Numerical Results Research Articles

Empowering geological data analysis with specialized software GIS modules

This research is devoted to the development of a geographic information system (GIS) for the analysis of geological data. It presents two specialized software modules designed to solve complex geological problems related to potential progress to disturbed masses and magnetotelluric sounding. These modules are integrated into the QGIS environment, offering efficient data processing and analysis capabilities, contributing to a deeper understanding of geological structures. The study presents a mathematical model for the problem of magnetotelluric sounding (MTS) and the continuation of potentials towards the perturbed masses, demonstrating numerical results using the developed algorithm. To confirm the accuracy of the model, a comparative analysis was carried out with empirical data for various chemical elements, which showed high accuracy, especially at shallow depths, with an error rate of less than 2%. In addition, the study highlights the importance of powerful GIS for the analysis and interpretation of geological data, including geochemical, geophysical and remote sensing information. The advanced functionality of QGIS simplifies data processing and visualization, which makes it an invaluable tool for geologists and researchers.

A new analytical tool for the elastic/plastic buckling design of pressure vessels subjected to external pressure

This paper deals with the elastic/plastic buckling design of pressure vessels under external pressure loading. The objective is to build a simple analytical tool devoted to the elastic and elastoplastic buckling analysis of pressure equipments. This tool is aimed to provide the critical external pressure of cylindrical pressure vessels with ellipsoidal (or possibly hemispherical) heads. Depending on the geometry of the equipment and material parameters, the first buckling pressure may involve either the cylindrical shell or the closure ends, in the elastic or plastic range. The calculation tool will be thus based on a series of exact or approximate analytical solutions of the critical pressure of each part of the considered equipment. In this paper, the elementary shell structures involved in such pressure equipments are first individually examined. The fundamental critical pressures for each of them are recalled or introduced, both in elasticity and plasticity. The new solutions are validated against reference numerical results obtained through finite element computations. Then, approximate solutions of the critical pressure are derived for the same shells, taking account of specific boundary conditions (and not idealized ones, as before) due to the presence of the remaining part of the equipment. In the end, a VBA Excel software is developed. It is able to provide the mappings of the buckling mode type and the corresponding critical pressures for large ranges of geometric and material parameters in a very efficient way. These analytical solutions are finally confronted to numerical calculations performed on complete pressure equipments and they are shown to give quite reliable results. A discussion is also initiated on the use of such a program to update the current design rules in this scope of application.

Microwave plasma interaction in a printed transmission line for a power limiting application: from surface-wave-sustained to leaky-wave-sustained discharge

The coupling between a microwave signal and a plasma discharge in a suspended microstrip transmission line is analytically studied. Maxwell’s equations are solved in a 2D approximation to get the expressions of the electromagnetic field. The wave propagation in the guiding structure is first explored without plasma, and for several modes and frequencies. A unified characterization of the three different modes that can propagate at the interface between two dielectric media, namely the leaky waves, the pseudo-surface wave and the pure surface wave, is given in terms of of both wave vectors and electromagnetic field magnitude distribution. This analyze allow to conclude that the fundamental mode in this case is a pseudo-surface wave. Thereafter, we focus on the microwave propagation with a uniform plasma inside the guiding structure. In the non collisional limit, it appears that the plasma discharge is sustained by the so-called pure surface wave, whereas in the collisional limit, a leaky wave propagates along the plasma column. Finally, a non-uniform density profile is taken into account in the calculation. The numerical results obtained from the self-consistent simulation of the microwave-plasma coupling, in a previous work, are thus analyzed with the aid of the analytical formulas to identify the microwave coupling involved in our plasma-based microwave power limiter. The computed propagation constant from numerical data confirmed the type of coupling exhibited for a uniform electron density. Furthermore, we highlight the role of the dielectric slab, from which electromagnetic power transfer occurs into the plasma discharge.

Measuring absorbed energy in the human auditory system using finite element models: A comparison with experimental results.

