Break Research Articles

Preparation and Modification of Flexible Polyurethane Foam for Effective Flame Resistance and Sound Absorption

Polyurethane foam as an important sound absorption material is limited by the poor flame resistances in building field, but the modifications of flame resistances tend to have adverse effects on the sound absorption performance. Herein, dibutyltin dilaurate and triethylenediamine are used simultaneously as catalysts, and four new types of flame retardant polyether polyols (FPMPO) are synthesized and combined with modified expanded graphite (PEG) to prepare the flame resistance flexible polyurethane foam (FFPUF) by one-step method. The results show that the combination of the two catalysts can control the cell structure of FFPUF availably for sound absorption. The FPMPO have little negative influence on the cell morphology and the sound absorption performance of FFPUF, but the increase of flame resistances is finite due to the limited amount of FPMPO. In order to improve the flame retardant properties further, the FPMPO and the PEG are combined in the modification. Benefitting by the effective control structure and the modification with composite flame retardant, the FFPUF shows excellent sound absorption and flame retardant properties. The LOI value of FFPUF is 33.4 and the vertical burning level reaches V-0, and the average sound absorption coefficient maintains 0.68 in the 800-6300 Hz range.

Unified Fuzzy Control of High-Order Nonlinear Systems With Multitype State Constraints.

This article presents a unified adaptive fuzzy control approach for high-order nonlinear systems (HONSs) with multitype state constraints. Existing methods always require the upper and lower constraint boundaries are strictly positive and negative functions (or constants), respectively, which is often inconsistent with the actual constraints. In this article, "multitype state constraint" means that the upper and lower constraint boundaries include multiple types, such as both being strictly positive (or negative), sometime be positive or negative, and so on (cases ①-⑥). By designing a unified mapping function (UMF), the multitype state constraints are processed under removal the feasibility conditions (FCs). Furthermore, a technical design makes the proposed method also applicable to unconstrained HONSs without changing the control structure. By means of a fuzzy-logic system (FLS) and fixed-time stability theory (FTST), the proposed algorithm can ensure that the tracking error converges to a zero-centered neighborhood within a fixed time, and the singularity which often appears in the existing fixed-time control (FTC) methods of HONSs is effectively avoided. Simulation results demonstrate the scheme developed.

Wave Energy Optimal Control Structure With Second-Order Sliding Mode Tracking: Hardware-in-the-Loop Assessment

Wave Energy Optimal Control Structure With Second-Order Sliding Mode Tracking: Hardware-in-the-Loop Assessment

Structural color tunable intelligent mid-infrared thermal control emitter

This work proposes a colored intelligent thermal control emitter characterized by adjustable structural color development with a reflection spectrum in the visible light range and intelligent thermal control with temperature switching in the mid infrared wavelength band. In the beginning, we investigate an intelligent thermal control emitter based on a multilayer membrane formed by the phase change material vanadium dioxide, metal material Ag, and dielectric materials Ge and ZnS. By incorporating the thermochromic material vanadium dioxide, the structure exhibits a high emissivity of εH = 0.85 in the range of 3–13 μm wavelength when in the high temperature metallic state, enabling efficient heat radiation. In the low temperature dielectric state, the structure only has a low emission capacity of εL = 0.07, reducing energy loss. Our results demonstrate that the structure achieves excellent emission regulation ability (Δε = 0.78) through the thermal radiation modulation from high to low temperature, maintaining effective thermal control. Furthermore, the thermal control emitter exhibits selective emission of peak wavelength due to destructive interference and shows a certain independence on polarization and incidence angle. Additionally, the integration of structural color adjustment capability enhances the visual aesthetics of the human experience. The proposed colored intelligent thermal control structure has significant potential for development in aesthetic items such as colored architecture and energy-efficient materials.

