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961.
962.
Intra-Urban Human Mobility and Activity Transition: Evidence from Social Media Check-In Data 总被引:2,自引:0,他引:2
Most existing human mobility literature focuses on exterior characteristics of movements but neglects activities, the driving force that underlies human movements. In this research, we combine activity-based analysis with a movement-based approach to model the intra-urban human mobility observed from about 15 million check-in records during a yearlong period in Shanghai, China. The proposed model is activity-based and includes two parts: the transition of travel demands during a specific time period and the movement between locations. For the first part, we find the transition probability between activities varies over time, and then we construct a temporal transition probability matrix to represent the transition probability of travel demands during a time interval. For the second part, we suggest that the travel demands can be divided into two classes, locationally mandatory activity (LMA) and locationally stochastic activity (LSA), according to whether the demand is associated with fixed location or not. By judging the combination of predecessor activity type and successor activity type we determine three trip patterns, each associated with a different decay parameter. To validate the model, we adopt the mechanism of an agent-based model and compare the simulated results with the observed pattern from the displacement distance distribution, the spatio-temporal distribution of activities, and the temporal distribution of travel demand transitions. The results show that the simulated patterns fit the observed data well, indicating that these findings open new directions for combining activity-based analysis with a movement-based approach using social media check-in data. 相似文献
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966.
Ronghai He X. Philip Ye Burton C. English Justinus A. Satrio 《Bioresource technology》2009,100(21):5305-5311
The poor and inconsistent physicochemical properties of bio-oil are inhibiting its industrialized production. We investigated the variability in properties of switchgrass bio-oil produced at three pyrolysis temperatures (T = 450, 500, and 550 °C) and three feedstock moisture contents (MC = 5%, 10%, and 15%) in a 3 × 3 factorial experiment in order to exploit opportunities to improve bio-oil properties through optimization of pyrolysis parameters. Results showed that even with the single type of feedstock and pyrolysis system, the two main factors and their interaction caused large variations in bio-oil yield and most of the measured physicochemical properties. Following improvements of bio-oil properties could be individually achieved by selecting an optimal pyrolysis condition (shown in parenthesis) comparing with the worst case: increase of bio-oil yield by more than twofold (MC = 10%, T = 450 °C), increase of pH by 20.4% from 2.74 to 3.3 (MC = 10%, T = 550 °C), increase of higher heating value by 18.1% from 16.6 to 19.6 MJ/kg (MC = 10%, T = 450 °C), decrease of density by 5.9% from 1.18 to 1.11 g/cm3 (MC = 5%, T = 550 °C), decrease of water content by 36% from 31.4 to 20.1 wt.% (MC = 5%, T = 450 °C), decrease of viscosity by 40% from 28.2 to 17 centistokes (MC = 5%, T = 550 °C), decrease of solid content by 57% from 2.86 to 1.23 wt.% (MC = 15%, T = 550 °C), and decrease of ash content by 41.9% from 0.62 to 0.36 wt.% (MC = 15%, T = 550 °C). There is no single, clear-cut optimal condition that can satisfy the criteria for a bio-oil product with all the desired properties. Trade-offs should be balanced according to the usage of the end-products. 相似文献
967.
This study involved the use of terrestrial plant extracts as substitutes for toxic chemicals to control the major fouling organisms of mangroves, the barnacles. In terms of the solvents used to obtain the plant crude extracts, ethyl acetate was best, ethyl alcohol next and pure water worst, except in the case of Allium cepa (AC), where pure water was better than ethyl alcohol. For different plants, different solvents resulted in different poisonous effects, and plants belonging to different classes showed different levels of activities. In particular, using ethyl acetate crude extracts, Allium sativum (AS), AC and Capsicum annuum (CA) caused massive death of barnacle larvae at a low concentration in the shortest time. The less poisonous organic solvents were able to extract more active materials, and this was advantageous in enhancing the effect. For pure water crude extracts, AC and Zingiber officinale were best, but for 95% ethyl alcohol crude extracts, AS and AC were best. For ethyl acetate crude extracts, the effects of AS, AC and CA were better. Different solvent extracts of AC with 12 h of exposure all had LC50 values <100 mg/L. The concentrations of the effective plant crude extracts used were close to, or even lower than, those used for pesticides referred to in the literature. 相似文献
968.
Lithium Batteries: Highly Nitridated Graphene–Li2S Cathodes with Stable Modulated Cycles (Adv. Energy Mater. 23/2015)
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969.
Drastic Layer‐Number‐Dependent Activity Enhancement in Photocatalytic H2 Evolution over nMoS2/CdS (n ≥ 1) Under Visible Light
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Kun Chang Mu Li Tao Wang Shuxin Ouyang Peng Li Lequan Liu Jinhua Ye 《Liver Transplantation》2015,5(10)
Exploiting noble‐metal‐free cocatalysts is of huge interest for photocatalytic water splitting using solar energy. As an efficient cocatalyst in photocatalysis, MoS2 is shown promise as a low‐cost alternative to Pt for hydrogen evolution. Here we report a systematical study on controlled synthesis of MoS2 with layer number ranging from ≈1 to 112 and their activities for photocatalytic H2 evolution over commercial CdS. A drastic increase in photocatalytic H2 evolution is observed with decreasing MoS2 layer number. Particularly for the single‐layer (SL) MoS2, the SL‐MoS2/CdS sample reaches a high H2 generation rate of ≈2.01 × 10?3m h?1 in Na2S–Na2SO3 solutions and ≈2.59 × 10?3m h?1 in lactic acid solutions, corresponding to an apparent quantum efficiency of 30.2% and 38.4% at 420 nm, respectively. In addition to the more exposed edges and unsaturated active S atoms, valence band–XPS and Mott–Schottky plots analysis indicate that the SL MoS2 has the more negative conduction band energy level than the H+/H2 potential, facilitating the hydrogen reduction. 相似文献
970.
Hanjie?Li Chenlin?Ye Ke?Liu Hanqi?Gu Weitao?Du Jie?BaoEmail author 《Bioprocess and biosystems engineering》2015,38(1):149-154
Particle size of lignocellulose materials is an important factor for enzymatic hydrolysis efficiency. In this study, corn stover was milled and sieved into different size fractions from 1.42, 0.69, 0.34, to 0.21 mm, and the corresponding enzymatic hydrolysis yields were 24.69, 23.96, 25.34, and 26.97 %, respectively. The results indicate that the hydrolysis yield is approximately constant with changing corn stover particle sizes in the experimental range. The overall surface area and the inner pore size measurement show that the overall specific surface area was less than 2 % with the half reduction of particle size due to the greater inner pore surface area. The scanning electron microscope photographs gave direct evidence of the much greater inner pore surface area of corn stover particles. This result provided a reference when a proper size reduction of lignocellulose materials is considered in biorefining operations. 相似文献