Theoretical Results Research Articles

Asynchronous impulsive consensus of discrete-time nonlinear multi-agent systems with time-varying delays

This paper addresses the asynchronous impulsive consensus of discrete-time nonlinear multi-agent systems with time-varying delays. Moreover, leader-following relationship is considered for the presented multi-agent systems, in which cooperation and competition exist simultaneously. By using the linear matrix inequality (LMI) method and the stability theory for delayed discrete-time impulsive systems, a set of sufficient conditions for consensus are obtained to realize asynchronous exponential impulsive consensus with controllers acting at different time sequences for different agents. Mainly formulated by the topology matrices, impulsive intervals, and gain coefficients, these criteria are easily implemented and have lower energy consumption compared with traditional impulsive control methods. Finally, several numerical simulations are shown to display the effectiveness of the derived theoretical results.

Analysis of magnetic saturation effects in the squirrel cage induction generators

This work concerns an investigation on the analysis of the magnetic saturation effects in the three-phase squirrel cage induction generator which is considered as a main device in wind energy conversion systems. The magnetic saturation is considered as an important factor causing destructive effects on power qualities such as harmonics and distortion. Several approaches have been presented in the literature for the modeling of the electric machines considering magnetic saturation. The widely used and precise approach is the finite elements method which is particularly characterized by its high computational time. The novelty in this paper is that a state model has been developed for the healthy conditions of the three-phase squirrel cage induction generators considering the experimental variation of the magnetizing inductance in terms of the magnetizing current. Simulation and experimental tests are provided to extract some important signatures on stator voltages and currents. It will be deduced that the spectrum analysis of stator currents contains useful information on magnetic saturation. Experimental and theoretical results illustrate the consistency of this approach for the modeling and analysis of the squirrel cage induction generators considering the magnetic saturation.

Manipulating 2D Materials through Strain Engineering.

This review explores the growing interest in 2D layered materials, such as graphene, h-BN, transition metal dichalcogenides (TMDs), and black phosphorus (BP), with a specific focus on recent advances in strain engineering. Both experimental and theoretical results are delved into, highlighting the potential of strain to modulate physical properties, thereby enhancing device performance. Various strain engineering methods are summarized, and the impact of strain on the electrical, optical, magnetic, thermal, and valleytronic properties of 2D materials is thoroughly examined. Finally, the review concludes by addressing potential applications and challenges in utilizing strain engineering for functional devices, offering valuable insights for further research and applications in optoelectronics, thermionics, and spintronics.

Design & Development of Vortex Cooling System

Abstract: Possibilities for integration of vortex tube with automotive radiator for more effective cooling of automotive engine is the aim of the overview. An automotive radiator/heat exchanger is a device which helps maintain the working temperature of the engine. The vortex tube is a device which provides low temperature and high temperature output with pressure as an input. Because of its compact design and little maintenance requirements, it is very popular in heating and cooling processes. Despite its simple geometry, the mechanism that produces the temperature separation inside the tube is complicated. In addition, thermal and kinetic energy considerations have been used to explain temperature separation. There have also been plenty of numerical analyses that confirm earlier experiments. One fact remains, however. In this study, the past investigations of the design criteria of vortex tubes were overviewed and the detailed information was presented on the design of them. Vortex tubes were classified and the type of them was described. All criteria of vortex tubes were given in detail using experimental and theoretical results from the past until now.

Modeling and vibration analysis of an aero-engine dual-rotor-support-casing system with inter-shaft rub-impact

In order to reveal the nonlinear dynamics of dual-rotor-support-casing system, a numerical procedure is proposed using the finite element method and the component mode synthesis method. Especially, the casing system is subdivided into the casings, struts and housings, which are modeled by shell elements, beam elements and rigid regions with mass elements, respectively. Furthermore, the inter-shaft rub-impact, which may occur in the aero-engine because of imbalance and other faulty, is considered in the dynamic model as a nonlinear excitation. The modal analysis verified the validity of the dual-rotor-support-casing system model. The motion equations are established using the reduced-order model and solved by Newmark-β method with Newton-Raphson iteration. The results show that larger rubbing stiffness will cause the rubbing to enter a self-excited vibration state, and the rotational speed ratio will change the speed region where the self-excited vibration occurs. Finally, the experiment is performed based on a real dual-rotor aeroengine under inter-shaft rub-impact and the results are consistent with the theoretical results, which proves the effectiveness of dual-rotor-support-casing system dynamic model.

