Effect of carbonation-drying-wetting on durability of coral aggregate seawater concrete

Based on the drying-wetting cycles experiment and the carbonation-drying-wetting cycles experiment for coral aggregate seawater concrete(CASC)with different strength grades,the effects of carbonation-drying-wetting on the durability of CASC are studied with the surface state,mass loss rate,relative dynamic elastic modulus,ultrasonic wave velocity and cube compressive strength as indices.Results show that the mass loss rate of CASC increases gradually with the increase in cycle times in the drying-wetting and carbonation-drying-wetting cycles.The mass loss rate increases relatively slowly at the initial stage but it increases remarkably after 10 cycles.The relative dynamic elastic modulus and ultrasonic wave velocity decrease gradually with the increase in cycle times.After 6 cycles,the decrease rate of the relative dynamic elastic modulus and ultrasonic wave velocity of CASC tends to be flat and the surface is slightly damaged.Compared with the initial 28 d cube compressive strength,the cube compressive strength of CASC decreases by 8.8%to 11.0%.Drying-wetting cycles and carbonation can accelerate seawater erosion on CASC,and drying-wetting cycles result in salting-out and accelerate the destruction of concrete.Therefore,the carbonation-drying-wetting accelerates the destruction of CASC.

Dispersion characteristics of seabed Scholte waves with variable velocity seawater in deep water

Acoustic velocity varies in deep-water environments.To obtain accurate inversion interpretations,it is necessary to develop a horizontally layered seawater–seabed(HLSS)model with continuously varying velocities.In this work,we used an HLSS model based on wave theory to deduce the Scholte wave dispersion equations and established an HLSS model based on the acoustic velocity profile and the submarine medium parameters of the South China Sea.We studied the dispersion characteristics of Scholte waves and theoretically calculated the amplitude–depth distribution.We also examined the influence of deep-water environments on the dispersion characteristics of Scholte waves.Using the real geological parameters of the Dongsha Islands in the South China Sea,we exploited the spectral element method to simulate seismic wave propagation in the fluid–solid interface and extracted the Scholte wave dispersion curves using multichannel analysis of surface waves(MASW).The consistent theoretical and extracted dispersion curve results verified the accuracy of our method.Numerical experiments showed that the dispersion characteristics of Scholte waves in deep water are weaker than those in shallow water.In addition to the seawater depth and the physical parameters of seabed sediments,the seawater’s variable velocity also influences Scholte wave dispersion characteristics.

Effects of a patchy seagrass meadow on the macrobenthic community

Based on macrobenthos collected from intertidal seagrass bed in Guangrao,Shandong Province in May 2013,the macrobenthic structure and diversity were analyzed.A total of 41 macrobenthic species were identified,among which crustaceans were the most speciose macrobenthic taxa(16 species),followed by polychaetes(15 species)and mollusks(10 species).Seven dominant macrobenthic species were identified,including 3 species of polychaetes,2 species of crustaceans and 2 species of mollusks.The total abundance across the whole sampling area was 661.33 ind/m2.Total abundance and the abundance of Potamocorbula laevis and Heteromastus filiformis showed significant spatial variation,and the macrobenthic abundance distributed in seagrass meadows was higher than that in other areas.The results of cluster,nMDS ordination,SIMPER and IMS analyses all showed no linear correlation along the distance gradient from the seagrass meadow.Therefore,degraded seagrass can still provide detectable but limited ecological services.However,the rehabilitation of seagrass bed is essential and urgent to regain their full ecological function.

“水”在中国文学中的形象类别

水不仅是人类社会重要的生活、生产资源,也是重要的审美资源。在文学领域,描写"水"的内容极为丰富。"水"成为具有感染力的文学形象,经过历代延续,已积淀为频繁出现于作家笔下的"传统形象"。中国文学典籍中对水的描写,可以分为实用意义的水形象、审美意义的水形象两大类,后一类又可进一步分为环境形象、本体形象、比喻形象。这些水形象的丰富内涵成为中华水文化的重要内容之一。