Vertical variations and transport mechanism of soil moisture in response to vegetation restoration on the Loess Plateau of China

Soil moisture is essential for vegetation restoration in arid and semi-arid regions. Ascertaining the vertical distribution and transportation of soil moisture under different vegetation types has a profound effect on the ecological construction. In this study, the soil moisture at a depth of 500 cm for four typical vegetation types, including Robinia pseudoacacia, Caragana korshinskii, Stipa bungeana, and corn, were investigated and compared in the Zhifanggou watershed of the Loess plateau. Additionally, hydrogen and oxygen stable isotopes were detected to identify the transport mechanism of soil moisture. The results showed vertical distribution and transportation of soil moisture were different under different vegetation types. Depth-averaged soil moisture under S. bungeana and corn generally increased along the profile, while C. korshinskii and R. pseudoacacia showed weakly increasing and relatively stable after an obvious decreasing trend (0–40 cm). The soil moisture under R. pseudoacacia was lower than that under other vegetation types, especially in deep layer. However, the effect of R. pseudoacacia on soil moisture in the topsoil (< 30 cm) could be positive. For R. pseudoacacia (160–500 cm), C. korshinskii (0–500 cm), and S. bungeana (0–100 cm), the soil moisture declined with increased in vegetation age. Planting arbor species such as R. pseudoacacia intensified the decline of soil moisture on the Loess Plateau. The capacity of evaporation fractionation of soil moisture followed the sequence: corn > S. bungeana > R. pseudoacacia > C. korshinskii. The δ¹⁸O values in soil water fluctuated across the profile. The δ¹⁸O values changed sharply in upper layer and generally remained stable in deep layer. However, in middle layer, the vertical distribution characteristics of the δ¹⁸O values were different under different vegetation types. We estimated that piston flow was the main mode of precipitation infiltration, and the occurrence of preferential flow was related to vegetation types. These results were helpful to improve the understanding of the response of deep soil moisture to vegetation restoration and inform practices for sustainable water management.     

一条巨大的地震活动带（东北深震区－渤海－川滇－缅甸中深震区）的存在

本文研究了东北深震、缅甸中深震、渤海周围地震及川滇地震在活动进程中的关系。在地域分布上彼此相连。并呈以北东向斜贯中国东部浑然为有机整体巨大的地震带。同时还研究了东北深震与华北东部的渤海周围地震以及缅甸中深震与川滇地震活动的相关性和前兆性。指出了这些特点，对华北东部地震和川滇地震的预测是十分有意义的。文章在最后还讨论了太平洋、印度、欧亚三大板块的相互作用可能是巨大地震带形成的主要条件和产生变动的重要的动力因素。     

宁夏银川水洞沟遗址2号点晚更新世晚期孢粉记录的古环境

宁夏银川水洞沟遗址2号点剖面孢粉分析结果表明:该地区在晚更新世晚期孢粉组合以草本植物花粉占绝对优势,有Chenopodiaceae、Artemisia、Zygophyllum、Ranunculaceae和少量的Euonymus、Ephedra和Nitraria等,木本植物花粉次之,有Pinus、Picea、Abies、...     

基于稳定同位素方法的吕泗渔场近岸海域主要生物潜在碳源及营养级分析

基于稳定同位素方法,对2018年吕泗渔场近岸海域夏季主要生物种类的潜在碳源及其营养级进行分析,利用IsoSource模型计算该海域消费者的3大碳源（浮游植物、悬浮颗粒有机物、底质有机物）贡献值,并比较叠加潜在碳源影响前后主要生物种类的营养级变化。结果表明,浮游植物和底质有机物对37种主要生物种类的贡献比例分别为58.7%和28.2%,而悬浮颗粒有机物的贡献较小。因此判定吕泗渔场近岸海域夏季主要生物种类的潜在碳源主要是浮游植物和底质有机物。通过分别叠加3大潜在碳源和单一物种作为基准值构建两个营养级谱,右营养级谱的生物种类营养级范围为1.74～3.92,比左营养级谱平均下降0.19个营养级,尽管两个营养级谱的整体趋势走向不变,但部分鱼类和多数虾类的营养位置发生改变。右营养级谱的基准值随着潜在碳源叠加比例的不同而变化,能有效反映生物营养级,更适用于低营养级的虾蟹类。但对于处于中高级消费者位置的鱼类来说,这种叠加的效果影响不大。     

Numerical simulation of water flooding into a damaged vessel’s compartment by the volume of fluid method

