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This study presents a new type of bamboo scrimber beams that are strengthened by fiber-reinforced polymer (FRP) composite sheets embedded in the internal tensile region with an additional bamboo plate. To investigate the flexural performance of the bamboo scrimber beams, four-point bending tests were conducted to determine the failure modes, the load-displacement relationship, the load carrying capacity and the flexural rigidity of reinforced bamboo scrimber beams. The main parameters in the tests were the number of FRP layers and the type of FRP. The results indicated that the failure of the strengthened beams started with tensile fractures on the bottom bamboo plates, and no slipping was observed between the strengthening materials and the original bamboo beams prior to the rupturing of the bamboo plates. The flexural load-carrying capacity and the flexural rigidity of the strengthened beams effectively increased due to the FRP composite sheets and an additional bamboo plate. The strengthening method has a beneficial effect on promoting the compression behavior in the compression zone of the cross-sections of bamboo beams. Based on a simple stress-strain model of bamboo scrimber, a theoretical method for predicting the flexural load carrying capacity was developed. The predicted results are consistent with the test results. [ABSTRACT FROM AUTHOR]

• Bamboo scrimber were tested under cyclic compression loading. • Cyclic compressive behavior of bamboo scrimber was investigated for the first time. • Bamboo scrimber has prominent flexibility and recovery performance. • Cyclic stress-strain model is developed for predicting the entire cyclic stress-strain response. Bamboo has become a promising construction material for replacing nonrenewable and polluting materials due to its ecological characteristics, low carbon content, high axial strength, favorable flexibility, and associated energy savings. Although the excellent flexibility and recovery abilities of bamboo have been recognized, their quantitative description has not yet been established. To quantitatively describe the flexibility and recovery performance of bamboo, the compressive behavior of bamboo scrimber columns under cyclic compressive loading was investigated for the first time. The results illustrate that the failure modes of bamboo scrimber columns include buckling, shearing and splitting, and the residual plastic strain ratio of bamboo scrimber is far lower than that of concrete in a high strain range. A cyclic stress-strain model, including the envelope and the unloading and reloading segments of the cyclic stress-strain curve, was developed for predicting the entire cyclic stress-strain response of bamboo scrimber. The proposed model is able to accurately predict the entire cyclic stress-strain response of bamboo scrimber and provides a quantitative description of the flexibility and recovery abilities of bamboo, which can be used to simulate the seismic response of bamboo structures. [ABSTRACT FROM AUTHOR]

Although considerable efforts have been made in converting carbon dioxide to hydrocarbons via hydrogenation processes, precise control of C–C coupling towards heavy olefins remains a challenge. Here we report a carbon dioxide hydrogenation to olefin process that achieves 72% selectivity for alkenes and 50.3% selectivity for C4–18 alkenes, of which formation of linear α-olefins accounts for 80%. The process is catalyzed by carbon-supported iron, commonly used in C–C coupling reactions, with multiple alkali promoters extracted from corncob. The design is based on the synergistic catalysis of mineral elements in biomass enzyme on which carbon dioxide can be directly converted into carbohydrate. The mineral elements from corncob may promote the surface enrichment of potassium, suppressing the secondary hydrogenation of alkenes on active sites. Furthermore, carburization of iron species is enhanced to form more Fe5C2 species, promoting both the reverse water–gas shift reaction and subsequent C–C coupling. The conversion of carbon dioxide into valuable commodity chemicals is a promising approach to exploit anthropogenic emissions. Here, the authors use carbon-supported iron combined with alkali promoters derived from biomass to convert carbon dioxide directly to heavy linear terminal olefins. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Silicalite-1 based microcapsule catalysts were prepared with hydrothermal synthesis. • Silicalite-1 shell turned Fe/ZSM-5 core's surface hydrophilicity to hydrophobicity. • Hydrophobic nature of silicalie-1 layer decreased water-gas shift reaction's kinetics. • CO 2 selectivity was decreased by suppressing water-gas shift reaction activity. • Acidic ZSM-5 and silicalite-1 molecular sieving contributed in high gasoline selectivity. Abstract Zeolite supported Fischer-Tropsch (FT) catalysis has attracted extensive attentions in past few years. Capsule catalysts have unique characteristics of tuning product selectivity more precisely and enhancing stability of catalysts during reaction, which makes them to stand out of the crowed. Fe-based FT catalysts have been facing limitations for syngas conversion to hydrocarbons with their associated problems of high CO 2 selectivity and rapid catalyst deactivation. A series of ZSM-5 supported Fe-based microcapsule catalysts, composed of Fe/ZSM-5 core and silicalite-1 shell, was prepared and employed for direct synthesis of gasoline range hydrocarbons from syngas. Tuning silicalite-1 shell thickness significantly affected water-gas shift reaction with increasing hydrophobicity of catalyst surface, and greatly decreased CO 2 selectivity. The microcapsule catalysts significantly suppressed the CO 2 selectivity as compared with supported Fe-based catalyst. Moreover, all zeolite supported Fe-based catalysts, showed significantly high gasoline range hydrocarbons selectivity (about 60%). The proposed catalyst design suggests a promising approach to overcome high CO 2 selectivity challenge associated with Fe-based FT catalysts. [ABSTRACT FROM AUTHOR]