Grid Forming Converter Control System Synthesis: A Static Output Feedback Approach

This paper proposes an effective control synthesis strategy to stabilize grid forming converters in the presence of disturbances. The conventional control system for a grid forming converter is based on paralleled and cascaded proportional‐integral (PI) controllers, which are widely used in the industry due to their simplicity and reliability. However, the sequential adjustment of PI gains in different control loops, without consideration of dynamic interconnections limits their performance and capability. To address this limitation, the present paper introduces a control design method based on static output feedback theory. The proposed control scheme reduces the dynamic control design problem to an effective gain scheduling problem. In the proposed methodology, without removing the existing practical control structure, its dynamic parts are moved to the open‐loop system, and simultaneous scheduling of all remaining control gains is achieved during one control design process. MATLAB simulations were conducted to evaluate the performance of the designed control system, and compare it with the conventional control one in terms of step response characteristics. The results demonstrate the superiority of the proposed controller, ensuring system stability and exhibiting improved performance. The proposed control framework provides several advantages, including keeping stability in various disturbance conditions, simultaneous tuning of all control parameters, and no need to change the existing simple control structure. © 2024 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Novel dynamic control structure of reactive distillation process for isopropanol production via transesterification

Due to the complicated interaction between reaction and separation in a column, it was inherently challenging to design a control structure for the reaction distillation process. In this research, the control structures of the hybrid reactive distillation process combining pressure-swing distillation (RDC-HDC) and its thermal coupling (RDWC-HDC) processes, were explored for producing isopropanol (IPA) by isopropyl acetate (IPAC) with methanol (MeOH) transesterification. The control performances of only temperature control and temperature difference control schemes for RDC-HDC process were first investigated. The research results displayed that double temperature control (CS3) and temperature difference control schemes (CS4–1, CS4–2 and CS5) for the RDC-HDC process could shorten the maximum transient deviation, amplitude of oscillations and setting time in face with ±20% throughout and ±5% feed composition disturbances. To further improve control characteristics and make control structures concise, a novel control strategy (CS6) by a proportional controller adjusted by reverse action of an IPAC component controller in 34 trays for keeping IPAC composition at a certain range in the RDC-HDC process was developed based on the closed loop analysis before and after disturbance. The application of the innovative control structures (CST4) to the RDWC-HDC process was equally feasible in face of ±10% throughout and ±5% feed composition disturbances. The analysis of integral of squared error (ISE) indicated that a novel control strategy (CS6 and CST4) had better robustness and dynamic performance. These studies contributed to the development of controllability for hybrid reactive distillation processes to produce chemicals for reaction and separation.

Cascade NMPC-PID control strategy of active heave compensation system for ship-mounted offshore crane

In this paper, the problem associated with active heave motion compensation during heavy-lift operations performed by ship-mounted offshore cranes beneath rough marine environment is investigated. To effectively decouple the correlated motion of the suspended payload from the support vessel via the secondary regulated active heave compensation (SRAHC) system, a novel hierarchical control strategy is proposed by integrating a cascade control structure with an adaptive robust control scheme that incorporates a vertical motion forecast algorithm based on autoregressive integrated moving average (ARIMA) model, a conventional proportional-integral-derivative (PID) framework, and a nonlinear model predictive control (NMPC) method. The introduction of the cascade structure is motivated by its prompt error response against control lag and efficient system order reduction for computational burden alleviation, which forms a crucial foundation for the NMPC-based real-time regulation of PID gains, ensuring optimal evolution of the SRAHC system while improving its practical feasibility. Furthermore, the enhancements in heave compensation and trajectory tracking performance, noise resistance, constraint satisfaction, and engineering application potential of the proposal are demonstrated through a thorough comparative analysis conducted in a practical co-simulation research system.

