Laboratory study on the mechanical behaviors of an anisotropic shale rock

Shale gas is becoming an important energy source worldwide. The geomechanical properties of shalerocks can have a major impact on the efficiency of shale gas exploration. This paper studied themineralogical and mechanical characteristics of a typical gas shale in Ohio, USA. Scanning electron microscope（SEM） with energy dispersive X-ray （EDX） analyses was employed to measure the microstructureand material composition of the shale rock. The anisotropic behaviors of shale rock, includingcompressive and tensile strengths, were experimentally measured. The characteristics of shale rock werealso studied by nondestructive wave speed measurements. The shale demonstrated strong anisotropicbehaviors with the tensile strengths perpendicular to the bedding plane around 300e360 times of thatparallel to bedding plane. Results of ultrasonic tests indicated that both compression and shear wavevelocities show strong anisotropic patterns. The compression wave speed was the smallest in the directionperpendicular to the bedding plane; while the shear wave speed was the smallest in the directionparallel to the bedding plane. The ratio of wave speed anisotropy is around 1.3e1.4 for compressionwave; the ratio of shear wave speed anisotropy is larger and more diverse compared with thecompression wave anisotropy. This might be related to the larger variability in the frictional adhesivestrength along bedding plane than the compressive adhesive strength. 2015 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.

Novel mechanical behavior of periodic structure with the pattern transformation

Abstract In periodic cellular structures, novel pattern transformations are triggered by a reversible elastic instability under the axial compression. Based on the deformation-triggered new pattern, periodic cellular structures can achieve special mechanical properties. In this paper, the designed architecture materials which include elastomer matrixes containing empty holes or filled holes with hydrogel material are modeled and simulated to investigate the mechanical property of the periodic materials. By analyzing the relationship between nominal stress and nominal strain of periodic material, and the corresponding deformed patterns, the influence of geometry and shapes of the holes on the mechanical property of architecture material is studied in more details. We hope this study can provide future perspectives for the deformation-triggered periodic structures.

The impact of China’s high-speed rail investment on regional economy and air pollution emissions

The high-speed rail(HSR)network in China has experienced rapid development since the 2000s.In 2016,the State Council of the People’s Republic of China issued a revised version of the“Mid-and Long-term Railway Network Plan”,detailing the expansion of the railway network and construction of an HSR system.In the future,the HSR construction efforts in China will further increase,which is considered to impact regional development and air pollutant emissions.Therefore,in this paper,we apply a transportation network-multiregional computable general equilibrium(CGE)model to estimate the dynamic effects of HSR projects on economic growth,regional disparities,and air pollutant emissions in China.The results indicate that HSR system improvement could generate a positive economic impact but could also increase emissions.The gross domestic product(GDP)growth per unit investment cost stimulated by HSR investment is found to be the largest in eastern China but the smallest in the northwest regions.Conversely,HSR investment in Northwest China contributes to a substantial reduction in regional disparities in terms of the GDP per capita.In regard to air pollution emissions,HSR construction in South-Central China results in the largest increase in CO_(2) and NO_(X) emissions,while for CO,SO_(2),and fine particulate matter(PM_(2.5))emissions,the largest increase occurs due to HSR construction in Northwest China.At the regional level,the provinces with large changes in accessibility also experience large changes in their air pollutant emissions.

Determination of N-nitrosodimethylamine in drinking water by UPLC-MS/MS

The method for detecting N-nitrosodimethylamine （NDMA） in drinking water using ultra performance liquid chromatography （UPLC） coupled with tandem mass spectrometry （MS/MS） was improved by optimizing the clean-up procedure to remove the matrix interference in pretreatment process, and was then applied to a survey of NDMA in both raw and finished water samples from five water treatment plants in South China. The NDMA concentrations ranged from 4.7 to 15.1 ng/L in raw water samples, and from 4.68 to 46.9 ng/L in finished water. The NDMA concentration in raw water was found to be related with nitrite concentration, and during the treatment, the NDMA concentration increased following ozonation but decreased after subsequent activated carbon treatment.

A looped heat-driven thermoacoustic refrigeration system with direct-coupling configuration for room temperature cooling

Heat-driven thermoacoustic refrigeration has drawn extensive concern in the past decades due to its advantages of high reliability and external heat-driven mechanism.In such a system,heat can be firstly converted into acoustic power and then the acoustical power drives a refrigerator to generate cooling effect without any moving mechanical components.So far,most of researches on heat-driven thermoacoustic refrigeration have focused on cryo- genic application,such as natural gas liquefaction [1,2].In addition, heat-driven thermoacoustic refrigeration also plays important roles in recovering waste heat and provides an environment- friendly alternative to the current abso'rption chiller especially in the small-scale power range [3-7].However,two main obstacles to use the thermoacoustic technology in practice are its relatively low cooling capacity and low cooling efficiency.Either the two-loop configuration proposed by Luo et al.[5]or the configuration of a one-unit refrigerator driven by a three-unit engine brought forward by Kees [6],they both suffer from phase-shifting tube and mismatch between the thermoacoustic engine (TAE)and thermoacoustic refrigerator (TAR).

Thermally controlled large deformation in temperaturesensitive hydrogels bilayers

The present work investigates the thermally controlled deformation characteristics in temperature-sensitive hydrogels bilayers.The free energy density for temperature-sensitive hydrogels is modified,upon which the finite element model is developed and implemented through user-defined material subroutine UHYPER in the commercial software ABAQUS.The modified UHYPER implementation allows for more vividly depicting the continuous deformation in phase temperature region for temperature-sensitive hydrogels.Several thermally controlled cases of temperature-sensitive hydrogel including grippers,self-folding boxes,thermally driven origami are presented to illustrate a wide array of complex interesting applications or phenomena.Furthermore,we develop a simple model to theoretically calculate the bending angle of the temperature-sensitive hydrogel bilayers,which has been validated by the finite element simulation results.Our study can provide more insights for optimal design in thermally controlled hydrogels structures.