Dynamic Response of CFRP Reinforced Steel Beams Subjected to Impact Action Based on FBG Sensing Technology.

The in-situ health condition of carbon fiber reinforced polymer (CFRP) reinforced structures has become an important topic, which can reflect the structural performance of the retrofitted structures and judge the design theory. An optical fiber-based structural health monitoring technique is thus suggested. To check the effectiveness of the proposed method, experimental testing on smart CFRP reinforced steel beams under impact action has been performed, and the dynamic response of the structure has been measured by the packaged FBG sensors attached to the surface of the beam and the FBG sensors inserted in the CFRP plates. Time and frequency domain analysis has been conducted to check the structural feature of the structures and the performance of the installed sensors. Results indicate that the packaged Fiber Bragg Grating (FBG) sensors show better sensing performance than the bare FBG sensors in perceiving the impact response of the beam. The sensors embedded in the CFRP plate show good measurement accuracy in sensing the external excitation and can replace the surface-attached FBG sensors. The dynamic performance of the reinforced structures subjected to the impact action can be straightforwardly read from the signals of FBG sensors. The larger impact energies bring about stronger impact signals.

Comprehensive evaluation of loess collapsibility of oil and gas pipeline based on cloud theory.

The comprehensive evaluation of pipeline loess collapsibility risk is a necessary means to control the safety risks of pipelines in the collapsible loess section. It is also one of the critical scientific bases for risk prevention, control, and management. The comprehensive evaluation system of cloud theory consists of quantitative and qualitative indexes, and the evaluation system has the characteristics of randomness and fuzziness. In view of this problem, the standard qualitative and semi-quantitative evaluation methods have intense subjectivity in dealing with the uncertainty problems such as randomness and fuzziness of the system, the cloud theory, which can effectively reflect the randomness and fuzziness of things at the same time, is introduced. The state scale cloud and index importance weight cloud of pipeline loess collapse risk are constructed by the golden section method. The uncertainty cloud reasoning process of the quantitative indexes and the expert scoring method of the qualitative indexes are proposed. The comprehensive evaluation model of loess collapsibility risk of oil and gas pipeline is established, and the engineering example is analyzed. The complete evaluation results of 10 samples to be evaluated are consistent with the results of the semi-quantitative method and are compatible with the actual situation. The evaluation process softens the subjective division of index boundary, simplifies the preprocessing of index data, realizes the organic integration of quantitative and qualitative decisions, and improves the accuracy, rationality, and visualization of the results.

Individual factors influencing risk perceptions of hazardous chemicals in China.

In view of the public concern about the possible risks posed by hazardous chemicals in China, the study on risk perceptions offer an important opportunity to assess the public's awareness of the risks of hazardous chemicals as well as to predict the public behaviors. More specifically, this paper discusses the individual factors that affect risk perceptions and protective actions with 1700 questionnaires six cities of China. It was found upon statistical analysis that only gender has a significant impact on risk perceptions of all demographic indicators; what is more, men have a higher level of risk perceptions than women. Upon further analysis, four factors are identified and analyzed which are thought to affect risk perceptions and protective actions. Furthermore, the logical relationships among various elements were analyzed with SEM model. Results: first, one psychological factor (responsibility) and two ability factors (knowledge, skills) can make positive effects on risk perceptions; second, one psychological factor (trust) exerts a negative effect on risk perceptions; third, while psychological factors do make positive effects on protective actions, no significant correlation is found between the ability factors and protective actions. Then it can be deduced that it is beneficial to build a trusting relationship between the public and the government as well as to strengthen the public's sense of responsibility.

The Impact of Social Media on Risk Communication of Disasters-A Comparative Study Based on Sina Weibo Blogs Related to Tianjin Explosion and Typhoon Pigeon.

Social media has brought opportunities and challenges to risk communication of disasters by undermining the monopoly of traditional news media. This paper took blogs about Tianjin Explosion and Typhoon Pigeon posted through Sina Weibo as empirical objects. Moreover, the paper used the analytical method of social network to conduct a comparative study on the network structures of information disseminated among different types of disasters, with the goal of uncovering the impact of social media on different types of risk communication of disasters. The result shows a different impact of the risk communication on the two types of disasters. While the role of social media for the risk communication of natural disasters is mainly to influence information dissemination, the roles of social media for the risk communication of man-made disasters are to transmit information as well as to communicate emotions. The differences seen within the structure of social media networks are causes differences in functions. Specifically, the structure for the social media communication network on man-made disasters takes on a "core - periphery structure" which is endowed with both information communication and emotional communication functions. Also, the role of the opinion leaders for the subnet is found to be significant while the communication within small groups is kept pretty active; additionally, the slow speed of information transmission of the network could result in easily distorted information. On top of that, the network is characterized with intense vulnerability to the attacks on core nodes. In contrast, the social media network for natural disaster risk communication is not seen with an obvious "peripheral-core" structure which is a relatively pure information transmission network with relatively equal principal status. In other words, the entire network is found with stronger connectivity and relatively faster information transmission speed. Furthermore, the nodes inside the network are found to have weaker control over information transmission. In sum, the research results are helpful in improving the risk communication theory based on social relations, optimizing the communication structure of disaster information so as to change the effect of risk communication.