When a vessel is damaged, seawater floods into the damaged compartments and subsequently influences the motion of the vessel. Furthermore, the vessel’s behaviour affects the floodwater motion. In this paper, a Navier-Stokes (NS) solver with a free surface capturing technique, i.e., the volume of fluid (VOF) method, was developed to numerically simulate water flooding into a damaged vessel. To verify the developed solver, a 2-D and a 3-D dam break problems were tested. The numerical results coincide well with the experimental results and with the published numerical results. Additionally, it was used to solve the problems of linear and non-linear liquid sloshing in a hexahedral tank. The numerical results are satisfactory in comparison with the experimental results and analytical solutions. Finally, the phenomenon of water flooding into a damaged compartment of a Ro-Ro ferry was simulated numerically. The computed results are in good agreement with the experimental data.     

Genetic variation of the small yellow croaker (Larimichthys polyactis) inferred from mitochondrial DNA provides novel insight into the fluctuation of resources

The small yellow croaker (Larimichthys polyactis) belongs to the family Sciaenidae, which is an offshore warm fish species and widely distributed in the western Pacific. In this study, the variation of genetic diversity and genetic differentiation among L. polyactis populations was analyzed by mitochondrial DNA control region. A total of 110 polymorphic sites were checked, which defined 134 haplotypes. High level of haplotype diversity (h=0.993±0.002) was detected in the examined range. Population genetic structure analyse (analysis of molecular variance, F_st) showed there were high gene flow among L. polyactis populations. The result showed that there were relatively high genetic diversity and low genetic differentiation among the Yellow Sea and the East China Sea populations, which can be attributed to diverse habitats, wide distribution range and high mutation rate of control region. Using phylogenetic methods, coalescent analyses (neutrality tests, mismatch distribution analysis, Bayesian skyline analyses) and molecular dating interpreted in conjunction with paleoclimatic and physiographic evidence, we inferred that the genetic make-up of extant populations of L. polyactis was shaped by Pleistocene environmental impacts on the historical demography of this species. Besides, relatively constant genetic diversity and larger effective population size were detected in recent L. polyactis population. The result showed that the fishing policy certainly, such as the summer closed fishing, played a role in protecting resources of L. polyactis. This study can offer a wealth of biological novelties which indicates genetic structure of L. polyactis population and provides the foundation for resources protection and policy setting.     

Dynamic Response Analysis and Vibration Control for A Fixed-Bottom Offshore Wind Turbine Subjected to Multiple External Excitations

For the offshore wind turbines installed in earthquake areas, their operation is affected by seismic loads in addition to wind and wave loads. Therefore, it is necessary to study the dynamic responses and vibration control of the wind turbines. In previous studies, the structural responses of offshore wind turbines are usually investigated in the parked case, while the blade rotation effect is usually not considered. The evaluation on the structural responses may be inaccurate under this conditi...     

贻贝粉酶解液提取复合氨基酸

报道了以脱脂后的贻贝粉为原料，采用酶解法从其酶解液中分离提取复合氨基酸的工艺。其收率为２０％，纯度约为９０％。其中必需氨基酸（不计色氨酸）约占复合氨基酸总量的５５％，其氨基酸模式与ＦＡＯ／ＷＨＯ组织确定的模式及人乳模式进行了对照，通过适量添加个别氨基酸可使其配比接近人乳模式。     

Prediction of one-dimensional compression behavior of Nansha clay using fractional derivatives

Nansha clay is an interactive marine and terrestrial deposited soft clay that is widely spread in Guangzhou, Pearl River Delta, China. To avoid excessive settlement after construction, there is a need for better quantifying the time-dependent deformation of the soft clay. This paper presents a preliminary study to predict the one-dimensional compression of Nansha clay using fractional derivatives. A fractional Merchant model was introduced to describe the time-dependent settlement, and analytical solutions were obtained in terms of the Mittag-Leffler function. The oedometer test results were presented to validate this model. Compared with classical rheological models, the fractional derivative-based model enabled close estimation of the one-dimensional compression with fewer parameters. The meaning of the order of fractional derivative and its relationship with the clay physical properties were explored. It shows that a smaller value of this order corresponded to a higher coefficient of consolidation and a lower coefficient of secondary consolidation. The amplitude of both the primary and secondary consolidation of clay may be estimated quantitatively by the order of fractional derivative. Taken together, these results may open up new avenues for theoretical and empirical modeling of rheological phenomena in clay using fractional derivatives.