Theoretical Analysis Research Articles

Modified calculation on shear stress of girder bridges with corrugated steel webs

The study examines the shear behaviors in girder bridges with corrugated steel webs (CSWs) considering different boundary constraints through theoretical analysis, experimental investigation, and numerical simulation. The accordion effect significantly amplifies shear deformation in CSWs at support locations. The substantial difference in shear stiffness between the CSWs and the concrete slabs constrains the shear deformation of CSWs, resulting in the generation of additional shear force within the CSWs. Therefore, the existing basic shear method is inaccurate for calculating shear stress in CSWs because it neglects this influencing factor. The study proposes an advanced formula for accurately predicting shear stresses near the supports of a cantilever prismatic girder bridge with CSWs by incorporating the additional shear forces induced by the shear deformation of CSWs. Theoretical analysis has revealed that the expression and magnitude of the additional shear force are correlated with the boundary conditions of the girder bridge. The study formulates expressions for the additional shear force induced by shear deformation in girder bridges with CSWs, considering various boundary conditions such as cantilever, simply supported, fixed-end, and continuous spans. It contributes to further enhancing the analytical method for calculating shear stress in prismatic girder bridges with CSWs, accommodating diverse support constraint conditions. The findings have practical implications for guiding the shear design of girder bridges with CSWs under various support systems.

Study on the Stability and Reasonable Width of Coal Pillars in “Three Soft” Coal Seams Based on a Physical Similarity Simulation Experiment

As the depth of coal seams increases and the demand for coal grows, the deformation and failure of roadways and coal pillars also intensify. To address the instability of roadways, it is crucial to study the appropriate dimensions for coal pillars. This paper focuses on the 1513 working face of the No. 5 coal seam at Anyang Coal Mine to address the issue of insufficient basis for determining coal pillar width. Through field observations and physical similarity simulations, this study examines the overlying strata failure patterns above coal pillars post-mining and the bearing structure formed by key layers. The relationship between these factors is analyzed using theoretical analysis and physical similarity simulations. A mechanical model of the coal pillar and the “hinged-hinged” overlying strata failure structure is established, analyzing the fracture characteristics of the overlying strata and the bearing structure of the coal pillar to determine the optimal coal pillar width under these conditions. The results indicate that when the coal pillar width is optimized from 25 m to 14 m, the overlying bearing layer is disrupted by the mining activities at the working face, with the lower key layer forming a “hinged” structure upon fracture. As mining progresses, the height of the overlying strata fractures gradually increases, causing the upper key layer to also fracture and form a “hinged-hinged” structure between the high and low bearing layers. According to the “three zones” development law, the height of overlying strata failure does not continue to increase indefinitely, and the coal pillar is affected by the “hinged-hinged” structure of the bearing strata. A mechanical model of the coal pillar bearing structure is established based on the fracture combination structure of the bearing strata. By calculating the load on the “hinged-hinged” structure of the overlying strata, the appropriate coal pillar width is determined to be 15 m. Theoretical calculations, physical similarity simulation experiments, and field applications show that without changing the support conditions, the deformation of the roadway is greater when the coal pillar is narrowed, compared to its original width. The maximum deformation, located 60 m ahead of the working face, increased by 41–42%, while deformation in other areas was relatively minor. This validates the reasonableness of the determined coal pillar width.

Plane SV-waves scattering by seawater convex surface topography and underlying lined tunnel in a saturated half-space

Analytical solutions of boundary-valued problems for aboveground topography and underground buried structures, especially for sites with overlying seawater, have always been challenging. Based on the region decomposition technique (RDT) and Hankel integral transform method (HITM), SV-waves scattering by the convex circular topography with seawater and underlying tunnel in a saturated half-space is solved. The primary problem is tackling additional scattered waves introduced by the water–soil interface and convex topography, while ensuring boundary conditions are all met. To this end, scattering wave potential functions in cylindrical coordinates are first transformed into the Hankel integral form in Cartesian coordinates. This greatly facilitates the straightforward application of free boundary conditions at the soil–seawater flat interface, rather than making a large circular arc approximate assumption, which, in turn, avoids the resultant accumulating errors. Secondly, scattering problem to be solved is mathematically and analytically formulated as solving a 5 × 5 linear equation system comprised of wave functions inside the convex topography and lining tunnel while satisfying all physical continuous boundary conditions. This is the main innovation and resulting consequence from the theoretical derivation process. Finally, validation of numerical examples between this paper, existing studies and theoretical analysis further demonstrates the reliability and general adaptability of solutions. Parametric studies of the incident SV waves are conducted to investigate the spatially varying seismic response. The effects of SV-waves incident angles and frequencies, tunnel burial depth, tunnel lining thickness, saturated soil porosity, and seawater depth are investigated and analyzed in detail. This study provides a feasible scheme of investigating the dynamic response of complex submarine sites, which is of great significance for both theoretical value and engineering purposes.