There are different ways to analyze energy absorbance (EA) in the human auditory system. In previous research, we developed a complete finite element model (FEM) of the human auditory system. In this current work, the external auditory canal (EAC), middle ear, and inner ear (spiral cochlea, vestibule, and semi-circular canals) were modelled based on human temporal bone histological sections. Multiple acoustic, structure, and fluid-coupled analyses were conducted using the FEM to perform harmonic analyses in the 0.1-10 kHz range. Once the FEM had been validated with published experimental data, its numerical results were used to calculate the EA or energy reflected (ER) by the tympanic membrane. This EA was also measured in clinical audiology tests which were used as a diagnostic parameter. A mathematical approach was developed to calculate the EA and ER, with numerical and experimental results showing adequate correlation up to 1 kHz. Another published FEM had adapted its boundary conditions to replicate experimental results. Here, we recalculated those numerical results by applying the natural boundary conditions of human hearing and found that the results almost totally agreed with our FEM. This boundary problem is frequent and problematic in experimental hearing test protocols: the more invasive they are, the more the results are affected. One of the main objectives of using FEMs is to explore how the experimental test conditions influence the results. Further work will still be required to uncover the relationship between middle ear structures and EA to clarify how to best use FEMs. Moreover, the FEM boundary conditions must be more representative in future work to ensure their adequate interpretation.

Failure characteristics and fracture mechanism of overburden rock induced by mining: A case study in China

This study employs similar simulation testing and discrete element simulation coupling to analyze the failure and deformation processes of a model coal seam's roof. The caving area of the overburden rock is divided into three zones: the delamination fracture zone, broken fracture zone, and compaction zone. The caving and fracture zones' heights are approximately 110 m above the coal seam, with a maximum subsidence of 11 m. The delamination fracture zone's porosity range is between 0.2 and 0.3, while the remainder of the roof predominantly exhibits a porosity of less than 0.1. In addition, the numerical model's stress analysis revealed that the overburden rock's displacement zone forms an 'arch-beam' structure starting from 160 m, with the maximum and minimum stress values decreasing as the distance of advancement increases. In the stress beam interval of the overburden rock, the maximum value changes periodically as the advancement distance increases. Based on a comparative analysis between observable data from on-site work and numerical simulation results, the stress data from the numerical simulation are essentially consistent with the actual results detected on-site, indicating the validity of the numerical simulation results.

Efficiently linear and unconditionally energy-stable time-marching schemes with energy relaxation for the phase-field surfactant model

In this article, we consider consistent, efficient, and accurate numerical approximations for a recently developed Cahn–Hilliard type phase-field surfactant model enjoying the bounded-from-below condition of total energy. The phase-field surfactant model naturally satisfies the energy dissipation property in time. Based on this feature, we construct linearly decoupled and unconditionally energy-stable time-marching schemes based on an efficient variant of scalar auxiliary variable approach. To enhance the consistency of discrete modified energy and discrete original energy, a practical energy relaxation technique is adopted. We analytically proved the unique solvability and unconditional energy stability of the proposed schemes. In each time step, only two linear elliptic type equations with constants coefficients need to be solved and several algebraic operations need to be performed. Therefore, the proposed schemes are highly efficient and easy to implement. The space is discretized by the finite difference method and the linear multigrid algorithm is used to accelerate the convergence. The numerical results indicate that the proposed method not only has desired accuracy in time but also satisfies the energy dissipation law even if larger time steps are used. Furthermore, the surfactant laden spinodal decompositions and surfactant absorptions can be well simulated.

A modified J model for efficiently calculating the electromagnetic fields of ReBCO no-insulation pancake coils using an explicit–implicit hybrid algorithm

Rare-earth (Re)Ba2Cu3O7−x (ReBCO) no-insulation (NI) coil is widely concerned due to its excellent electromagnetic and thermal properties. However, the presence of the turn-to-turn shunts in NI coils leads to that complexity of numerical simulation is increased. In this paper, a modified J model is proposed and the corresponding explicit–implicit hybrid algorithm is designed to calculate NI coils. The numerical results are in good agreement with the experimental data and the circuit model. The homogenization model is also proposed to simulate the large-scale NI coils in the background magnets. The modified J model has good accuracy and fast calculation speed, which can also be used to solve electromagnetic fields of insulation coils efficiently.

Duality between Seiberg-Witten theory and black hole superradiance

The newly established Seiberg-Witten (SW)/Quasinormal Modes (QNM) correspondence offers an efficient analytical approach to calculate the QNM frequencies, which was only available numerically before. This is based on the fact that both sides are characterized by Heun-type equations. We find that a similar duality exists between Seiberg-Witten theory and black hole superradiance, since the latter can also be linked to confluent Heun equation after proper transformation. Then a dictionary is constructed, with the superradiance frequencies written in terms of gauge parameters. Further by instanton counting, and taking care of the boundary conditions through connection formula, the relating frequencies are obtained analytically, which show consistency with known numerical results.

