Investigation Progresses and Applications of Fractional Derivative Model in Geotechnical Engineering

Over the past couple of decades, as a new mathematical tool for addressing a number of tough problems, fractional calculus has been gaining a continually increasing interest in diverse scientific fields, including geotechnical engineering due primarily to geotechnical rheology phenomenon. Unlike the classical constitutive models in which simulation analysis gradually fails to meet the reasonable accuracy of requirement, the fractional derivative models have shown the merits of hereditary phenomena with long memory. Additionally, it is traced that the fractional derivative model is one of the most effective and accurate approaches to describe the rheology phenomenon. In relation to this, an overview aimed first at model structure and parameter determination in combination with application cases based on fractional calculus was provided. Furthermore, this review paper shed light on the practical application aspects of deformation analysis of circular tunnel, rheological settlement of subgrade, and relevant loess researches subjected to the achievements acquired in geotechnical engineering. Finally, concluding remarks and important future investigation directions were pointed out

Mechanical behaviors of surrounding rock and supporting structure of shallow-buried unsymmetrical pressure tunnel crossing soil–rock interface

Shallow bias tunnels are sensitive at the entrance section, where the existence of soil–rock interface (SRI) results in more complex deformation of surrounding rock and supporting structure. This study investigates the mechanical properties of surrounding rock and supporting structure of a shallow-buried bias tunnel crossing the soil–rock interface by a combination of model tests and numerical simulations. A shallow-buried biased tunnel with significant cracking at its entrance section is selected in southwest China. The plastic zone distribution, deformation, and pressure of surrounding rock, as well as the stress and deformation of supporting structure, are analyzed under different conditions with the tunnel vault, arch haunch, arch spring, and wall foot crossing the soil–rock interface. The test and numerical results show that the internal force of the lining structure is the largest at the left arch haunch and the right arch spring, with cracks occurring in the project. The surrounding rock and supporting structure are most prominently influenced by the arch haunch and arch spring crossing the soil–rock interface among different positions of the tunnel. The supporting structure is subjected to stress in three modes: there is mainly shearing when the tunnel vault passes through the soil–rock interface, extrusion and shearing co-exist when the tunnel arch haunch and arch spring pass through the soil–rock interface, and extrusion is dominant when the tunnel wall foot passes through the soil–rock interface. Inserting grouting steel pipes perpendicular to the soil–rock interface on the deep-buried side of the tunnel can effectively control the deformation of surrounding rock and the stress of supporting structure

Event-triggered optimal control of completely unknown nonlinear systems via identifier-critic learning

summary:This paper proposes an online identifier-critic learning framework for event-triggered optimal control of completely unknown nonlinear systems. Unlike classical adaptive dynamic programming (ADP) methods with actor-critic neural networks (NNs), a filter-regression-based approach is developed to reconstruct the unknown system dynamics, and thus avoid the dependence on an accurate system model in the control design loop. Meanwhile, NN adaptive laws are designed for the parameter estimation by using only the measured system state and input data, and facilitate the identifier-critic NN design. The convergence of the adaptive laws is analyzed. Furthermore, in order to reduce state sampling frequency, two kinds of aperiodic sampling schemes, namely static and dynamic event triggers, are embedded into the proposed optimal control design. Finally, simulation results are presented to demonstrate the effectiveness of the proposed event-triggered optimal control strategy

Biomaterials research of China from 2013 to 2017 based on bibliometrics and visualization analysis

Objectives This study aims to evaluate the changes of development trends and research hotspots of biomaterials research from 2013 to 2017, which can identify the general information of papers and explore the changes of research content, thus providing perspectives for the development of biomaterials in China and other countries. Methods Data of the paper were retrieved from the Web of Science Core Collection, and then analyzed by the bibliometric and CiteSpace visualization analysis. Results It was found that a total of 3,839 related papers had been published from the year 2013 to 2017. The analysis of the articles showed that the annual quantity and quality of the articles in the biomaterials research have been increasing since 2013, and the Wang L / Chinese Academy of Sciences were the most productive author/institution. Meanwhile, the keywords “in vitro”, “scaffold”, “nanoparticle” , “mechanical property”, and “biocompatibility” have the relatively higher frequency, and the keywords “apatite”, “deposition”, and “surface modification” have the strongest burst citation. Conclusions After statistics and analysis, we found that biomaterials is a promising research field. The study may be helpful in understanding research trends in this field

Stress Analysis of CFG Pile Composite Foundation in Consolidating Saturated Mine Tailings Dam