The Influence of Social Capital on Protective Action Perceptions Towards Hazardous Chemicals.

The stigmatized character of hazardous chemicals has caused individuals in hazards to take excessive protective actions. Here, social capital is introduced to discuss its influence on the protective action decision model (PADM), considering this variable has a relatively high individual trust level in regards to information on hazardous chemicals. A model was constructed by taking protective action perceptions as the dependent variable, social capital as the independent variable, the pre-decision process as the mediating variable, and socioeconomic status as the moderating variables. Data were collected with a neighborhood sampling method, and a total of 457 questionnaires were obtained from neighboring residents near a large cold ammonia storage house in Haidian District, Beijing. Results: While the family and friendship networks produced a larger positive influence, the kinship network produced a smaller positive influence; furthermore, the influence of social capital must be brought through the pre-decision process; finally, socioeconomic status has a directional moderation on the friendship network, an enhancing moderation on the kinship network, and a weakening moderation on the family network.

Experimental Investigation of the Compactability and Cracking Behavior of Polyacrylamide-Treated Saline Soil in Gansu Province, China.

Polyacrylamide (PAM) is a water-soluble polymer with the ability to enhance a soil's stability. PAM is currently being used to prevent irrigation-induced erosion and enhance the infiltration in farmland soil. To improve the compaction properties of the saline-soil-based filling material that is used in highway subgrade and the cracking resistance capacity of a saline soil's crust, the consistency limits, compactability, microstructure, and cracking morphology of untreated and PAM-treated saline soil were investigated. The saline soils were sampled from the soil crust and a depth of 2.0⁻3.0 m in Gansu Province, China. Two PAM concentrations (0.1% and 0.5% in mass ratio) were selected. The liquid limits and plastic limits of the saline soil samples from the surface (0⁻0.05 m) and a depth of 2.0⁻3.0 m noticeably increased as PAM concentration increased. The maximum dry densities decreased as PAM concentration and plasticity increased, and the optimum water contents of the two saline soil types did not significantly change. These results suggest that a higher shearing resistance between particles partially prevented compression from occurring during compaction. Mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM) test results showed that the PAM agent dispersed the bulky pellets, and the soil's structure was formed by flaky and acicular platelets that filled the micropores. A quantitative analysis of crack patterns showed that the cross-points of the crack network and the crack length decreased as the PAM concentration increased. These results indicate that an increase in PAM reduces the shrinkage strain and the flaws or pores within saline soils. Therefore, PAM's stabilizing effect on saline soil under a wetting⁻drying cycle was proven.

Compacted sewage sludge as a barrier for tailings: the heavy metal speciation and total organic carbon content in the compacted sludge specimen.

Acid mine drainage (AMD) was the main environmental problem facing the mining industry. For AMD had high heavy metals content and low pH, the compacted sewage sludge might be a barrier for tailings whose oxidation and weathering produced AMD, with its own carbon source, microorganism reduction ability and impermeability. To study the heavy metals environmental risk, under the simulate AMD, the deionized water (DW), and the pH 2.1 sulfuric acid water (SA) seepage conditions, respectively, the changes of the chemical speciation of heavy metals Cd, Cu, Fe, Ni, Zn and total organic carbon (TOC) content in the compacted sewage sludge were assessed in the different periods. The results indicated according to the distribution of heavy metals, the potential mobility was for Cd: 6.08 under AMD, 7.48 under SA, ∞ under DW; for Cu: 0.08 under AMD, 0.17 under SA, 0.59 under DW; for Fe: 0.15 under AMD, 0.22 under SA, 0.22 under DW; for Ni: 2.60 under AMD, 1.69 under SA, 1.67 under DW; and for Zn: 0.15 under AMD, 0.23 under SA and 0.21 under DW at the second checking time. TOC content firstly decreased from 67.62±0% to 66.29±0.35%, then increased to 67.74±0.65% under the AMD seepage while TOC decreased to 63.30±0.53%, then to 61.33±0.37% under the DW seepage, decreased to 63.86±0.41%, then to 63.28±0.49% under SA seepage. That indicated under the AMD seepage, the suitable microorganisms communities in the compacted sewage sludge were activated. And the heavy metals environmental risk of compacted sewage sludge was lower with AMD condition than with other two. So the compacted sewage sludge as a barrier for tailings was feasible as the aspect of environmental risk assessment.