Mitigation of Parasitic and Drift Capacitance-Induced Nonlinear Current Responses for Stable and Sensitive Perovskite X-ray Detectors.

The development of perovskite direct X-ray detectors shows potential for advancing medical imaging and industrial inspection precision. To ensure the optimal energy conversion efficiency of X-rays for reducing radiation doses, it is necessary for perovskites with thicknesses reaching hundreds of micrometers or even several millimeters to be utilized. However, the nonlinear current response becomes uncertain with such high thicknesses. For instance, the prevailing theory regarding the rapid trapping and release of charges by shallow-level defects falls short in explaining the nonlinear current response observed in high-quality single-crystal samples. Moreover, a significant nonlinear current response can degrade the detection performance. Here, we elucidate peculiar parasitic and drift capacitance-induced nonlinear current responses in perovskites, which arise from bulk structural deficiencies and interface junction width variation in addition to shallow-level defects. Both theoretical analysis and experimental findings demonstrate the effective suppression of nonlinear current responses by establishing bulk heterojunctions and refining interface junctions. Consequently, we have successfully developed highly linear current-responsive detectors based on polycrystalline MAPbI3 thick films. Notably, these detectors achieve a record sensitivity of 2.3 × 104 μC·Gyair-1·cm-2 under 100 kVp X-ray irradiation with a low bias of 0.1 V/μm, enabling enduring and high-resolution X-ray imaging for high-density objects. Successful fabrication and testing of a 64 × 64-pixel flat-panel prototype detector affirm the widespread applicability of these strategies in rectifying nonlinear current responses in perovskite-based X-ray detectors.

A New Adaptive Sliding Mode Reaching Law: Theoretical Design and Simulation Analysis

AbstractIn the study (Wang et al. 2014), an adaptive reaching law is developed for sliding mode control (SMC). However, a potential issue arises when the sliding mode surface slides at the neighborhood of the origin, causing the adaptive gain in the mentioned scheme to chatter repeatedly. This results in input command chattering and has a negative impact on the stability of the system. In order to address this problem caused by the adaptive gain and switching function in SMC, and to further improve convergence performance, a new adaptive reaching law is proposed. This proposed reaching law improves upon the previous adaptive gain and ensures stable operation as the new adaptive gain converges to a small neighborhood of the origin. This improvement prevents chattering and guarantees that the tracking error of the system converges within a finite time. Finally, comparative simulation experiments are conducted to demonstrate the effectiveness and superiority of the proposed reaching law.

Algorithms for Densest Subgraphs of Vertex-Weighted Graphs

Finding the densest subgraph has tremendous potential in computer vision and social network research, among other domains. In computer vision, it can demonstrate essential structures, and in social network research, it aids in identifying closely associated communities. The densest subgraph problem is finding a subgraph with maximum mean density. However, most densest subgraph-finding algorithms are based on edge-weighted graphs, where edge weights can only represent a single value dimension, whereas practical applications involve multiple dimensions. To resolve the challenge, we propose two algorithms for resolving the densest subgraph problem in a vertex-weighted graph. First, we present an exact algorithm that builds upon Goldberg’s original algorithm. Through theoretical exploration and analysis, we rigorously verify our proposed algorithm’s correctness and confirm that it can efficiently run in polynomial time O(n(n + m)log2n) is its temporal complexity. Our approach can be applied to identify closely related subgroups demonstrating the maximum average density in real-life situations. Additionally, we consistently offer an approximation algorithm that guarantees an accurate approximation ratio of 2. In conclusion, our contributions enrich theoretical foundations for addressing the densest subgraph problem.