International legal regulation of reforming the Armed Forces of Ukraine to NATO standards. studying the experience of command groups' activities in the armies of NATO member states and partner countries

The paper investigates the concept of mission command within the framework of military management, focusing on its application in modern military operations. Mission command, characterized by centralized intent and decentralized execution, is examined in terms of its origins, principles, and effectiveness in enhancing speed and initiative in military actions. The author conducts a comprehensive analysis of how mission command has been utilized by various military forces worldwide, assessing its alignment with contemporary strategic concepts and its contribution to achieving strategic objectives. Special attention is paid to its relevance and applicability in the context of the Ukrainian Armed Forces reform, particularly in enhancing command and control structures. The research highlights mission command as a vital component of effective military leadership, facilitating adaptability and responsiveness in complex operational environments. The findings underscore the importance of integrating mission command principles into modern military management systems to optimize decision-making processes and achieve mission success. Overall, the study provides valuable insights into the practical implementation and impact of mission command on military operations, offering recommendations for its further development and refinement within the Ukrainian Armed Forces and beyond.

Precise control of platinum coordination environment on fullerene-derived catalysts for oxygen reduction reaction

The interaction between catalysts and supports is recognized as a crucial factor influencing catalytic activity and stability. However, the carbon materials, which have been widely employed as the support at present, encounter challenges including intricate composition and the difficulty of precise control. In this study, the fullerene-derived carbon materials serve as support to electrocatalysts with low platinum. Fullerene-based materials, as the only carbon material with a well-defined molecular structure, have a controllable active site structure, which can provide a reaction model for studying metal-support interactions. Four kinds of fullerene-derived catalysts such as Pt/fullerene, Pt/nitrogen-doped fullerene, Pt/sulfur-doped fullerene, and Pt/phosphorus-doped fullerene, were synthesized. Once the coordination environment of the Pt particles was controlled, thus their catalytic performance was modulated. Despite a platinum loading of only 4.2%, Pt/N-fullerene demonstrates superior oxygen reduction activity and stability compared to commercial Pt/C (20%). Density functional theory calculations show that the introduction of heteroatoms can change the surface charge distribution of fullerenes, in which N-fullerene has a more negative electrostatic potential and can effectively anchor Pt. This research establishes a foundation for understanding the catalysts-support interaction and further precise control of the coordination environment of Pt. This provides new insights for designing efficient ORR catalysts.

Crucial Breakthrough of BODIPY‐Based NIR‐II Fluorescent Emitters for Advanced Biomedical Theranostics

AbstractFluorescence imaging in the second near‐infrared window (NIR‐II, 1000–1700 nm) has aroused immense attention for biomedical applications, offering exceptional advantages such as ultra‐low photon scattering and increased tissue penetration. Among the NIR‐II‐emitted organic dyes, Boron dipyrromethene (BODIPY), has emerged as a noteworthy candidate. BODIPY, distinguished by its controllable molecular structure and optical properties, outstanding fluorescence quantum yields, high molar absorption coefficients, and remarkable chemical stability, has undergone comprehensive investigation and extensive exploration within the realm of biological theranostics. This work aims to provide a comprehensive summary of the advancements in the development and design strategies of NIR‐II BODIPY fluorophores tailored for advanced biological phototheranostics. Initially, the work elucidates several representative and controllable strategies, concluding the electron‐programming strategy, extension of the conjugated backbone, J‐aggregation strategy, and strategic establishment of activatable fluorophores, which enhance the NIR‐II fluorescence of BODIPY skeletons. Subsequently, developments in NIR‐II fluorescent BODIPY‐based nanoplatforms for biological applications are intricately elaborated. In conclusion, this work outlines future efforts and directions for refining NIR‐II BODIPY to meet evolving clinical demands. It is anticipated that this contribution may provide a feasible reference for the strategic design of organic NIR‐II fluorophores, thereby advancing their potential in future clinical practices.