Experimental and numerical investigation of punching and post-punching shear capacities of post-tensioned flat plate slab-column joints influenced by prestressing levels

Post-tensioned slab systems serve as an effective method to enhance the progressive collapse resistance of concrete flat plate structures by significantly improving the punching shear and post-punching capacities of their slab-column joints. While the existing research mainly focused on the punching shear behaviour of post-tensioned slab-column joints in small deformation stages, the post-punching behaviour in large deformations has been overlooked. This study aims to fill this research gap thorough experimental and numerical studies. Experimentally, four slab-column joints, including three post-tensioned specimens (with varied prestressing levels) and one specimen without tendons, were designed and tested. Detailed failure process and load-resisting mechanisms of the specimens at different deformation stages were discussed. The test results confirmed the efficiency of post-tensioning in improving the punching shear performance. Varying prestressing levels have influenced the development of punching shear capacity but did not affect the growth rate of load resistance in the initial post-punching stage. Numerically, validated finite element models were used to predict the post-punching capacities of the specimens. The numerical results indicated that post-tensioning helped increase post-punching capacities, but such an enhancement was independent of the prestressing levels. Additionally, the influence of the rupture strains of both tendons and reinforcement on the post-punching capacity was investigated through a parametric study.

Using a three-dimensional computational fluid dynamics model and an agglomerate model to investigate the effect of varying agglomerate parameters and output voltages on proton exchange membrane fuel cell performance

Modeling of proton exchange membrane (PEM) fuel cells is attracting more attention as fuel cell technology continues to develop. In this study, we considered a hybrid model that combines an agglomerate model based on the agglomeration of catalyst particles and the coverage-dependent kinetic equation of platinum oxide for ORR, and another 3D numerical model of a PEM fuel cell based on computational fluid dynamics (CFD). The obtained results from our developed models were validated with experimental results from literature. In fact, we investigated the effects of changing the agglomerate radius (Ragg), the ionomer volume fraction within the agglomerate (Yi,agg), the effective agglomerate surface area (Ai,agg), the distribution of the gases and the temperature on the cell performances.The results revealed that the cell performances are strongly influenced by changing Ragg and Yi,agg for medium and high current densities: The activation loss increases with increasing Ragg and decreasing Yi,agg. Also, Ai,agg increases with decreasing Ragg and increasing Yi,agg. In addition, the PEM fuel cell's power output is significantly enhanced when Ragg is decreased and Yi,agg is increased, the optimal power being obtained for values of Ragg=100nm and Yi,agg = 0.6. The numerical results also showed that decreasing the output voltage from 0.95V to 0.35V can accelerate the electrochemical reaction process.

Shear behavior of the fully prefabricated liftable connection for modular steel construction

Modular steel construction (MSC) is a novel structural system comprising of stacked modular units. It represents a type of green building with broad market prospects, which is aligned with industrialization and intellectualization trends. The shear behavior of the inter-module connection significantly impacts the lateral force resistance behavior of the MSC, which directly determines the load bearing capacity of the MSC. However, there are few studies on the shear behavior of the inter-module connection. A fully prefabricated liftable connection (FPLC) for MSC was proposed. The damage mechanism and design method of the FPLC under shear force were systematically investigated. Monotonic shear tests were conducted on six full-scale FPLC specimens. The failure mode, strain distribution, and load-bearing capacity of the FPLC under shear force were discussed. Subsequently, a refined finite element model (FEM) of the FPLC was established using the universal finite element analysis (FEA) software ABAQUS. The accuracy of the developed FEM was validated by comparing the experimental and numerical results. In addition, the development of the internal forces of the long stay bolts of the specimens was discussed to reveal the load-transfer mechanism of the FPLC. Finally, a series of prediction equations for the ultimate load-bearing capacity of the FPLC under a shear force were derived. The reliability of the proposed formulas was validated by comparing the theoretical and experimental results. The present research work will provide a comprehensive understanding of the shear behavior of the FPLC and corresponding design method, which is beneficial for the promotion of the MSC; limitations and future work are also briefly presented.

Flexural behavior of ECC reinforced RC beams under secondary load: Experimental, numerical simulation and theoretical analysis

The aim of this paper is to study the flexural behavior of reinforced concrete (RC) beams reinforced by engineered cementitious composite (ECC). The reinforcement effect of ECC on RC beam is studied by experiments, numerical simulation and theoretical analysis, considering the secondary load. Five beams were tested under static load, including two beams with ECC layers at the top and bottom (TBEB), two beams with ECC layers at the bottom (BEB) and one unreinforced beam. Different parameters in the test include reinforcement ratio, whether the top is equipped with ECC layer, and the thickness of the top ECC layer. The test data were used to validate the finite element model developed to simulate the bending response of the ECC layer reinforced beam. Then, a series of parameter studies were carried out to evaluate the effects of ECC layer thickness, reinforcement ratio and ECC elastic modulus on the reinforced beam. The experimental and numerical simulation results show that compared with other reinforced beams, TBEB equipped with 50 mm ECC layer at the top and bottom has better performance. Compared with the control beams, the ultimate bearing capacity is increased by 82.6 %, ductility and deformation capacity are increased by 2.38 times and 2.11 times, respectively. Finally, a calculation model for predicting the flexural capacity of TBEB is presented. The predicted flexural capacity is in good agreement with the experimental results.