Crossover in densities of confined particles with finite range of interaction

We study a one-dimensional classical system of N particles confined within a harmonic trap. Interactions among these particles are dictated by a pairwise potential V(x), where x is the separation between two particles. Each particle can interact with a maximum of d neighbouring particles on either side (left or right), if available. By adjusting the parameter d, the system can be made nearest neighbour (d=1) to all-to-all (d=N−1) interacting. As suggested by prior studies, the equilibrium density profile of these particles is expected to undergo shape variations as d is changed. In this paper, we investigate this crossover by tuning the parameter f(=d/N) from 1 to 0 in the large N limit for two distinct choices of interaction potentials, V(x)=−|x| and V(x)=−log⁡(|x|) which correspond to 1d one-component plasma and the log-gas model, respectively. For both models, the system size scaling of the density profile for fixed f turns out to be the same as in their respective all-to-all case. However, the scaling function exhibits diverse shapes as f varies. We explicitly compute the average density profile for any f∈(0,1] in the 1d plasma model, while for the log-gas model, we provide approximate calculations for large (close to 1) and small (close to 0) f. Additionally, we present simulation results to numerically demonstrate the crossover and compare these findings with our theoretical results.

Vibration characteristics of blade-casing rubbing fault considering rotor–stator coupling

Blade-casing rubbing is a typical fault of aero-engine, but due to the complex structure of the equipment, it is still challenging to diagnose. This paper studies the characteristics of rubbing faults under rotor stator coupling. Firstly, a numerical model, which includes the rotor, bearings, and casing with blades, is constructed. Secondly, simulate the rubbing fault by setting the non-uniform initial gap between the blades and the casing, and the vibration response of the rotor and casing is obtained. Thirdly, combined with the test rig, the vibration characteristics under rubbing fault are verified. Finally, additional theoretical research is conducted on the vibration characteristics of the rotor, casing and blades under different degrees of rubbing fault. Theoretical and experimental results indicate that rubbing faults have different effects on the vibration of the rotor and stator: the rotational frequency amplitude of the rotor decreases while the frequency amplitude of the stator increases. As the fault degree increases, these phenomena become more significant. When rubbing faults occur, the harmonics near the system’s natural frequencies are more affected than the others. Moreover, rubbing faults can also cause the vibration of the rotor to be affected by the blade mode. The conclusions obtained in this paper can provide a reference for diagnosing rubbing faults in aero-engine.

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.

Global robust exponential synchronization of neutral-type interval Cohen–Grossberg neural networks with mixed time delays

Global robust exponential synchronization of neutral-type interval Cohen–Grossberg neural networks (NTICGNNs) with mixed time delays is analyzed in this paper. The system model, in which unrepresentable using vector-matrices, renders certain methods unsuitable for addressing issues within the vector-matrix framework. To address this limitation, a direct method based on system solutions is proposed, and sufficient conditions are provided to achieve global robust exponential synchronization of the considered NTICGNNs. This approach results in a global robust exponential synchronization criterion without the need to establish any Lyapunov-Krasovskii functionals. The applicability of the obtained synchronization conditions is validated using two numerical examples. Additionally, the obtained theoretical results have been applied to solve a quadratic programming problem and to encrypt and decrypt color images, demonstrating the practical application value of our research results. Notably, this study presents the first global robust exponential synchronization analysis for the considered NTICGNNs and proposes a novel approach grounded in system solutions.

Flow of an Oldroyd-B fluid in a slowly varying contraction: theoretical results for arbitrary values of Deborah number in the ultra-dilute limit

Flow of an Oldroyd-B fluid in a slowly varying contraction: theoretical results for arbitrary values of Deborah number in the ultra-dilute limit

Extending the hyper‐logistic model to the random setting: New theoretical results with real‐world applications

Extending the hyper‐logistic model to the random setting: New theoretical results with real‐world applications

A novel direct detection lidar compatible with software-defined radio

This paper proposes a novel direct detection lidar compatible with software-defined radio, which can effectively absorb the advantages of radio frequency technology. The radio frequency signal is firstly loaded onto the output light of the lidar through a fiber phase modulator and then demodulated from its backward reflected light through a combination of fiber Fabry-Perot interferometer and photodetector. The generation of the transmitting radio frequency signal and the sampling and processing of the receiving radio frequency signal are completed by a software-defined radio. Theoretically, it has been proven that the range and velocity of the target cause phase delay and Doppler frequency shift of the radio frequency signal loaded on the lidar, just like using the radio frequency signal to directly detect the target in radar. In the experiment, by programming the software-defined radio, the ranging and velocimetry algorithms of radar have been applied to this lidar. The theoretical and experimental results indicate that the lidar proposed in this paper has software definable characteristics. Through programming, different functions can be achieved, and in the future, more advanced algorithms of radar can be easily transplanted to further improve its performance.