An optimal hybrid quadcopter control technique with MPC-based backstepping

Quadcopter unmanned aerial vehicle is a multivariable, coupled, unstable, and underactuated system with inherent nonlinearity. It is gaining popularity in various applications and has been the subject of numerous research studies. However, modelling and controlling a quadcopter to follow a trajectory is a challenging issue for which there is no unique solution. This study proposes an optimal hybrid quadcopter control with MPC-based backstepping control for following a reference trajectory. The outer-loop controller (backstepping controller) regulates the quadcopter’s position, whereas the inner-loop controller (Model Predictive Control) regulates its attitude. The translational and rotational dynamics of the quadcopter are analyzed utilizing the Newton-Euler method. After that, the backstepping controller (BC) is created, which is a recurrent control method according to Lyapunov’s theory that utilizes a genetic algorithm (GA) to choose the controller parameters automatically. In order to apply a linear control technique in the presence of nonlinearities in the quadcopter dynamics, Linear Parameter Varying (LPV) Model Predictive Control (MPC) structure is developed. Simulation validated the dynamic performance of the proposed optimal hybrid MPC-based backstepping controller of the quadcopter in following a given reference trajectory. The simulations demonstrate the fact that using a command control input in trajectory tracking, the proposed control algorithm offers suitable tracking over the assigned position references with maximum appropriate tracking errors of 0.1 m for the �� and �� positions and 0.15 m for the �� position.

Adaptive Control of Quadrotors in Uncertain Environments

The problem addressed in this article consists of the motion control of a quadrotor affected by model disturbances and uncertainties. In order to tackle model uncertainty, adaptive control based on reinforcement learning is used. The distinctive feature of this article, in comparison with other works on quadrotor control using reinforcement learning, is the exploration of the underlying optimal control problem in which a quadratic cost and a linear dynamics allow for an algorithm that runs in real time. Instead of identifying a plant model, adaptation is obtained by approximating the performance index given by the Q-function using directional forgetting recursive least squares that rely on a linear regressor built from quadratic functions of input/output data. The adaptive algorithm proposed is tested in simulation in a cascade control structure that drives a quadrotor. Simulations show the improvement in performance that results when the proposed algorithm is turned on.

Resilient coordination of multi-agent systems in the presence of unknown heterogeneous actuation efficiency and coupled dynamics: distributed approaches

To guarantee the stability and performance of an overall heterogeneous multi-agent system, feedback control structures must be capable of addressing the presence of heterogeneous agent-based nonlinear uncertainties, unknown actuation performance, and coupling effects. Additionally, some tasks require agents to track the leader's state and reach different states in a distributed way. Therefore, this paper proposes a distributed adaptive controller that drives a set of agents to user-assigned positions in the presence of the mentioned heterogeneous system anomalies. To address actuator dynamics, a hedging-based reference model is used to decouple adaptive updating from the actuator dynamics. To deal with the coupled dynamics, an observer-based estimation algorithm is proposed. Finally, the low-frequency learning method is used to deal with the high-frequency control response and, therefore, to obtain a better transient performance. The overall closed-loop system's stability is investigated using the Lyapunov Stability Theory, and the Linear Matrix Inequalities (LMI) technique is employed to identify stability limits regarding the actuator bandwidths of each agent. Illustrative numerical examples are presented to demonstrate the designed controller's performance in a heterogeneous uncertain multi-agent system's dynamics with unknown actuation capabilities and coupled dynamics.

Enhancing Internal Control Mechanisms in Local Government Organizations: A Crucial Step towards Mitigating Corruption and Ensuring Economic Development

Corruption poses a significant challenge to economic development and governance worldwide, with its detrimental effects permeating various levels of society. In the context of Greece, where corruption has been a longstanding issue, the role of internal audit mechanisms within local government organizations (LGOs) emerges as paramount. This paper presents a comprehensive analysis of the internal control landscape within LGO revenue departments, focusing on factors influencing its effectiveness and proposing strategies for improvement. Drawing upon survey data and regression analyses, this study highlights the crucial role of robust internal control mechanisms in combating corruption and fostering economic development. The findings underscore the importance of competent personnel, legislative compliance, interdepartmental collaboration, and technology utilization in enhancing internal control practices. Despite existing legislation, gaps in internal control implementation persist, including understaffing, inadequate procedures, and limited access to information. This study emphasizes the transformative potential of effective internal audit measures in mitigating corruption at the local level, thereby contributing to broader economic growth and societal well-being. Recommendations for strengthening the internal control structures within LGOs include the formal establishment of internal audit functions, adherence to professional standards, and the promotion of information system utilization. By addressing the corruption and inefficiencies within LGOs, this research underscores the pivotal role of institutional effectiveness in promoting transparency, accountability, and sustainable economic progress.