Modeling the Nonmonotonic Immune Response in a Tumor–Immune System Interaction

Tumor–immune system interactions are very complicated, being highly nonlinear and not well understood. A large number of tumors can potentially weaken the immune system through various mechanisms such as secreting cytokines that suppress the immune response. In this paper, we propose a tumor–immune system interaction model with a nonmonotonic immune response function and adoptive cellular immunotherapy (ACI). The model has a tumor-free equilibrium and at most three tumor-presence equilibria (low, moderate and high ones). The stability of all equilibria is studied by analyzing their characteristic equations. The consideration of nonmonotonic immune response results in a series of bifurcations such as the saddle-node bifurcation, transcritical bifurcation, Hopf bifurcation and Bogdanov–Takens bifurcation. In addition, numerical simulation results show the coexistence of periodic orbits and homoclinic orbits. Interestingly, along with various bifurcations, we also found two bistable scenarios: the coexistence of a stable tumor-free as well as a high-tumor-presence equilibrium and the coexistence of a stable-low as well as a high-tumor-presence equilibrium, which can show symmetric and antisymmetric properties in a range of model parameters and initial cell concentrations. The new findings indicate that under ACI, patients can possibly reach either a stable tumor-free state or a low-tumor-presence state in the presence of nonmonotonic immune response once the immune system is activated.

Comprehensive Analysis of Blood Test Results Predicting Prognosis in Patients Undergoing Whole-brain Radiotherapy for Brain Metastases.

Blood tests, such as those included in the validated LabBM score (laboratory parameters in patients with brain metastases) predict survival after treatment of brain metastases. The model incorporates five test results [serum lactate dehydrogenase (LDH), C-reactive protein (CRP), albumin, platelets and hemoglobin]. However, many other abnormalities, albeit less well-studied, may be present in patients with metastatic cancer. Therefore, this study aimed to examine a broader range of blood tests. This retrospective analysis included 132 patients managed with primary whole-brain radiotherapy. Additional tests, such as liver enzymes, lymphopenia, hyponatremia, and others, were also conducted. Extracranial disease extent was also analyzed. According to forward conditional Cox regression analyses, blood tests (albumin, hemoglobin, lymphopenia, hyponatremia) in conjunction with the number of organs affected by extracranial metastases (at least two, such as liver and bones) provided the best prognostic model. Based on these parameters, at least four prognostic strata can be assigned (median survival between 4.6 and <1 months, p=0.0001). This initial pilot study in a limited number of patients suggests that numerous blood test results may contribute to further refinement of existing prognostic models, and provides justification for additional large-scale studies.

A novel term-structure-based Heston model for implied volatility surface

It remains a challenge for existing financial models to accurately capture the shapes of implied volatility (IV) of options with all maturities simultaneously. Inspired by Chen et al.’s empirical finding, ‘the shorter the option expiry, the higher the IV is’, we propose a novel and simple approach to solve this challenge, by introducing a term-structure-based correction (i.e. an exponential increase function of the options expiry) to the volatility of volatility (vol–vol) term of the classical Heston stochastic volatility model. We derive an approximate formula for the IV under the corrected model with the perturbation method and further apply the formula to predict the IVs of options written on the Shanghai Stock Exchange 50 ETF. Numerical experiments and empirical results show that the introduction of a term-structure-based correction function surely overcomes the deficiency of the classical Heston model in capturing the short-term IVs, thus improving notably its performance of IV forecasting.

Parsimonious Tensor Dimension Reduction

–Tensor data is emerging in many scientific applications, such as multi-tissue transcriptomics. In such cases, the covariates for each individual are no longer a vector. To apply traditional vector-based methods to this type of data, we need to either do the vectorization or analyze data marginally, which suffers a significant information loss. We propose a novel parsimonious tensor dimension reduction (pTDR) approach to directly link the response and tensor covariate through an unknown function g. In pTDR, the response variable, continuous or discrete, depends on K rank-one projections of the covariates, with the projections estimated via a sequential iterative dimension reduction algorithm. We further propose an asymptotic sequential statistical test to select the correct number of rank-one tensors. In contrast to the classic low-rank tensor regression, pTDR model is not restricted to the linear relationship between response and covariates. We apply pTDR to two modern genomic studies. We find that the gene expression of multiple tissues has a stronger association with aging and obesity than was apparent using previous approaches. Numerical results demonstrate the advantages of pTDR over competitors in terms of prediction accuracy and computing efficiency. Our software is publicly available on GitHub ( https://github.com/BioAlgs/pTDR).