Evaluation of SiL Testing Potential—Shifting from HiL by Identifying Compatible Requirements with vECUs

Due to the increasing complexity of vehicle software, it is becoming increasingly difficult to comprehensively test all requirements. This inevitably means that alternative test methods, e.g., simulation-based methods, must be used more frequently. However, the challenge involves identifying appropriate requirements that can be technically tested in a simulation environment initially. The present work is aimed at evaluation and optimization of the effectiveness of software-in-the-loop (SiL) simulations in the testing process of vehicle software. The focus is on supporting the testing process by shifting specific test cases from hardware-in-the-loop (HiL) test benches to SiL-based simulations. For this purpose, a systematic approach was developed to analyze and categorize requirements, enabling precise and efficient allocation of test cases. Furthermore, a detailed review and recommendation for improving the ProSTEP iViP standard for virtual electronic control units (vECU) was carried out. The developed matrix associates the defined requirement clusters with different classifications of vECUs, facilitating the identification of suitable test environment types for conducting specific test cases. By assigning test cases to appropriate vECU levels, the testing processes can be targeted and cost-optimized. Finally, the theoretical results were evaluated in an SiL simulation environment. It was observed that a significant part of the requirements could effectively be tested using a vECU. These findings confirmed the potential of SiL simulation environments to not only support, but also enhance, the testing process for vehicle software by providing a cost-effective and flexible complement to traditional HiL test benches.

On a Non-Convex Lagrange Optimal Control Problem

Abstract In this paper, we are concerned with an iterative differential inclusion governed by the time-dependent maximal monotone operator with perturbation. The approach to solve our problem is based on the Yosida approximation technique. The theoretical result is applied to prove an existence result for a Lagrange optimal control problem without assumptions concerning convexity.

Quantized Iterative Learning Bipartite Containment Tracking Control for Unknown Nonlinear Multi-agent Systems

This paper proposes a quantized model-free adaptive iterative learning control (MFAILC) algorithm to solve the bipartite containment tracking problem of unknown nonlinear multi-agent systems, where the interactions between agents include cooperation and antagonistic interactions. To design the controller, the agent’s dynamics is transformed into the linear data model based on the dynamic linearization method, and then a quantized MFAILC algorithm is established based on the quantized values of the relative output measurements. The designed controller only depends on the input and output data of the agent. We prove that under the quantized MFAILC algorithm, the multi-agent systems can achieve the bipartite containment, that is, the output trajectories of followers converge to the convex hull formed by the leaders’ trajectories and the leaders’ symmetric trajectories. Finally, we provide simulations to illustrate the effectiveness of our theoretical results.

Production of Xb via radiative transition of ϒ(10753)

We studied the radiative transitions between the ϒ(10753), the S−D mixed state of the ϒ(4S) and ϒ1(3D13), and the Xb, the heavy quark flavor symmetry counterpart of the X(3782) in the bottomonium sector. The radiative transition was assumed to occur through the intermediate bottom mesons, including P-wave B1(′) mesons as well as the S-wave B(*) ones. The consideration of the B1(′) mesons leads to the couplings to be in S-wave, and hence enhances the contributions of the intermediate meson loops. The radiative decay width for the ϒ(10753)→γXb is predicted to be order of 10 keV, corresponding to a branching fraction of 10−4. Based on the theoretical results, we strongly suggest to search for the Xb in the e+e−→γXb with Xb→ππχb1 near s=10.754 GeV, and it is hoped that the calculations here could be tested by the future Belle II experiments. Published by the American Physical Society 2024

Research on the performance of force measuring component − The key unit of vector thrust measuring system

The force measuring component (FMC) is the key structure of the thrust vector measuring device. The precise analysis of FMCs’ performance is crucial in elucidating the mechanism of vector force measurement and decoupling output data. The current testing technology solely utilizes FMCs, with no investigation into their mechanical properties. This paper presents an innovative and comprehensive mechanical analysis and modeling of FMC performance. The force transfer mechanism within the FMC is examined in each direction, and the structure is decomposed into its functional components, which are then treated as thin plate and beam structures. By applying principles of elastic mechanics, the local structure’s deformation function is analyzed. The complete deformation function for the FMC is established based on incorporating local and global deformation regulations. Finally, force-loading experiments were conducted, and deformation measurements were used to validate the FMC’s deformation function. The experimental results demonstrate a strong agreement between the theoretical calculations and experimental results. The maximum errors of axial and lateral deformation function is less than values of 4.77 % and 5.19 %, respectively, confirming that the theoretical function accurately characterizes the mechanical properties of the FMC.