Cement fly-ash gravel (CFG) pile is a widely used ground reinforcement technique. This paper aims to address the mechanical characteristics of CFG composite foundation in consolidating saturated mine tailings (MTs) dam. The field static load tests were employed to explore the bearing capacity of the CFG composite foundation, and finite element (FE) models in three dimensions validated through comparison with experimental results were used to discuss the pile-soil stress distribution and pile-soil stress ratio of the CFG composite foundation. The results indicate that the distribution of earth pressure and pile stress is relatively homogeneous and stable over depth and load, while the development of CFG composite foundation bearing capacity is insufficient, in which the developed bearing capacity of CFG piles is less than 50% of its characteristic value. Additionally, compared with the laboratory model test results, the pile-soil stress ratio decreases with the increasing of the load in FEM results proved to better conform to the actual engineering conditions. Furthermore, the deformation modulus and thickness of cushion exert significant influence on pile-soil stress ratio and integral bearing capacity of CFG composite foundation

The Transcription Factor TCF1 Preserves the Effector Function of Exhausted CD8 T Cells During Chronic Viral Infection

The long-term persistence of viral antigens drives virus-specific CD8 T cell exhaustion during chronic viral infection. Yet exhausted, CD8 T cells are still endowed with certain levels of effector function, by which they can keep viral replication in check in chronic infection. However, the regulatory factors involved in regulating the effector function of exhausted CD8 T cell are largely unknown. Using mouse model of chronic LCMV infection, we found that the deletion of transcription factor TCF-1 in LCMV-specific exhausted CD8 T cells led to the profound reduction in cytokine production and degranulation. Conversely, ectopic expression of TCF-1 or using agonist to activate TCF-1 activities promotes the effector function of exhausted CD8 T cells. Mechanistically, TCF-1 fuels the functionalities of exhausted CD8 T cells by promoting the expression of an array of key effector function-associated transcription regulators, including Foxo1, Zeb2, Id3, and Eomes. These results collectively indicate that targeting TCF-1 mediated transcriptional pathway may represent a promising immunotherapy strategy against chronic viral infections by reinvigorating the effector function of exhausted virus-specific CD8 T cells

Praziquantel Facilitates IFN-γ-Producing CD8+ T Cells (Tc1) and IL-17-Producing CD8+ T Cells (Tc17) Responses to DNA Vaccination in Mice

BACKGROUND: CD8(+) cytotoxic T lymphocytes (CTLs) are crucial for eliminating hepatitis B virus (HBV) infected cells. DNA vaccination, a novel therapeutic strategy for chronic virus infection, has been shown to induce CTL responses. However, accumulated data have shown that CTLs could not be effectively induced by HBV DNA vaccination. METHODOLOGY/PRINCIPAL FINDINGS: Here, we report that praziquantel (PZQ), an anti-schistoma drug, could act as an adjuvant to overcome the lack of potent CTL responses by HBV DNA vaccination in mice. PZQ in combination with HBV DNA vaccination augmented the induction of CD8(+) T cell-dependent and HBV-specific delayed hypersensitivity responses (DTH) in C57BL/6 mice. Furthermore, the induced CD8(+) T cells consisted of both Tc1 and Tc17 subtypes. By using IFN-γ knockout (KO) mice and IL-17 KO mice, both cytokines were found to be involved in the DTH. The relevance of these findings to HBV immunization was established in HBsAg transgenic mice, in which PZQ also augmented the induction of HBV-specific Tc1 and Tc17 cells and resulted in reduction of HBsAg positive hepatocytes. Adoptive transfer experiments further showed that PZQ-primed CD8(+) T cells from wild type mice, but not the counterpart from IFN-γ KO or IL-17 KO mice, resulted in elimination of HBsAg positive hepatocytes. CONCLUSIONS/SIGNIFICANCE: Our results suggest that PZQ is an effective adjuvant to facilitate Tc1 and Tc17 responses to HBV DNA vaccination, inducing broad CD8(+) T cell-based immunotherapy that breaks tolerance to HBsAg

The time invariant beamformer for Doppler spread suppression in high‐mobility transmission

Abstract Beamforming network with the Doppler suppression scheme reducing the channel time‐varying effects has attracted much research interests in high‐mobility massive MIMO communications. However, the current time‐varying beamforming network still suffers from high volatility peak‐to‐average power ratio (PAPR) fluctuations. For this reason, a time invariant compensation optimized beamformer is proposed to mitigate the peak‐to‐average power ratio high volatility and the channel time variation in the high‐mobility uplink transmission. To attain the Doppler spread and implement the Doppler spread suppression scheme, a time‐varying spectrum (TVS) is proposed and its statistical properties of time‐varying spectrum is analyzed. The simulation results are provided to verify the proposed studies

Exploration of beautiful village renovation against the backdrop of global tourism

With the rise of global tourism, construction of villages is facing changes in development goals and priorities. Facing the tasks of physical environment improvement and function improvement, a multi-dimensional beautiful village renovation system of functions, architecture, environment, and facilities is constructed. Taking the Qixi group of Jiangkou village, Zhangfang Town, Liuyang City as an example, based on the basic characteristics of natural resource, historical and cultural traditions, etc., it has promoted the overall improvement of village functions from four aspects: overall functional layout, building renovation, road renovation, and landscape. The purpose is to explore an effective way to renovate beautiful villages under the background of global tourism, and provide some practical guidance for the future renovation of beautiful villages