China’s fast economic growth contributes to the rapid development of its urbanization process, and also renders a series of industrial accidents, which often cause loss of life, damage to property and environment, thus requiring the associated risk analysis and safety control measures to be implemented in advance. However, incompleteness of historical failure data before the occurrence of accidents makes it difficult to use traditional risk analysis approaches such as probabilistic risk analysis in many cases. This paper aims to develop a new methodology capable of assessing regional industrial safety (RIS) in an uncertain environment. A hierarchical structure for modelling the risks influencing RIS is first constructed. The hybrid of evidential reasoning (ER) and Analytical Hierarchy Process (AHP) is then used to assess the risks in a complementary way, in which AHP is hired to evaluate the weight of each risk factor and ER is employed to synthesise the safety evaluations of the investigated region(s) against the risk factors from the bottom to the top level in the hierarchy. The successful application of the hybrid approach in a real case analysis of RIS in several major districts of Beijing (capital of China) demonstrates its feasibility as well as provides risk analysts and safety engineers with useful insights on effective solutions to comprehensive risk assessment of RIS in metropolitan cities. The contribution of this paper is made by the findings on the comparison of risk levels of RIS at different regions against various risk factors so that best practices from the good performer(s) can be used to improve the safety of the others. [ABSTRACT FROM AUTHOR]

There have generally been two kinds of approaches to the empirical study of human mobility. At the group level, some valuable information might be submerged in statistical noise, while due to the diversity of individual purpose and preference, there is still no general statistical regularity of human mobility at the individual level. In this paper, we considered group-level human mobility as the combination of several basic patterns and analyzed the collective mobility by category. Utilizing matrix factorization and correlation analysis, we extracted some of the stable/occasional components from the collective human mobility in the Beijing subway and found that the departure and arrival mobility patterns have different characteristics, both in time and space, under various conditions. We classified individual records into different patterns and analyzed the most likely trip distance by category. The proposed method can decompose stable/occasional mobility patterns from the collective mobility and identify passengers belonging to different patterns, helping us to better understand the origin of different mobility patterns and provide guidance for emergency management of large crowds. [ABSTRACT FROM AUTHOR]

We studied the distribution of entry time interval in Beijing subway traffic by analyzing the smart card transaction data, and then deduced the probability distribution function of entry time interval based on the Maximum Entropy Principle. Both theoretical derivation and data statistics indicated that the entry time interval obeys power-law distribution with an exponential cutoff. In addition, we pointed out the constraint conditions for the distribution form and discussed how the constraints affect the distribution function. It is speculated that for bursts and heavy tails in human dynamics, when the fitted power exponent is less than 1.0, it cannot be a pure power-law distribution, but with an exponential cutoff, which may be ignored in the previous studies. [ABSTRACT FROM AUTHOR]

Menezes and Barabasi have once developed a framework by mean–variance analysis to investigate the relationship between the average flux and fluctuations and found a scaling-law behavior in two distinct phase. By then most related researches dedicated to understanding the scaling laws through the internal/external forces of the system. However, as for subway system, the demand of transporting a large amount of passengers during peak hours is a necessity. Thus, alternating the phase or reducing the impact of external forces by cutting down the total passengers is completely unrealistic. The more operable approaches are specifically regulating the distribution of passenger flow in order to drive the system into a more stable phase. In this paper, we carried out the mean–variance analysis on subway traffic and dedicated to discover the effect of spatial–temporal distributions of passenger flow on the fluctuations in subway traffic. By analyzing the control properties of the transit networks constructed according to different passenger flow threshold , it is found that the control mode of transit networks might differ the phase change of fluctuations, which proposed a new perspective of controlling the fluctuations in subway traffic. • Transit network of metro system was constructed to character the spatial–temporal distribution of traffic. • Clear scaling-law can be observed between the mean and variance of passenger flow in the transit network. • The scale exponent vary within a day and are dominated by the traffic variation and the control mode of the transit networks. • Traffic restrictions should be given in priority to stations with large inbound and outbound traffic at morning (evening) peak hours. [ABSTRACT FROM AUTHOR]