Bayesian networks are known for providing an intuitive and compact representation of probabilistic information and allowing the creation of models over a large and complex domain. Bayesian learning and reasoning are nontrivial for a large Bayesian network. In parallel, it is a tough job for users (domain experts) to extract accurate information from a large Bayesian network due to dimensional difficulty. We define a formulation of local components and propose a clustering algorithm to learn such local components given complete data. The algorithm groups together most inter-relevant attributes in a domain. We evaluate its performance on three benchmark Bayesian networks and provide results in support. We further show that the learned components may represent local knowledge more precisely in comparison to the full Bayesian networks when working with a small amount of data.
In engineering applications, narrow backfills are often squeezed by retaining walls. Insufficient information is available with respect to the passive earth pressure, whereas the active earth pressure of narrow backfills against retaining walls has been considerably investigated. In this study, the passive failure mechanism of a narrow cohesionless backfill under translation mode has been investigated via a finite element lower-bound limit analysis, considering the effect of backfill geometries and external friction on the failure mechanism. Multiple-slip surfaces could be observed in a narrow backfill in the passive limit state. Further, we summarized the number of slip surfaces under various conditions and proposed a fitting function for the inclined angles of the slip surfaces. In addition, a multiple-slip surface calculation mode was developed. Subsequently, a method was derived for calculating the passive earth pressure of a narrow cohesionless backfill using the differential slice element method, the wedge limit equilibrium, and the finite difference method. Parametric studies explored the effects of the backfill geometries and internal and external frictions on the passive earth pressure. The results demonstrated an increase in the passive earth pressure and the number of slip surfaces when the backfill space decreased, in which the passive earth pressure was nonlinearly distributed.
When a retaining wall is adjacent to a natural slope, the overturning of the wall is usually caused by a yielding foundation. At the point of overturning, the narrow backfill behind the wall has reached the active limit state. However, in previous studies, the foundation conditions of the retaining wall were not fully considered when the earth pressure on the retaining wall with the narrow backfill was calculated. To comprehensively consider the stress state of the retaining wall, the finite-element limit analysis method was employed to study the failure mode of a retaining wall adjacent to a natural slope. The simulation results indicate that the sliding surface starts from the wall heel, with one side developing at the surface of the natural slope and the other developing in the ground in front of the wall. Based on this failure mechanism, a slip-line computational model for the retaining wall was established. When the slip-line solution was compared with the finite-element solution, the results were in good agreement. The plastic zone of the soil was determined by the slip-line field. In addition, the slip-line solution gave the active earth pressure of the narrow backfill, the passive earth pressure of the soil in front of the wall, and the foundation bearing capacity. Moreover, several extensive parametric studies were conducted. Thus, the shape of the narrow backfill, the rough soil–wall interface, and the low-strength backfill are all conducive to reducing active earth pressure on a retaining wall.
In engineering, the new retaining walls are often constructed near the existing structure owing to the space limitation. The backfill behind the retaining wall is narrow, which causes an overestimation in the active earth pressure by using Coulomb’s earth pressure theory. In previous studies, experimental observations for the failure modes of narrow backfills are still rare. To confirm the failure mode of the narrow backfill, the experimental method and the geotechnical particle image velocimetry method are employed to observe the active failure process of the cohesionless narrow backfill with various widths under the translation mode. The experimental results revealed that the decrease in the length of the backfill width led to the increase in the inclined angle of the sliding surface. When the backfill width was sufficiently small, the sliding surface developed from the wall toe to another wall face, and then another sliding surface occurred as a reflection. In addition, the active earth pressure of the narrow backfill is significantly smaller than that calculated using Coulomb’s method. The active failure calculation models are established based on the experimental results. The active earth pressure of the narrow cohesionless backfill under the translation mode is derived by using the limit equilibrium methods. The proposed method was validated by comparing with the previous method and the experimental data.
COVID-19, which broke out in 2019 in China, is caused by SARS-CoV-2. According to the latest WHO real-time statistics, as of 1:19 p.m. BST on April 22, there were 142557268 cumulative new confirmed cases of coronavirus pneumonia and 3033798 cumulative deaths worldwide. Therefore, it is significant to understand the structure and the pathogenic mechanism of SARS-CoV-2, which is helpful to understand the diagnosis and treatment of sars-cov-2. We primarily investigate related sources on Pubmed and related scholar websites. We found some antiviral drugs such as lopinavir, chloroquine, and its derivative hydroxychloroquine, remdesivir, and arbidol have great potential in the treatment of COVID-19. However, some of them have a serious adverse reaction, reminding us to use them with caution.
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