Laboratory determination of migration of Eu(III) in compacted bentonite-sand mixtures as buffer/backfill material for high-level waste disposal.

For the safety assessment of geological disposal of high-level radioactive waste (HLW), the migration of Eu(III) through compacted bentonite-sand mixtures was measured under expected repository conditions. Under the evaluated conditions, advection and dispersion is the dominant migration mechanism. The role of sorption on the retardation of migration was also evaluated. The hydraulic conductivities of compacted bentonite-sand mixtures were K=2.07×10(-10)-5.23×10(-10)cm/s, The sorption and diffusion of Eu(III) were examined using a flexible wall permeameter for a solute concentration of 2.0×10(-5)mol/l. The effective diffusion coefficients and apparent diffusion coefficients of Eu(III) in compacted bentonite-sand mixtures were in the range of 1.62×10(-12)-4.87×10(-12)m(2)/s, 1.44×10(-14)-9.41×10(-14)m(2)/s, respectively, which has a very important significance to forecast the relationship between migration length of Eu(III) in buffer/backfill material and time and provide a reference for the design of buffer/backfill material for HLW disposal in China.

[Feasibility of sewage sludge used as filling material in permeable reactive barrier].

Permeable reactive barriers (PRB) have been used widely as an alternative technique to treatment of acid mine drainage (AMD). Selection of the appropriate filling materials is the most important procedure to application of this treatment. Batch adsorption tests and bacteria culture batch tests were conducted to assess the possibility of sewage sludge served as filling material for PRB. Results from batch adsorption tests showed that the maximum adsorption capacities of the sewage sludge were 13.62 mg x g(-1) (Zn2+) and 15.60 mg x g(-1) (Cd2+). Bacteria culture batch tests indicated that SO4(2-) concentrations in reactors decreased from initial concentrations of 700 mg x L(-1) to below 300 mg x L(-1). Sulfate removal efficiency ranged from 60% to 70%. Fe and heavy metals, including Zn and Cd, were removed completely in two reactors. This study suggested that sewage sludge is a suitable filling material for PRB.

[Oxidation buffer capacity of sewage sludge barrier for immobilization of heavy metals].

Benefit from the microbial activities especially the anaerobic sulfate reduction processes, sewage sludge could be used as a barrier to immobilize the heavy metals leached from tailings. With respect to the redox reaction between sewage sludge and acid mine drainage (AMD), oxidation titration test was carried out to study the effect of oxidation buffer capacity (OBC) of sewage sludge on the immobilization of heavy metals. Test results showed that OBC of sludge suspensions was decreased slightly with the solid-liquid ratio of the suspensions, but increased with the anaerobic incubation time, and that more than 50% of OBC was contributed by the sludge existed in strongly-reduction conditions (Eh < or = - 150 mV). During oxidation titration test, Zn was released obviously when Eh > or = - 150 mV, while Cu and Pb released obviously when Eh > or = 150 mV. According to the test results, a mathematical model was established to predict the OBC consumption of the sludge barrier under AMD penetrating conditions. The simulation results showed that a sludge barrier with 2m thickness, even undergone 38 787-years oxidation by AMD under 10m water head, keep in a strongly-reduced condition and, therefore, promote an immobilization of heavy metals from AMD in the barrier.

[Acid buffer capacity of sewage sludge barrier for immobilization of heavy metals].

Employing the anaerobic activities of microorganisms, sewage sludge can be used as a barrier to immobilize the heavy metals leached from tailings. Due to the interactions between sewage sludge barrier and acid mine drainage (AMD), it is possible that the heavy metals that have been immobilized previously might be released out. The acid buffering capacity (ABC) of sewage sludge suspensions with various anaerobic incubation time and the effect of ABC on the mobility of heavy metals were investigated by acid titration tests. Test results showed that ABC of sewage sludge suspensions was increased with the solid-liquid ratio of the suspensions and the anaerobic incubation time, and that carbonate and organics play an important role in acid buffer of sewage sludge suspensions. During the acid titration test, Zn, Pb and Cu were released out obviously following the order of Zn > Cu > Pb as pH was decreased less than 6.2. A mathematical model was established to predict the ABC consumption of the sewage sludge barrier under AMD penetration condition. The simulation results showed that a sewage sludge barrier with 2.0 m thickness, even undergoing 666-years acidification by AMD under 10.0 m water head, can maintain a condition of pH > or = 6.2 and, therefore, keep immobilize the heavy metals of AMD in the barrier.