Critical Line Research Articles

A novel method for imitating true-triaxial stress path with conventional triaxial apparatus

The stress paths of the cylindrical specimen in the p–q stress space by controlling the ratio of the axial and the radial loading is guaranteed to be consistent with the cuboid specimen, a novel method for imitating true-triaxial stress path by conventional triaxial apparatus was presented. Under the condition that p and q were variables and b was constant, the true-triaxial stress paths were realized by conventional triaxial apparatus strictly and easily. Under the condition that b and p were invariants, the b was used to control the ratio of axial and radial loading to ensure p constant, the method can be used to measure the strength on the π plane. If the tests were conducted at the different p with the same b, the critical state line of different b could be obtained. Under the condition that p and q were constant, the proposed method of nonlinear loading with b as a parameter could be used to design the various stress paths of true-triaxial under the condition of deviatoric stress consolidation, and which could be used to determine the deformation and the plastic flow of soil in 3D space. The proposed method could be used to achieve the equivalent stress path in the p–q stress space to obtain the 3D mechanical properties, and the stress path controlled by stress, strain, and a hybrid of stress and strain. Once the software of conventional triaxial apparatus was developed by the novel method, the measuring range of stress paths could be expanded greatly.

Blume-Capel model analysis with a microcanonical population annealing method.

We present a modification of the Rose-Machta algorithm [N. Rose and J. Machta, Phys. Rev. E 100, 063304 (2019)2470-004510.1103/PhysRevE.100.063304] and estimate the density of states for a two-dimensional Blume-Capel model, simulating 10^{5} replicas in parallel for each set of parameters. We perform a finite-size analysis of the specific heat and Binder cumulant, determine the critical temperature along the critical line, and evaluate the critical exponents. The obtained results are in good agreement with those previously obtained using various methods-Markov chain Monte Carlo simulation, Wang-Landau simulation, transfer matrix, and series expansion. The simulation results clearly illustrate the typical behavior of specific heat along the critical lines and through the tricritical point.

Effects of microbially induced calcite precipitation on static liquefaction behavior of a gold tailings sand

Loose tailings are susceptible to static liquefaction during which they lose a substantial amount of their strength. This study examines a sustainable technique known as Microbially-Induced Calcite Precipitation (MICP) to improve the static liquefaction resistance of gold mine silty sand tailings. These materials were enriched with Sporosarcina pasteurii, consolidated in a direct simple shearing apparatus, and subjected to several injections of a cementation solution. Calcified tailings were then sheared under constant-volume and constant vertical stress conditions to evaluate their undrained and drained shearing behaviors. Results showed that bio-mineralization can prevent the occurrence of static liquefaction in tailings by reducing their contraction tendency. This is demonstrated by the strong strain-hardening behaviors of the treated tailings specimens compared to the strain-softening and undrained strength loss in specimens of the untreated tailings. Substantial increases in the tailings undrained and drained shear strengths (by up to 30 - 50 kPa), improvements (by up to 5 MPa) in their tangent moduli, and more than 5° rise in their friction angles are observed in the direct simple shear tests following MICP-treatment. The critical state line of tailings is also found to be steeper and shifted to denser void ratios following MICP treatment. These changes reduce liquefaction susceptibility of tailings and enhance their resistance against static liquefaction. Post-treatment acid dissolution further indicates that CaCO3 contents of about 4% to 11% precipitated in the treated specimens. This amount decreases with increasing specimens void ratio. Changes in the microstructural fabric of the cemented tailings particles are also characterized using scanning electron microscopic (SEM) images and X-ray diffraction (XRD) analyses.

Bound state energies and critical bound region in the semiclassical dense hydrogen plasmas

We calculate the bound state energies of the hydrogen atom in semiclassical dense hydrogen plasmas modeled by the effective screened interaction potential developed by Ramazanov et al. [Phys. Rev. E 92, 023104 (2015)]. It is shown that the quantum degenerate and exchange-correlation effects of plasma electrons do not play significant roles in the region where the system exhibits bound states. The bound-continuum critical transition lines and the distribution of the ground state energies in the plasma density-temperature phase diagrams are obtained, both with and without taking into account the screening effect of the plasma ions. The dipole transition oscillator strengths and static dipole polarizabilities of the electron-ion subsystems in semiclassical dense hydrogen plasmas are calculated in a wide range of plasma parameters.

