induced siltation below tidal barriers is a worldwide problem that restricts regional socio-economic and environmental development.The hydrodynamic processes of the small mud estuary also feature a... The tidal asymmetry-induced siltation below tidal barriers is a worldwide problem that restricts regional socio-economic and environmental development.The hydrodynamic processes of the small mud estuary also feature a high uncertainty after estuary restoration measures.In this study,a hydrodynamic model based on the MIKE21 is used to quantify the responses of tidal asymmetry to a two-phase restoration project in Shuanglong Estuary,Bohai Bay,China.According to the numerical modeling results,the tidal flat removal in the upper estuary(first-phase restoration)induces the flood asymmetry switching to the ebb asymmetry in unrestored reach but enhances flood asymmetry in widening restored reach.Although the tidal asymmetry reverts to flood-dominated pattern after full restoration over the estuary,the imbalance between flood and ebb velocities is relieved.A possible net sediment transport pattern based on a comparison of dominant asymmetric current and actual sediment transport period shows net sediments in the upper estuary and inlet transport seaward and landward,respectively,in the first-phase restoration,whereas landward net sediment transport occurs in the whole estuary under the second-phase restoration scenario.Given these results,we assume that a switch from the flood-dominated estuary to ebb-dominated estuary can be caused by redesigning the cross-sectional profile.The quantitative comparison of Lagrangian residual currents also implies that a channel–shoal structure rather than a flat bathymetry can promote the mass transport.Therefore,reshaping the channel–tidal flat system in restoration projects can prevent the sedimentation of the estuary and improve the water environment. 展开更多
关键词 TIDAL asymmetry RESTORATION project MUD ESTUARY net SEDIMENT transport
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An interpretation of wave refraction and its influence on foreshore sediment distribution 预览
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作者 Vincent Jayaraj Joevivek Nainarpandian Chandrasekar +2 位作者 Ramakrishnan Jayangondaperumal Vikram Chandra Thakur Krishnan Shree Purniema 《海洋学报:英文版》 SCIE CAS CSCD 2019年第5期151-160,共10页
To analyze the grain size and depositional environment of the foreshore sediments,a study was undertaken on wave refraction along the wide sandy beaches of central Tamil Nadu coast.The nearshore waves approach the coa... To analyze the grain size and depositional environment of the foreshore sediments,a study was undertaken on wave refraction along the wide sandy beaches of central Tamil Nadu coast.The nearshore waves approach the coast at 45°during the northeast(NE)monsoon,at 135°during the southwest(SW)monsoon and at 90°during the non-monsoon or fair-weather period with a predominant wave period of 8 and 10 s.A computer based wave refraction pattern is constructed to evaluate the trajectories of shoreward propagating waves along the coast in different seasons.The convergent wave rays during NE monsoon,leads to high energy wave condition which conveys a continuous erosion at foreshore region while divergent and inept condition of rays during the SW and non-monsoon,leads to moderate and less energy waves that clearly demarcates the rebuilt beach sediments through littoral sediment transport.The role of wave refraction in foreshore deposits was understood by grain size and depositional environment analysis.The presence of fine grains with the mixed population,during the NE monsoon reveals that the high energy wave condition and sediments were derived from beach and river environment.Conversely,the presence of medium grains with uniform population,during SW and non-monsoon attested less turbulence and sediments were derived from prolong propagation of onshore-offshore wave process.These upshots are apparently correlated with the in situ beach condition.On the whole,from this study it is understood that beaches underwent erosion during the NE monsoon and restored its original condition during the SW and non-monsoon seasons that exposed the stability of the beach and nearshore condition. 展开更多
