All-silica zeolites screening for capture of toxic gases from molecular simulation

The exhaust gases, including SO_2,NH_3, H_2S, NO_2, NO, and CO, are principal air pollutants due to their severe harms to the ecological environment.Zeolites have been considered as good absorbent candidates to capture the six exhaust gases.In this work, we performed grand canonical ensemble Monte Carlo(GCMC) simulations to examine the capability of 95 kinds of all-silica zeolites in the removal of the six toxic gases, and to predict the adsorption isotherms of the six gases on all the zeolites.The simulation results showed that, H_2S, NO, NO_2, CO and NH_3 are well-captured by zeolite structures with accessible surface area of 1600–1800 m^2·g^(-1) and pore diameter of 0.6–0.7 nm, such as AFY and PAU, while SO_2 is well-adsorbed by zeolites containing larger accessible surface area(1700–2700 m^2·g^(-1)) and pore diameter(0.7–1.4 nm) at room temperature and an atmospheric pressure.However, at saturated adsorption, zeolites RWY, IRR, JSR, TSC, and ITT are found to exhibit better abilities to capture these gases.Our study provides useful computational insights in choosing and designing zeolite structures with high performance to remove toxic gases for air purification, thereby facilitating the development and application of exhaust gas-processing technology in green industry.

Automatic detection and assessment of crack development in ultra-high performance concrete in the spatial and Fourier domains

Automatic detection and assessment of surface cracks are beneficial for understanding the mechanical performance of ultra-high performance concrete(UHPC).This study detects crack evolution using a novel dynamic mode decomposition(DMD)method.In this method,the sparse matrix‘determined’from images is used to reconstruct the foreground that contains cracks,and the global threshold method is adopted to extract the crack patterns.The application of the DMD method to the three-point bending test demonstrates the efficiency in inspecting cracks with high accuracy.Accordingly,the geometric features,including the area and its projection in two major directions,are evaluated over time.The relationship between the geometric properties of cracks and load-displacement curves of UHPC is discussed.Due to the irregular shape of cracks in the spatial domain,the cracks are then transformed into the Fourier domain to assess their development.Results indicate that crack patterns in the Fourier domain exhibit a distinct concentration around a central position.Moreover,the power spectral density of cracks exhibits an increasing trend over time.The investigation into crack evolution in both the spatial and Fourier domains contributes significantly to elucidating the mechanical behavior of UHPC.

Full-scale experiment for segmental linings of deep-buried shield tunnels bearing high inner water pressure:Comparison of mechanical behaviors of continuous-and stagger-jointed structures

Full-scale loading tests were performed on shield segmental linings bearing a high earth pressure and high inner water pressure,focus-ing on the effects of the inner water load and assembly manner on the mechanical properties of the segmental linings.The test results indicate that the deep-buried segmental linings without inner pressure have a high safety reserve.After the action of high inner water pressure,the lining deformation will increase with the reduction of the safety reserve,caused by the significant decrease in the axial force in the linings.Because the bending moment at the segmental joints is transferred to the segment sections in the adjacent ling rings,the convergence deformation,openings of segmental joints,and bolt strains are smaller for the stagger-jointed lining than those for the continuous-jointed lining;however,dislocations appear in the circumferential joints owing to the stagger-jointed assembly.Although it significantly improves the mechanical performance of the segmental lining,stagger-jointed assembly results in compromising the water-proofing safety of circumferential joints.The stagger-jointed assembly manner can be considered to improve the service performance of shield tunnels bearing high inner water pressure on the premise that circumferential joint waterproofing is satisfied.

Experimental study on effect of ductile-iron panel stiffness on mechanical properties of segmental joints of shield tunnels

In circular shield tunnels bearing high inner pressure or rectangular shaped shield tunnels,as the axial force at the segmental lining decreases,the bolt load at the segmental joint increases.It is essential to adopt high-stiffness segmental joints to improve the bearing capacity and control the deformation at the joint position.When designing high-stiffness segmental joints,the selection of ductileiron joint panel is crucial.In this study,two types of segmental joints with different joint panels were fabricated,and the effects of joint panel stiffness on the mechanical properties of segmental joints were analyzed through full-scale sagging and hogging bending tests.The results showed that the failure mode of high-stiffness segmental joint was similar to that of large eccentric compression section.According to the difference of panel stiffness,the failure modes can be specified into two types.If the stiffness is sufficient,the joint failure occurs due to the yielding of bolts;otherwise,it occurs due to the large deformation of ductile-iron joint panels.As for the design requirement of segmental joint,the stiffness of joint panel should be sufficient,i.e.,the opening and failure of the joints are finally induced by the bolt deformation.Otherwise,before the plastic deformation of the bolts,the large deformation of the joint panels will occur under a bendingmoment-dominant load,and the bearing capacity of the joints will greatly decrease.

Infinite horizon H-two/H-infinity control for descriptor systems:Nash game approach

This paper studies the infinite time horizon mixed H-two/H-infinity control problem for descriptor systems using Nash game approach. A necessary/sufficient condition for the existence of infinite horizon H-two/H-infinity control is presented in the form of two coupled algebraic Riccati equations, respectively. Finally, a suboptimal H-two/H-infinity controller design is given based on an iterative linear matrix inequality algorithm.