A simple gradation-state-dependent model for granular materials

This paper proposes a gradation-state-dependent constitutive model to capture the granular materials' mechanical behaviours considering the granular crushing's influence. Firstly, a gradation evolution law is developed to reflect the change in grain size distribution (GSD) with the growth of stress levels, and then, based on the evolution law, the elastic compliance matrix is modified to reflect the effects of particle breakage. Secondly, as the critical state line (CSL) exhibits gradation dependence, a novel method is developed to describe the family of CSLs under different fixed gradations. Subsequently, by combining the gradation evolution law with the CSL equation, the paper explains the steepening of the slope of the critical state line when the crushing is activated. With the improvement of CSL, the material's shear dilatancy and contraction properties are better reflected, assisting in establishing a plastic compliance matrix. Employing the derived elastic and plastic compliance matrix, the elastic–plastic model reflecting the influence of gradation and state effects is established and verified with a series of experimental and discrete element method (DEM) simulation results.

Numerical study of CO2 trans-critical process inside micromodel based porous structures under supercritical pressures

Understanding the flow, heat transfer, and trans-critical process of carbon dioxide in porous media is crucial for various applications, including CO2 sequestration, soil remediation and oil and gas recovery, due to its unique physical properties in the critical region. In this study, a porous media model on a microfluidic chip structure was simulated to emphasize the heat transfer and trans-critical process of CO2 under supercritical pressure in porous media. The study aims to observe the behaviors of CO2 during its transition from subcritical to supercritical temperature under supercritical pressure. The main objective is to observe the temperature distribution and pressure change of CO2 in a porous media model under the influence of bottom heating. At the same time, we observe the changes in the position of the critical temperature point of CO2 in porous media and analyze its heat exchange process in porous media. After the flow reaches a steady state, the temperature span near the grains is 1.6 K, and the pressure drop per unit length is 1480.3 Pa/mm. As the flow time progresses, the critical temperature line migrates from outlet region to inlet region, the range of sCO2 narrows from 81.7 % to 84.7 % in the porous media region. Finally, the influence of different working conditions on the trans-critical region is studied. It is hoped that this study will contribute to the understanding of the trans-critical process of CO2 in porous media.

Machine learning framework develops neutrophil extracellular traps model for clinical outcome and immunotherapy response in lung adenocarcinoma.

Neutrophil extracellular traps (NETs) are novel inflammatory cell death in neutrophils. Emerging studies demonstrated NETs contributed to cancer progression and metastases in multiple ways. This study intends to provide a prognostic NETs signature and therapeutic target for lung adenocarcinoma (LUAD) patients. Consensus cluster analysis performed by 38 reported NET-related genes in TCGA-LUAD cohorts. Then, WGCNA network was conducted to investigate characteristics genes in clusters. Seven machine learning algorithms were assessed for training of the model, the optimal model was picked by C-index and 1-, 3-, 5-year ROC value. Then, we constructed a NETs signature to predict the overall survival of LUAD patients. Moreover, multi-omics validation was performed based on NETs signature. Finally, we constructed stable knockdown critical gene LUAD cell lines to verify biological functions of Phospholipid Scramblase 1 (PLSCR1) in vitro and in vivo. Two NETs-related clusters were identified in LUAD patients. Among them, C2 cluster was provided as "hot" tumor phenotype and exhibited a better prognosis. Then, WGCNA network identified 643 characteristic genes in C2 cluster. Then, Coxboost algorithm proved its optimal performance and provided a prognostic NETs signature. Multi-omics revealed that NETs signature was involved in an immunosuppressive microenvironment and predicted immunotherapy efficacy. In vitro and in vivo experiments demonstrated that knockdown of PLSCR1 inhibited tumor growth and EMT ability. Besides, cocultural assay indicated that the knockdown of PLSCR1 impaired the ability of neutrophils to generate NETs. Finally, tissue microarray (TMA) for LUAD patients verified the prognostic value of PLSCR1 expression. In this study, we focus on emerging hot topic NETs in LUAD. We provide a prognostic NETs signature and identify PLSCR1 with multiple roles in LUAD. This work can contribute to risk stratification and screen novel therapeutic targets for LUAD patients.

A universal lower bound for certain quadratic integrals of automorphic L–functions

Let π be a cuspidal unitary representation od GL(m,A) where A denotes the ring of adèles of Q. Let L(s,π) be its L-function. We introduce a universal lower bound for the integral ∫−∞+∞|L(12+it,π)12+it−s|2dt where s is equal to 0 or is a zero of L(s) on the critical line. In the main text, the proof is given for m≤2 and under a few assumptions on π. It relies on the Mellin transform; the proof involves an extension of a deep result of Friedlander-Iwaniec. An application is given to the abscissa of convergence of the Dirichlet series L(s,π). In the Appendix, written with Peter Sarnak, the proof is made unconditional for general m.