关键词 foreshore GRAIN size wave REFRACTION SEDIMENT transport BEACH INDIA
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亚投行交通运输行业战略浅析
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作者 孙宇宁 刘春卉 《一带一路报道》 2019年第2期104-107,共4页
亚洲基础设施投资银行于2018年10月发布了《交通运输行业战略》,将指导该行在亚洲乃至世界交通运输领域基础设施的投资。该战略概述了亚投行近几年内的目标,即为促进亚洲贸易和经济增长的可持续和一体化运输系统提供融资。亚投行希望为... 亚洲基础设施投资银行于2018年10月发布了《交通运输行业战略》,将指导该行在亚洲乃至世界交通运输领域基础设施的投资。该战略概述了亚投行近几年内的目标,即为促进亚洲贸易和经济增长的可持续和一体化运输系统提供融资。亚投行希望为具有财务回报和更广泛经济影响的项目提供融资。优先发展的项目有主干线连接、跨境互联互通、交通一体化项目和现有交通基础设施改造升级。 展开更多
关键词 亚投行 交通运输 投资 融资
Highly stable carbon-based perovskite solar cell with a record efficiency of over 18% via hole transport engineering
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作者 Qian-Qian Chu Bin Ding +8 位作者 Jun Peng Heping Shen Xiaolei Li Yan Liu Cheng-Xin Li Chang-Jiu Li Guan-Jun Yang Thomas P. White Kylie R. Catchpole 《材料科学技术学报:英文版》 SCIE EI CAS CSCD 2019年第6期987-993,共7页
Carbon-based perovskite solar cells show great potential owing to their low-cost production and superior stability in air, compared to their counterparts using metal contacts. The photovoltaic performance of carbon-ba... Carbon-based perovskite solar cells show great potential owing to their low-cost production and superior stability in air, compared to their counterparts using metal contacts. The photovoltaic performance of carbon-based PSCs, however, has been progressing slowly in spite of an impressive efficiency when they were first reported. One of the major obstacles is that the hole transport materials developed for stateof-the-art Au-based PSCs are not suitable for carbon-based PSCs. Here, we develop a low-temperature,solution-processed Poly(3-hexylthiophene-2,5-diyl)(P3 HT)/graphene composite hole transport layer(HTL), that is compatible with paintable carbon-electrodes to produce state-of-the-art perovskite devices. Space-charge-limited-current measurements reveal that the as-prepared P3 HT/graphene composite exhibits outstanding charge mobility and thermal tolerance, with hole mobility increasing from8.3 × 10^-3 cm^2 V-1 s-1(as-deposited) to 1.2 × 10^-2 cm2 V^-1 s^-1(after annealing at 100°C)-two orders of magnitude larger than pure P3 HT. The improved charge transport and extraction provided by the composite HTL provides a significant efficiency improvement compared to cells with a pure P3 HT HTL. As a result, we report carbon-based solar cells with a record efficiency of 17.8%(certified by Newport);and the first perovskite cells to be certified under the stabilized testing protocol. The outstanding device stability is demonstrated by only 3% drop after storage in ambient conditions(humidity: ca. 50%) for 1680 h(nonencapsulated), and retention of ca. 89% of their original output under continuous 1-Sun illumination at room-temperature for 600 h(encapsulated) in a nitrogen environment. 展开更多
关键词 Planar carbon-based PEROVSKITE solar cells Hole transport ENGINEERING RECORDED EFFICIENCY EXCELLENT moisture and light stability
Generalized algorithms for particle motion and collision with streambeds 预览
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作者 Patricio A.Moreno-Casas Fabian A. Bombardelli Juan Pablo Toro 《国际泥沙研究:英文版》 SCIE 2019年第4期295-306,共12页
Recent theoretical and numerical models for the motion of saltating particles close to stream beds are constituted of three sub-models: a) a set of equations describing the particle “free flight”, b) a sub-model to ... Recent theoretical and numerical models for the motion of saltating particles close to stream beds are constituted of three sub-models: a) a set of equations describing the particle “free flight”, b) a sub-model to calculate the post-collision particle velocity, and c) a mathematical representation of the bed roughness. In this paper, a comprehensive three-dimensional (3-D), theoretical/numerical model for bedload motion at large Reynolds numbers is presented. By