Tunable topological edge state in plasma photonic crystals

Abstract In this work, we found a kind of edge state located at the interface between plasma photonic crystals (PPCs) and traditional photonic crystals, which depends on the property of the photonic band gap rather than the surface defect. Simulation and theoretical analysis show that by adjusting plasma density, we can change the topological characteristics of the photonic bandgap of PPCs, making it different from the photonic bandgap of traditional PCs, and thus excite or close the topological edge states. We further discussed the influence of plasma parameters on edge state characteristics, and the results showed that as the plasma density increased, the first photonic band gap (PBG) of the PPCs would be closed and then be reopened, resulting in band inversion and a change in the PBG properties of the PPCs. We can control the generation of edge states through plasma, and adjust the frequency and strength of the edge states. After the appearance of edge states, as the plasma density further increases, the first PBG of the PPCs will shift towards high frequencies and deepen. The frequency of edge states will shift towards higher frequencies, and their strength will also increase. We increased the first PBG depth of the PPCs by increasing the number of arrays, and found that when the number of the PPCs arrays increased, only the intensity of edge states would increase while the frequency remained unchanged. Therefore, flexible adjustment of edge states frequency and intensity can be achieved through the parameters of plasma density and array quantity. Our work demonstrates the properties of non-trivial edge states in plasma photonic crystals, which we believe can provide some guidance for applications based on edge states.

Time‐varying output group formation‐containment tracking control for heterogeneous multi‐agent system

AbstractThe time‐varying output group formation‐containment tracking (TVOGFCT) problem of discrete‐time heterogeneous multi‐agent system (MAS) is investigated in this paper. Assuming the MAS consists of multiple tracking leaders, formation leaders, and followers, and all the agents are divided into several groups. Firstly, to estimate the convex combination of tracking leaders in the same group, the distributed observers are designed for the formation leaders, and the observer‐based formation tracking protocols are also presented to make formation leaders realize the desired time‐varying group formation while tracking the convex combination of tracking leaders. Then, two types of observers are proposed to estimate the convex combination of tracking information and formation functions, based on which the containment tracking protocols are designed for the followers of each group. By using output regulation theory and Lyapunov theory, it is illustrated that the designed protocols can make the MAS realize TVOGFCT. Finally, the simulation results prove the correctness of the theoretical analysis.

Stress path-based compressive strength model of FRP-confined recycled aggregate concrete

The compressive strength model of fibre-reinforced polymer (FRP) confined recycled aggregate concrete (RAC) is important in practical engineering designs. The existing research has showed that the compressive strength of FRP-confined RAC can be predicted by the models for FRP confined natural aggregate concrete (NAC). However the accuracy of existing compressive strength models for FRP-confined NAC vary greatly because of the unclear understanding of the confinement mechanisms. Previous research has shown that the axial stress of confined concrete tends to be path-dependent. In this study, a confining stress path-based compressive strength model of FRP-confined RAC is proposed based on theoretical analyses of the confining stress path of FRP-confined RAC. In the proposed model, an effect index is determined to express the influence of confining stress path on the compressive strength. The relationship between the effect index and confinement ratio and that between lateral stress dominant index and confinement ratio are obtained. The proposed model is verified by comparison with previous experimental test results and those predicted by existing representative models. It is found that the compressive strength of FRP-confined RAC is path-dependent for small confinement ratios (less than 0.43) and path-independent for large confinement ratios (larger than 0.43).

A fair and scalable watermarking scheme for the digital content trading industry

The booming Internet economy and generative artificial intelligence have driven the rapid growth of the digital content trading industry, creating an urgent need for the fair protection of the rights of both buyers and sellers. To meet this need, a technique known as buyer–seller watermarking has emerged. Despite its existence, the majority of existing buyer–seller watermarking schemes adopt the owner-side embedding mode, which results in poor scalability. While a handful of schemes adopt the client-side embedding mode to enhance scalability, they either require the deep involvement of a trusted third party or fall short of ensuring complete fairness due to the unresolved unbinding problem. To address these challenges, this paper proposes a fair and scalable watermarking scheme for digital content transactions based on proxy re-encryption and digital signatures. For one thing, this scheme solves the unbinding problem and ensures complete fair protection of the rights of both buyers and sellers. For another, it adopts the client-side embedding mode and has good scalability. Additionally, it eliminates the need for a trusted third party. Finally, theoretical analysis and experiments demonstrate that the proposed scheme achieves the intended design goals and possesses superior efficiency advantages.

Contrastive Unsupervised Representation Learning With Optimize-Selected Training Samples.