Highly Efficient and Stable Organic Solar Cells Enabled by a Commercialized Simple Thieno[3,2-b]thiophene Additive.

Delicately manipulating nanomorphology is recognized as a vital and effective approach to enhancing the performance and stability of organic solar cells (OSCs). However, the complete removal of solvent additives with high boiling points is typically necessary to maintain the operational stability of the device. In this study, two commercially available organic intermediates, namely thieno[3,2-b]thiophene (TT) and 3,6-dibromothieno[3,2-b]thiophene (TTB) are introduced, as solid additives in OSCs. The theoretical simulations and experimental results indicate that TT and TTB may exhibit stronger intermolecular interactions with the acceptor Y6 and donor PM6, respectively. This suggests that the solid additives (SAs)can selectively intercalate between Y6 and PM6 molecules, thereby improving the packing order and crystallinity. As a result, the TT-treated PM6:Y6 system exhibits a favorable morphology, improved charge carrier mobility, and minimal charge recombination loss. These characteristics contribute to an impressive efficiency of 17.75%. Furthermore, the system demonstrates exceptional thermal stability (T80>2800h at 65°C) and outstanding photostability. The universal applicability of TT treatment is confirmed in OSCs employing D18:L8-BO, achieving a significantly higher PCE of 18.3%. These findings underscore the importance of using appropriate solid additives to optimize the blend morphology of OSCs, thereby improving photovoltaic performance and thermal stability.

Cloud in Blockchain Technologies

Cloud computing and blockchain technology have become essential ideas in the field of IT, providing new ways to handle data. Cloud computing offers internet-based access to computing resources like servers and storage, while blockchain guarantees the accountability and immutability of data transactions with its distributed ledger system. Combining these technologies can enhance organizations' capabilities in data security and management. Businesses can utilize scalable infrastructure on cloud platforms by implementing blockchain technology, eliminating the need for large investments in physical resources. This integration improves the ability to access blockchain networks, making interactions easier across different locations and devices. Additionally, it enhances data security and privacy measures by enabling encrypted connections and strong authentication methods in cloud-based blockchain systems. Yet, obstacles remain in guaranteeing the authenticity and protection of information kept in multi-cloud settings, requiring effective authentication measures. To tackle these difficulties, this article presents a method for verifying data integrity in multi-cloud storage using blockchain technology, utilizing the decentralized aspect of blockchain to improve transparency and security. The plan automates verification procedures through smart contracts and cryptographic hashing, allowing for integrity checks at both a general and specific level across multiple Cloud Service Providers (CSPs). The proposed scheme has its effectiveness and reliability validated through theoretical analysis and experimental results, highlighting its potential to improve the security and efficiency of multi-cloud storage systems. INDEX TERMS: Cloud Computing, Blockchain Technology, Data Integrity Verification, Multi-Cloud Storage, Smart Contracts, Cryptographic Hashing, Security, Transparency.

Lattice Engineering via Transition Metal Ions for Boosting Photoluminescence Quantum Yields of Lead-Free Layered Double Perovskite Nanocrystals.

Lead-free layered double perovskite nanocrystals (NCs), i.e., Cs4M(II)M(III)2Cl12, have recently attracted increasing attention for potential optoelectronic applications due to their low toxicity, direct bandgap nature, and high structural stability. However, the low photoluminescence quantum yield (PLQY, <1%) or even no observed emissions at room temperature have severely blocked the further development of this type of lead-free halide perovskites. Herein, two new layered perovskites, Cs4CoIn2Cl12 (CCoI) and Cs4ZnIn2Cl12 (CZnI), are successfully synthesized at the nanoscale based on previously reported Cs4CuIn2Cl12 (CCuI) NCs, by tuning the M(II) site with different transition metal ions for lattice tailoring. Benefiting from the formation of more self-trapped excitons (STEs) in the distorted lattices, CCoI and CZnI NCs exhibit significantly strengthened STE emissions toward white light compared to the case of almost non-emissive CCuI NCs, by achieving PLQYs of 4.3% and 11.4% respectively. The theoretical and experimental results hint that CCoI and CZnI NCs possess much lower lattice deformation energies than that of reference CCuI NCs, which are favorable for the recombination of as-formed STEs in a radiative way. This work proposes an effective strategy of lattice engineering to boost the photoluminescent properties of lead-free layered double perovskites for their future warm white light-emitting applications.