An Edge-based Interface Tracking (EBIT) method for multiphase flows with phase change

In this paper, the Edge-Based Interface Tracking (EBIT) method is extended to simulate multiphase flows with phase change. As a novel Front-Tracking method, the EBIT method binds interfacial markers to the Eulerian grid to achieve automatic parallelization. To include phase change effects, the energy equation for each phase is solved, with the temperature boundary condition at the interface sharply imposed. When using collocated grids, the cell-centered velocity is approximately projected. This will lead to unphysical oscillations in the presence of phase change, as the velocity will be discontinuous across the interface. It is demonstrated that this issue can be addressed by using the ghost fluid method, in which the ghost velocity is set according to the jump condition, thereby removing the discontinuity. A series of benchmark tests are performed to validate the present method. It is shown that the numerical results agree very well with the theoretical solutions and the experimental results.

A Breakthrough Authentication Protocol for Fortifying IoT-Cloud Security

Abstract: Physical layer key generation, leveraging the reciprocity and randomness of wireless fading channels, has garnered significant research interest in recent years. While theoretical studies have demonstrated its potential to generate informationtheoretically secure keys, challenges remain in translating theory into practice. This paper provides an overview of the physical layer key generation process and discusses its practical challenges. Various passive and active attacks are analyzed and evaluated through numerical studies. A new key generation scheme using random probing signals and combining usergenerated randomness with channel randomness is introduced to counteract active attacks. Numerical results demonstrate that the proposed scheme achieves higher security strength than existing schemes using constant probing signals under active attacks. Secret-key generation relying on wireless channel reciprocity is an intriguing solution as it can be efficiently implemented at the physical layer of emerging wireless communication networks, while providing information-theoretic security guarantees. In this paper, we investigate and compare the secret-key capacity based on the sampling of the entire complex channel state information (CSI) or only its envelope, the received signal strength (RSS).

A novel collocation method with a coronavirus optimization algorithm for the optimal control of COVID-19: A case study of Wuhan, China

In this study, we develop a numerical optimization approach to address the challenge of optimal control in the spread of COVID-19. We evaluate the impact of various control strategies aimed at reducing the number of exposed and infectious individuals. Our novel approach employs Legendre wavelets, their derivative operational matrix, and a collocation method to transform the COVID-19 transmission optimal control model into a nonlinear programming (NLP) problem. To solve this problem, we employ a coronavirus optimization algorithm (COVIDOA) to determine the optimal control, state variables, and objective value. We investigate three control plans for this highly contagious disease, focusing on individual protection, rapid detection and treatment, detection with delay in treatment, and environmental viral dispersion as time-based control functions. These strategies are applied within an SEIR-type control model specific to COVID-19 in China, designed to mitigate disease spread. Lastly, we analyze the effects of various parameters within the COVID-19 spread model. Our numerical results highlight the significant impact of strategies that minimize the number of exposed and infectious individuals, particularly those related to rapid detection, detection delay, and environmental viral dispersion, in controlling and preventing the transmission of the COVID-19 virus.

High multiplicity of positive solutions in a superlinear problem of Moore–Nehari type

In this paper we consider a superlinear one-dimensional elliptic boundary value problem that generalizes the one studied by Moore and Nehari in Moore and Nehari (1959). Specifically, we deal with piecewise-constant weight functions in front of the nonlinearity with an arbitrary number κ≥1 of vanishing regions. We study, from an analytic and numerical point of view, the number of positive solutions, depending on the value of a parameter λ and on κ.Our main results are twofold. On the one hand, we study analytically the behavior of the solutions, as λ↓−∞, in the regions where the weight vanishes. Our result leads us to conjecture the existence of 2κ+1−1 solutions for sufficiently negative λ. On the other hand, we support such a conjecture with the results of numerical simulations which also shed light on the structure of the global bifurcation diagrams in λ and the profiles of positive solutions.Finally, we give additional numerical results suggesting that high multiplicity also holds true for a much larger class of weights, even arbitrarily close to situations where there is uniqueness of positive solutions.