Contrastive unsupervised representation learning (CURL) is a technique that seeks to learn feature sets from unlabeled data. It has found widespread and successful application in unsupervised feature learning, with the design of positive and negative pairs serving as the type of data samples. While CURL has seen empirical successes in recent years, there is still room for improvement in terms of the pair data generation process. This includes tasks such as combining and re-filtering samples, or implementing transformations among positive/negative pairs. We refer to this as the sample selection process. In this article, we introduce an optimized pair-data sample selection method for CURL. This method efficiently ensures that the two types of sampled data (similar pair and dissimilar pair) do not belong to the same class. We provide a theoretical analysis to demonstrate why our proposed method enhances learning performance by analyzing its error probability. Furthermore, we extend our proof into PAC-Bayes generalization to illustrate how our method tightens the bounds provided in previous literature. Our numerical experiments on text/image datasets show that our method achieves competitive accuracy with good generalization bounds.

Dynamic analysis of a delayed pest-natural enemy model: Triple effects of non-monotonic functional response, additional food supply and habitat complexity

Considering the food diversity of natural enemy species and the habitat complexity of prey populations, a pest-natural enemy model with non-monotonic functional response is proposed for biological management of Bemisia tabaci. The dynamic characteristics of the proposed model are analyzed. In addition, considering that the conversion from prey to predator has a certain time lag rather than instantaneous, a time delay is introduced into this model, and it is shown that the Hopf bifurcation occurs at the interior equilibrium when the time delay is used as the bifurcation parameter. Furthermore, the values of the parameters that determine the direction of the Hopf bifurcation as well as the stability of the periodic solution are calculated. In order to illustrate the theoretical analysis results, numerical simulations and validation are carried out to demonstrate the effects of non-monotonic functional response, additional food supply and habitat complexity.

Dynamic performance evaluation of a magnetorheological damper-based sting support in wind tunnel tests

The sting support faces an issue of being prone to resonance due to its low-damping characteristics, which will compromise the accuracy of test data in wind tunnel experiments. Magnetorheological damper (MRD)-based tail support (MRSS) features varying stiffness and damping abilities, enabling it to suppress the vibration with random, time-variation characteristics in a self-adaptive way, and it also exhibits excellent fail–safe properties. This work aims to validate its controllability and fail–safe property in a wind tunnel environment. First, the natural frequency, root mean square (RMS), and power spectral density (PSD) of the designed MRSS’ response for random excitation were theoretically analyzed. Then, wind tunnel experiments were conducted to test the response under different attack angles, wind speeds, and test currents. Subsequently, the controllability and fail–safe property were demonstrated by analyzing the aircraft model response. Also, the variable stiffness and damping properties of MRD behind the observed phenomena were revealed based on the theoretical analysis. Results demonstrate that as the input current increases and the MRD’s stiffness continues to increase, the damping initially increases and then decreases. Increasing wind speed leads to a decrease in the MRD’s stiffness. Additionally, approximately 50% reduction in RMS and a multi-modal response attenuation was achieved.

The Oliver Twist: Why young adults watch Last Week Tonight with John Oliver

ABSTRACT Motivations matter because they affect cognitive processes, which in turn impact any effects that satire might have upon viewers. Therefore, a better understanding of motivations add nuance to future research and generates suggestions on how to create engaging news narratives for a twenty-first century audience. This paper investigates why young adults watch the popular journalistic satire show Last Week Tonight with John Oliver. Through semi-structured interviews with young adults (N = 11), using theoretical thematic analysis, a framework of 11 motivations for consuming satire was constructed. The results of this study carry four implications: (1) entertainment and information are interdependent, (2) information is made up of learning and understanding, (3) two new motivations were discovered: inspiration and host, and (4) young adults desire authenticity.

Experimental investigation and theoretical modeling of copper corrosion inhibition by Urginea maritima essential oil

Corrosion inhibition is essential for preserving metallic materials in various industrial applications. This study aims to assess the inhibition performance of Urginea maritima essential oil (HEUM) in mitigating copper corrosion within a 0.5 M sulfuric acid environment. The experimental investigation examined the inhibition properties of the essential oil using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization studies (PDP) and surface analysis by scanning electron microscopy (SEM). In addition, theoretical studies have been carried out using density functional theory (DFT) to further elucidate corrosion inhibition mechanisms. The findings from both experimental and theoretical analyses suggest a notable reduction in corrosion rates with the essential oil, highlighting its promising efficacy as an inhibitor, and the inhibitory effect of HEUM essential oil can be attributed to a synergistic effect between its various components. Furthermore, thermal stability studies demonstrate sustained inhibitory action over a range of temperatures. These results demonstrate the high potential of HEUM as a natural and eco-friendly corrosion inhibitor, warranting further exploration of practical applications in corrosion control strategies.