Experimental study of secondary oil droplet formation during coalescence process of oil Droplet-Gas bubble

Flotation is an efficient pretreatment technology for oily water. In this study, the coalescence processes of air bubbles and isooctane droplets with different size ratios, 1.0–2.2, were investigated using a high-speed imaging system. Two types of oil droplet-gas bubble interaction have been identified: full coalescence and partial coalescence. Through analysis of interfacial force at the liquid bridge, it has been observed that interfacial force at the oil droplet bridge affects the lateral contraction of the liquid bridge, which in turn affects the coalescence of oil droplets and gas bubbles. Through dimensional analysis, a phase diagram of dimensional parameter coalescence behavior has been constructed, and the critical line of partial coalescence and full coalescence has been determined. This work fills the void in the study of secondary oil droplet coalescence within the oil droplet-gas bubble coalescence in gas flotation, which is potentially applied for industrial air flotation system design and optimization.

Addressing climate change in high school in Senhor do Bonfim - BA: a commitment to a sustainable future

This article discusses the need to address climate change in high school education in Senhor do Bonfim, Bahia, focusing on Cartography as an educational tool. Initially, it presents the global relevance of climate change and emphasizes the importance of addressing it at the local level. The general objective of this article is to discuss how the approach to climate change in Senhor do Bonfim's high school can contribute to a sustainable future. The specific objective is to demonstrate how the use of Cartography as an educational tool can increase students' awareness of local and global climate change. The article highlights the global relevance of climate change, highlighting that this is a challenge that affects the entire planet. However, it underscores the importance of addressing climate change at the local level, as local communities are also affected by extreme weather events and environmental degradation. To this end, the methodology used follows the dialectical critical line with a qualitative approach. To work on the concepts, a bibliographic survey was conducted, focusing on issues such as climate change, Cartography, and environmental preservation. The methodological procedure used was a case study of a field trip to Serra do Gado Bravo with high school students in the municipality in question, which served as the basis for the development of this work.

Suits and “game-playing”: formalism and subjectivism revisited. A critique

ABSTRACT In his work, Bernard Suits presents and pursues a stated objective: to define ‘game’ or, more precisely, ‘game-playing’. In The Grasshopper: Games, Life and Utopia, the author seeks a definition not as a ‘commitment to the universal fruitfulness of definition construction’, but rather with the idea ‘that some things are definable, and some are not’. This is something he believed could resolve many of the issues surrounding the debate on ‘game’ and ‘play’, such as those with Huizinga (in Homo Ludens) or proposed by the anti-definitionism of Wittgenstein, a philosopher who did not accept that it was possible to define ‘game’. In this article, we will trace Suits’ definitional steps and aim to critique his resolution as a kind of ‘formalism’, as it tended to prioritize rules. Furthermore, notwithstanding the merit of his theoretical endeavor – seen in the attempt to define a social component that is so complex and the target of the most diverse interpretations and misconceptions –, it seems to us that, with his theoretical unifying element (lusory attitude), the author has summoned another problem to the debate, that of ‘subjectivism’, rather than a solution (especially to his formalism), even subjecting himself to comparisons with other conceptions (e.g. Fichte) that are also problematic. This aspect will also be criticized. The attention of this article will shift to these two lines of critique, drawing on an insightful analysis of Malaby’s work at a specific juncture, aiming to delve further into the subject and taking an additional step.

Discrete element study of the effect of particle shape on critical state characteristics and constitutive parameters of sand

Based on the discrete element particle flow software PFC3D, four irregular particles with the same aspect ratio, convexity, and sphericity as the binary pictures are constructed. To examine the influence mechanisms of particle shape on mechanical properties, microstructure, and critical characteristics, an index F characterizing the regularity of the particle shape is introduced. By examining the link between the regularity index and the constitutive parameter, a statistical model is developed to predict the peak friction angle while considering the impacts of relative density and particle shape. The findings demonstrate that decreasing the value of the regularity index always causes an increase in the stress ratio, shear dilatancy, and void ratio. In p'-q, e-logp’, and MCN-logp’ spaces, the distribution pattern of critical state lines is affected by the particle shape. At the same strain instant, when the particle becomes more irregular, the distribution direction of the maximum contact force of irregular particles tends to be more horizontal to resist the greater external loads. In comparison to spherical particles, the Δq/p' and Δφp of irregular particles increase linearly with the increase of ΔF. The measured and predicted values of the peak friction angle for the statistical model are essentially consistent. The critical parameters ecs、ηcs、φcs、MCNcs decrease linearly with the increase of the regularity index. The above conclusions serve as a guide for revising the empirical formula.