using geometric considerations and stochastic parameters to characterize collisions with the wall, five new sub-models for representation of bed roughness are, for the first time to the best of our knowledge, proposed and implemented. The emphasis of this paper is on the particle model, for which Basset, Magnus, drag, submerged weight, virtual mass, and lift forces are included. For the range of particle sizes (sands) analyzed herein, it is found that the stream-wise contribution of the Basset force, compared to other forces, may be as large as 60%. Whereas in the wall-normal direction, the Basset force is equally important as the drag force, and it is exceeded only by the submerged weight. It is also found that the best agreement between numerical and experimental results in terms of jump length, jump height, and stream-wise particle velocity is achieved for restitution and friction coefficients of 0.65 and 0.1, respectively. Important conclusions are obtained regarding the lack of realistic prediction with available “roughness” models with small ranges of angles. 展开更多
关键词 Particlesaltation PARTICLE COLLISION PARTICLE ROTATION Bed-load TRANSPORT Basset FORCE
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Materials and structures for the electron transport layer of efficient and stable perovskite solar cells
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作者 Shizhao Zheng Gaopeng Wang +3 位作者 Tongfa Liu Lingyun Lou Shuang Xiao Shihe Yang 《中国科学:化学英文版》 SCIE EI CAS CSCD 2019年第7期800-809,共10页
The electron transport layer plays a vital function in extracting and transporting photogenerated electrons, modifying the interface, aligning the interfacial energy level and minimizing the charge recombination in pe... The electron transport layer plays a vital function in extracting and transporting photogenerated electrons, modifying the interface, aligning the interfacial energy level and minimizing the charge recombination in perovskite solar cells. This review summarizes the recent research progress on electron transport materials of metal oxides, organic molecules and multilayers. The doped metal oxides as electron transport materials in regular perovskite solar cells show improved device performance relative to their non-doped counterpart due to enhanced electron mobility and energy level alignment. The non-fullerene organic electron transport materials with better electron mobility and tunable energy level alignment need to be further designed and developed despite their advantages of mechanical flexibility and wide range tunability. The multilayer electron transport materials are suggested to be an important direction of research for efficient and stable perovskite solar cells because of their favorable synergistic interaction. 展开更多
关键词 PEROVSKITE solar cells electron transport layer metal OXIDE organic MOLECULES MULTILAYER
种植油麦菜评价多环芳烃污染土壤的农用风险
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作者 焦海华 郭佳佳 +3 位作者 张婧旻 张晓霞 茹文明 白志辉 《环境科学》 EI CAS CSCD 北大核心 2019年第5期2460-2470,共11页
污染土壤引起的农产品安全问题已不容忽视.为了探讨多环芳烃(polycyclic aromatic hydrocarbons,PAHs)污染土壤农用的安全性,本文通过盆栽实验方法,以某焦化企业周边长期受PAHs污染的农田土壤为研究对象,以广泛种植的油麦菜(Lactuca sat... 污染土壤引起的农产品安全问题已不容忽视.为了探讨多环芳烃(polycyclic aromatic hydrocarbons,PAHs)污染土壤农用的安全性,本文通过盆栽实验方法,以某焦化企业周边长期受PAHs污染的农田土壤为研究对象,以广泛种植的油麦菜(Lactuca sativa L.)为农产品代表,利用超声振荡提取和气相色谱-质谱联用仪(GC-MS)分析方法,解析样品中优先控制的16种PAHs的含量,揭示土壤-油麦菜体系中PAHs的迁移转化与富集特征,评估其潜在风险.结果表明,油麦菜地上部分(YS)PAHs的含量(Σ16PAHs)大于地下部分(GS),YS中3~5环PAHs相对含量高,GS中4~6环PAHs含量高. YS对不同PAHs的富集系数均大于GS,YS中蒽(Ant)的富集系数最大(2. 41),荧蒽(Fla)最小(0. 458),GS中苯并[a]芘(Bap)最大(0. 862),Fla最小(0. 130). 16种PAHs从GS到YS的转运系数均大于1. 00.关联性分析表明GS与初始土壤(SS) PAHs拟合优度中等(R~2=0. 71),YS与SS的PAHs拟合优度最大(R~2=1. 0),YS和GS的PAHs拟合优度最小(R~2=0. 39). YS和GS的健康风险值分别是国家食品标准Bap最大风险控制值的11. 8和12. 7倍.表明油麦菜食用的潜在风险较高,焦化企业周边污染土壤农用的安全问题不容忽视. 展开更多
关键词 多环芳烃(PAHs) 油麦菜 富集 迁移转化 污染土壤
Porosity and permeability variations of a dam curtain during dissolution 预览
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作者 Ji-xiang Huo Fu-heng Ma Xiao-lei Ji 《水科学与水工程:英文版》 EI CAS CSCD 2019年第2期155-161,共7页