The use of big data analytics for human resource management in an organization

Aim. To examine the application of big data in the field of human resource management and in organizational network analysis as a methodology to study the patterns of employee interaction within a formal organizational structure to improve the effectiveness of the human resource management system.Objectives. Theoretical analysis of existing methodologies for evaluating data on human resources of an organization to provide new opportunities for enterprise transformation; identification of hidden information on human resources and its use for internal staff development, retention and training; study of the possibilities of using organizational network analysis (ONA) to improve the effectiveness of human resource management.Methods. The authors used system and logical approaches, general scientific methods (analysis, synthesis), methods of comparative and economic analysis, analytical processing of information, graphical presentation of information.Results. The sources of big data are analyzed, the main indicators characterizing the state of personnel and allowing to forecast its development, dynamics of preservation of human resources in the organization, its training are allocated. The directions of using organizational network analysis in the personnel management system are proposed.Conclusions. The identified potential advantages of using organizational network analysis in the analytics of data on human resources in the organization will contribute to the reduction of staff turnover, optimization of staff structure, improvement of experience and knowledge sharing within the organization. This, according to the author’s position, will lead the enterprise to a positive economic effect and open new opportunities for its transformation

Flexural behavior of laminated H-beams in modular constructions: Numerical and analytical studies

Modular steel construction (MSC) has become an important development direction of the construction industry thanks to the faster construction speed and recyclability. The laminated steel beam is one of the key structure characteristics of MSC, which can enhance the structural integrity by strengthening the interaction between the adjacent beams in vertically stacked modules. In this study, numerical and analytical studies were carried out to explore the flexural behavior and design method of the laminated H-beams in MSC. Firstly, finite element models were established and verified based on the previous experimental study on flexural behavior of the laminated square steel tube beams and laminated channel steel beams. Afterwards, finite element analysis was conducted on flexural behavior of the laminated H-beams with different connecting bolts. The results showed that the flexural capacity and stiffnesses of the laminated H-beams were significantly improved by increasing the number of the connecting bolts in the bending-shear sector. The flexural behavior of the laminated H-beams was discussed including the failure mode, load-deflection curves and slippage of the superimposed surface to reveal the co-bending mechanism. In addition, parametric analysis was performed to reveal the influence of the position, number and diameter of the connecting bolts on flexural behavior of the laminated H-beams. Finally, a theoretical model on flexural capacity of the laminated H-beams was developed to determine the neutral axis and derive the flexural capacity of the laminated H-beams. The calculation formulas were verified to be reliable by comparing the theoretical analysis results with the numerical ones. The present study is beneficial to consummating the mechanical behavior and design method of MSC.

Interaction of Hermite–Gaussian Beams with a Macroscopic Atomic Target

AbstractA theoretical analysis is presented on the photoexcitation of a macroscopic atomic target by a Hermite–Gaussian (HG) beam within the framework of density matrix theory. Special emphasis is paid to the influence of the incoming HG mode on the population of an excited state and the emitted fluorescence radiation. In particular, a general expression for the alignment parameter of the excited state is derived, which depends on the beam parameters of the HG mode. Although the developed theory can be applied to any atomic system, here the electric dipole transition in neutral sodium atoms is investigated when driven by three , and modes. For this optical (valence‐shell) excitation, it is demonstrated that the population of the excited state is sensitive to the beam waist and the mode index of the HG beam. Furthermore, the influence of beam parameters on the angular distribution and linear polarization of the emitted fluorescence radiation is discussed.

Spectroscopy and luminescence dynamic of Ce3+ and Sm3+ ions in Na3Y(BO3)2

Ce3+, Sm3+ singly-doped and Ce3+-Sm3+ co-doped sodium yttrium borate Na3Y(BO3)2 phosphors are prepared using a high temperature solid-state reaction route, in order to investigate their spectroscopic properties, luminescence dynamic and energy transfer mechanisms. The weak electron-vibrational interaction (EVI) between Ce3+ ions and their surroundings is demonstrated according to measured spectra and theoretical analysis. The mechanism of the Ce3+ → Sm3+ energy transfer in the host is investigated via luminescence dynamic models. In addition, the potential application of Ce3+-Sm3+ co-doped Na3Y(BO3)2 phosphors in the optical anti-counterfeiting is demonstrated according to the luminescence regulation of excitation wavelength response.

Examining the Integration of Responsible AI Principles in Social Media Marketing for Digital Health: A Theoretical Analysis

Examining the Integration of Responsible AI Principles in Social Media Marketing for Digital Health: A Theoretical Analysis