Characterization of gapless topological quantum phase transition via magnetocaloric effect

It has attracted much attention on the interplay between topology and criticality in topological quantum systems, i.e., gapless topological quantum phase transition (TQPT) on critical lines. It is demonstrated that the magnetocaloric effect (MCE) is able to signal the gapless TQPT in an extended Kitaev chain, which is witnessed by the unusual critical behavior of joint effect of Grüneison ration (GR) and isothermal entropy change. We uncover the conventional TQPT between gapped phases showing high symmetry (HS) and non-HS critical points with self-duality, which is signaled by the finite value of GR as T → 0 and the largest inverse MCE with T-linear relation of isothermal entropy change. Two critical lines intersect at a multicritical point, at which there is a T−1 critical divergence of GR as well as T1/2 critical behavior of isothermal entropy change. It manifests a “weak” gapless TQPT on one critical line, demonstrated by the shifting zero-crossing of GR without the largest inverse MCE. On the other critical line, it shows a “strong” gapless TQPT, which is evidenced by the negative dip of GR together with the largest inverse MCE. Our work provides a novel thermodynamic perspective on gapless TQPT.

Verification of a novel stress path method by true-triaxial test

To verify the novel method of achieving a true-triaxial stress path with the pseudo-triaxial apparatus, a series of drained and undrained tests were carried out for the identical scheme with pseudo-triaxial apparatus and true-triaxial apparatus respectively. The differences between the two types of tests were quantified. The results show that the novel method effectively achieved the true-triaxial stress path by controlling the loading ratio of the pseudo-triaxial apparatus. The relationships of q − ε1 and η − εs measured by the two apparatuses had a higher similarity which decreases slightly with the b increase. When 0 ≤ b < 0.5, the slope of the critical state line measured by both apparatuses was almost identical. When 0.5 ≤ b ≤ 1, the slope of the critical state line measured by the novel method was slightly lower, but the biggest change was within 10% compared with the two Mohr–Coulomb criteria, the peak strength measured by the two apparatuses was distributed near the criteria, indicating the feasibility and rationality of the novel method. The tests show that the novel method greatly enriches the test range of pseudo-triaxial apparatus, which not only simplifies the process of soil 3D testing but also reduces the test cost.

A strategy to compute critical surfaces in highly asymmetrical ternary systems

This work shows that predicting, using a model, the topology and even the existence range of the critical behavior in an asymmetrical ternary system, is practically impossible without a systematic strategy to build through computations the ternary critical surface (T-CS). For this purpose, it is necessary to have robust calculation procedures to compute such surfaces. In this work, a calculation strategy to compute ternary critical lines (T-CLs) is developed. The computed critical surfaces for two different ternary systems are studied. In particular, the topology of these surfaces is analysed. First, a system with a relatively simple behavior is studied. Then, the strategies developed are tested for a system with complex behavior. In addition, the boundaries of a ternary critical surface (T-CS) are established, and it is described how to start the calculation of a T-CL (or a set of T-CLs) from a point on any of the established boundaries.

Field-controlled multicritical behavior and emergent universality in fully frustrated quantum magnets

Phase transitions in condensed matter are a source of exotic emergent properties. We study the fully frustrated bilayer Heisenberg antiferromagnet to demonstrate that an applied magnetic field creates a previously unknown emergent criticality. The quantum phase diagram contains four states with distinctly different symmetries, all but one pair separated by first-order transitions. We show by quantum Monte Carlo simulations that the thermal phase diagram is dominated by a wall of discontinuities extending between the dimer-triplet phases and the singlet-containing phases. This wall is terminated at finite temperatures by a critical line, which becomes multicritical where the Berezinskii-Kosterlitz-Thouless (BKT) transition of the dimer-triplet antiferromagnet and the thermal Ising transition of the singlet-triplet crystal phase also terminate. The combination of merging symmetries leads to a 4-state Potts universality not contained in the microscopic Hamiltonian, which we interpret within the Ashkin-Teller model. Our results represent a systematic step in understanding emergent phenomena in quantum magnetic materials, including the “Shastry-Sutherland compound” SrCu2(BO3)2.