During reservoir operation,the erosion effects of groundwater change the porosity and permeability of the dam curtain,causing changes to the seepage field.To understand where the changes take place and to what degree ... During reservoir operation,the erosion effects of groundwater change the porosity and permeability of the dam curtain,causing changes to the seepage field.To understand where the changes take place and to what degree the porosity and permeability change,a multi-field coupling model was built and solved.The model takes into account seepage,solution concentration,and solid structure.The model was validated using uplift pressure monitoring data.Then,the variations in curtain porosity,seepage flow,and loss quantity of Ca(OH)2 were calculated.The key time nodes were obtained through curve fitting of the variation of seepage flow with the BiDoseResp function.The results showed that the model could reflect the attenuation trend of curtain performance well.The process and position of the erosion were not homogeneous.Although erosion mainly occurred at the top and bottom of the curtain,it was most developed at the top.The erosion effects developed slowly during the early stage,much fast during the middle and late stages,and culminated in complete dissolution.The model results and the daily monitoring data can provide a scientific basis for the safe operation and management of reservoirs. 展开更多
关键词 DAM CURTAIN Permeability Multi-field coupling model POROSITY Erosion SOLUTE transport SEEPAGE flow
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河南省三次重污染过程的对比分析 预览
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作者 董贞花 齐伊玲 孔海江 《气象与环境学报》 2019年第1期18-25,共8页
利用气象观测资料、EC-Interim再分析资料、L波段雷达的探空资料以及空气污染资料,对比分析了河南省2015年11月27日至12月25日的3次重污染过程。首先从范围、时间、强度、首要污染物等方面对比分析这3次过程的污染特征。其次对比分析这... 利用气象观测资料、EC-Interim再分析资料、L波段雷达的探空资料以及空气污染资料,对比分析了河南省2015年11月27日至12月25日的3次重污染过程。首先从范围、时间、强度、首要污染物等方面对比分析这3次过程的污染特征。其次对比分析这三次过程的气象条件。结果表明:污染期间平直的环流、弱的气压场、高湿、小风、逆温均有利于重污染的产生;I和II污染最重日500hPa河南处在弱脊区,III处在槽后的西北气流中;偏北风有利于污染物由北向南的传输,造成大面积重污染且污染达到最重;三次重污染过程的结束均是由于西路冷空气入侵造成;风速、湿度、24h变温和24h变压与PM2.5有一定的超前滞后关系,其中超前4h风速、超前1h湿度、超前10h变温、超前19h变压和PM2.5浓度的相关性最好。边界层内,三次过程均存在不同程度的逆温,I过程大部分时间同时存在接地逆温和悬浮逆温;II和III整个过程几乎均有接地逆温存在,而大部分时间不存在悬浮逆温;湿度场的垂直方向上,I过程存在明显的上干下湿特征,而II和III过程不存在。II和III都是中西部污染最先清除、其次是北部、南阳和东部地区;而I过程北部最先清除。 展开更多
关键词 AQI 首要污染物 气象条件 相关 传输
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Flume experimental study on evolution of a mouth bar under interaction of floods and waves 预览
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作者 Li Yan Men-wu Wu +2 位作者 Ying Chen Yao Wu Tian-sheng Wu 《水科学与水工程:英文版》 EI CAS CSCD 2019年第2期162-168,共7页
Based on the characteristics of hydrodynamics and sediment transport in the bar area in the Modaomen Estuary,a flume experiment was performed to study the evolution of the longitudinal profile of the mouth bar.The mou... Based on the characteristics of hydrodynamics and sediment transport in the bar area in the Modaomen Estuary,a flume experiment was performed to study the evolution of the longitudinal profile of the mouth bar.The mouth bar evolution was investigated under the impacts of floods with different return periods as well as flood-wave interaction.The results showed that floods with different return periods had significant influences on the evolution of the river mouth bar.Particularly on the inner slope of the mouth bar,the sediment was substantially active and moveable.The inner slope and the bar crest tended to be remarkably scoured.The erosion was intensified with the increase of the magnitude of floods.Moreover,the bar crest moved seawards,while the elevation of the bar crest barely changed.Under the flood-wave interaction,a remarkable amount of erosion on the inner and outer slopes of the mouth bar was also found.The seaward displacement of the bar crest under the interaction of floods and waves was less than it was under only the impact of floods,while more deposition was found on the crest of the mouth bar in this case. 展开更多
关键词 MODAOMEN MOUTH bar Wave FLOOD FLUME experiment SEDIMENT transport
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