The modern fishery stock assessment could be conducted by various models, such as Stock Synthesis model with high data requirement and complicated model structure, and the basic surplus production model, which fails to incorporate individual growth, maturity, and fishery selectivity, etc. In this study, the Just Another Bayesian Biomass Assessment (JABBA) Select which is relatively balanced between complex and simple models, was used to conduct stock assessment for yellowfin tuna (Thunnus albacares) in the Atlantic Ocean. Its population dynamics was evaluated, considering the influence of selectivity patterns and different catch per unit effort (CPUE) indices on the stock assessment results. The model with three joint longline standardized CPUE indices and logistic selectivity pattern performed well, without significant retrospective pattern. The results indicated that the stock is not overfished and not subject to overfishing in 2018. Sensitivity analyses indicated that stock assessment results are robust to natural mortality but sensitive to steepness of the stock-recruitment relationship and fishing selectivity. High steepness was revealed to be more appropriate for this stock, while the fishing selectivity has greater influence to the assessment results than life history parameters. Overall, JABBA-Select is suitable for the stock assessment of Atlantic yellowfin tuna with different selectivity patterns, and the assumptions of natural mortality and selectivity pattern should be improved to reduce uncertainties. 相似文献
Landslide-prone slopes in earthquake-affected areas commonly feature heterogeneity and high permeability due to the presence of cracks and fissures that were caused by ground shaking. Landslide reactivation in heterogeneous slope may be affected by preferential flow that was commonly occurred under heavy rainfall. Current hydro-mechanical models that are based on a single-permeability model consider soil as a homogeneous continuum, which, however, cannot explicitly represent the hydraulic properties of heterogeneous soil. The present study adopted a dual-permeability model, using two Darcy-Richards equations to simulate the infiltration processes in both matrix and preferential flow domains. The hydrological results were integrated with an infinite slope stability approach, attempting to investigate the hydro-mechanical behavior. A coarse-textured unstable slope in an earthquake-affected area was chosen for conducting artificial rainfall experiment, and in the experiment slope, failure was triggered several times under heavy rainfall. The simulated hydro-mechanical results of both single- and dual-permeability model were compared with the measurements, including soil moisture content, pore water pressure, and slope stability conditions. Under high-intensity rainfall, the measured soil moisture and pore water pressure at 1-m depth showed faster hydrological response than its simulations, which can be regarded as a typical evidence of preferential flow. We found the dual-permeability model substantially improved the quantification of hydro-mechanical processes. Such improvement could assist in obtaining more reliable landslide-triggering predication. In the light of the implementation of a dual-permeability model for slope stability analysis, a more flexible and robust early warning system for shallow landslides hazard in coarse-textured slopes could be provided. 相似文献
During the self-weight penetration process of the suction foundation on the dense sand seabed, due to the shallow penetration depth, the excess seepage seawater from the outside to the inside of the foundation may cause the negative pressure penetration process failure. Increasing the self-weight penetration depth has become an important problem for the safe construction of the suction foundation. The new suction anchor foundation has been proposed, and the self-weight penetration characteristics of the traditional suction foundation and the new suction anchor foundation are studied and compared through laboratory experiments and analysis. For the above two foundation types, by considering five foundation diameters and two bottom shapes, 20 models are tested with the same penetration energy. The effects of different foundation diameters on the penetration depth, the soil plug characteristics, and the surrounding sand layer are studied. The results show that the penetration depth of the new suction foundation is smaller than that of the traditional suction foundation. With the same penetration energy, the penetration depth of the suction foundation becomes shallower as the diameter increases. The smaller the diameter of the suction foundation, the more likely it is to be fully plugged, and the smaller the height of the soil plug will be. In the stage of self-weight penetration, the impact cavity appears around the foundation, which may affect the stability of the suction foundation.