Voltage stability improvement and power losses reduction through multiple grid contingency supports

A stable power system is a desirable state for the optimal performance and delivery of electricity to the end-users. This study evaluates the effectiveness of grid contingency support devices in power system stability enhancement. The new voltage stability pointer (NVSP) was employed to optimally infer the flexible alternating current transmission systems devices through N − 1 contingency ranking. In this research, the static synchronous compensator (STATCOM) was considered as a grid support device. The effectiveness of this technique was validated in R2018a MATLAB with the IEEE 30-bus system using different combinable contingency cases to ascertain the critical lines and vulnerable buses to outages. Based on the results obtained through the NVSP, buses 30, 26, and 29 were cited as STATCOM candidate buses for overall optimal grid performance. The results obtained from the simulation revealed that the total real power loss was reduced by 90.21%. Similarly, the voltage magnitude of the buses was significantly improved to a minimum of 1.00 p.u. after placement of STATCOMs. Further investigation on single STATCOM placement in the IEEE 30-bus system revealed that the highest level of voltage improvement, minimum level of voltage deviation and maximum active power loss reduction was achieved when the STATCOM was placed at bus 30. The overall assessment of the proposed technique yielded better results compared with other methods on the same test system.

RPS: Portfolio asset selection using graph based representation learning

Portfolio optimization is one of the essential fields of focus in finance. There has been an increasing demand for novel computational methods in this area to compute portfolios with better returns and lower risks in recent years. We present a novel computational method called Representation Portfolio Selection by redefining the distance matrix of financial assets using Representation Learning and Clustering algorithms for portfolio selection to increase diversification. RPS proposes a heuristic for getting closer to the optimal subset of assets. Using empirical results in this paper, we demonstrate that widely used portfolio optimization algorithms, such as Mean-Variance Optimization, Critical Line Algorithm, and Hierarchical Risk Parity can benefit from our asset subset selection.

Increasing the resilience of the Texas power grid against extreme storms by hardening critical lines

The Texas power grid on the Gulf Coast of the United States is frequently hit by tropical cyclones (TCs) causing widespread power outages, a risk that is expected to substantially increase under global warming. Here we introduce a new approach that combines a probabilistic line failure model with a network model of the Texas grid to simulate the spatio-temporal co-evolution of wind-induced failures of high-voltage transmission lines and the resulting cascading power outages from seven major historical TCs. The approach allows reproducing observed supply failures. In addition, compared to existing static approaches, it provides a notable advantage in identifying critical lines whose failure can trigger large supply shortages. We show that hardening only 1% of total lines can reduce the likelihood of the most destructive type of outage by a factor of between 5 and 20. The proposed modelling approach could represent a so far missing tool for identifying effective options to strengthen power grids against future TC strikes, even under limited knowledge.

Assessment of photovoltaic generation penetration effect on the maximum loadability of the system

This paper proposed a method to investigate the effect of increasing PV penetration on the voltage stability of an IEEE 14-bus test system considering maximum PV penetration and system loadability limit. The critical bus of the test system has been decided based on nose curve analysis. The solar PV system is deployed with the most critical bus of the system. The effect of increasing PV penetration on the improvement in the loading capacity of various power system components like transmission lines, transmission line transformers, and generators is investigated over the adopted test system. Based on solar PV penetration up to 100 MW, the maximum loadability limit of the IEEE 14-bus test system increases, as shown by the results. Bus 14 is found to be the most severe bus of the test system using the continuation power flow (CPF) method. However, in some cases, overloading situations develop after a certain limit of PV penetration in the power system. In this condition, the overloading of the power system equipment is improved by the use of a Static Synchronous Compensator (STATCOM) at bus number 14, a double circuit line in the critical line (9–14), and Static Synchronous Series Compensator (SSSC) in the most severe line (9–14) in the system. The maximum loadability of the system gets maximum enhanced from 4.0349 p.u. to 4.5602 p.u. under simultaneous use of solar PV generation, SSSC, and STATCOM at the most critical bus and in most severe line of the system. As evidence, the enhancement in maximum loadability of the system found using the proposed method has been also compared with the existing research. The maximum system loadability has been also enhanced under normal and (N-1) contingency conditions by the use of PV penetration in the system. PSAT/MATLAB software is used for simulation and maximum loadability has been investigated by continuation power flow (CPF) method.