Unified centralized/decentralized voltage and frequency control structure for microgrids

This paper proposes a novel Unified Secondary Control Structure (USCS) for Microgrid (MG) systems. The proposed strategy ensures the benefits of centralized control and can maintain MG frequency and voltage regulation even during control or communication failures. In MG, one solution to ensure MG reliability in secondary control is to merge the advantages of both centralized and decentralized techniques. In order to ensure the operation of the proposed USCS, a novel decentralized secondary voltage control is proposed, where a local-based measure is employed; thus, communication is not required. The proposed controls are verified on an MG based on the CIGRE benchmark LV distribution network through hardware-in-the-loop simulation using the RTDS platform and an RTAC controller as the centralized control. The results show that the proposed control structure can guarantee regulation even during failures and restore it to regular operation afterward.

Kazakhstan's political repression in the first half of the 20th century: characteristics of the legislative mechanism governing the use of repressive measures

The research conducted enabled us to draw the conclusion that the mechanism of political repression during the studied period encompassed a range of legal and non- egal strategies, as well as organizational and social measures. These were implemented with the objective of attaining political objectives, safeguarding the exist-ing structure, ensuring state security, and upholding the unity of the totalitarian union state. The time under examination witnessed the establishment of both public and confidential departmental regulations, which ef-fectively safeguarded the legitimacy of political repression. These regulations comprehensively governed the whole process of implementing punitive actions. Simultaneously, the ruling bodies of the united communist party held exclusive authority in determining all significant decisions of state entities. The establishment of organizational and legal frameworks for political repression in the USSR was a fundamental component of the totalitarian control structure. This framework facilitated extensive human rights abuses and had a lasting impact on the historical trajectory of the Soviet population over an extended period. The examination of his-torical events of this nature enables us to comprehend the workings of totalitarian regimes and underscore the significance of the rule of law and autonomous institutions in safeguarding civil rights and liberties.

Solid-State Electrolytes by Electrospinning Techniques for Lithium Batteries.

Solid-state lithium batteries (SSLBs) are regarded as next-generation energy storage devices because of their advantages in terms of safety and energy density. However, the poor interfacial compatibility and low ionic conductivity seriously hinder their development. Electrospinning is considered as a promising method for fabricating solid-state electrolytes (SSEs) with controllable nanofiber structures, scalability, and cost-effectiveness. Numerous efforts are dedicated to electrospinning SSEs with high ionic conductivity and strong interfacial compatibility, but a comprehensive summary is lacking. Here, the history of electrospinning SSEs is overeviewed and introduce the electrospinning mechanism, followed by the manipulation of electrospun nanofibers and their utilization in SSEs, as well as various methods to improve the ionic conductivity of SSEs. Finally, new perspectives aimed at enhancing the performance of SSEs membranes and facilitating their industrialization are proposed. This review aims to provide a comprehensive overview and future perspective on electrospinning technology in SSEs, with the goal of guiding the further development of SSLBs.

Robust Gradient Hydrogel-Loaded Nanofiber Fleshy Artificial Skin Via A Coupled Microfluidic Electrospinning-Reactive Coating Strategy.

Skin regeneration attracts tremendous interest due to the important role of skin for human protection and beauty. Thus, methods allowing artificial skin to be carried out in a controllable fashion are potentially important for wound healing, which involves an intersection of materials, medicine, biology, and other disciplines. Herein, aiming at a new general methodology for fleshy materials, a new hydrogel-loaded hydrophobic-hydrophilic nanofiber fleshy artificial skin is designed and fabricated. The gradient hydrogel-loaded nanofiber artificial skin integrates both advantages of nanofiber and hydrogel, exhibiting fleshy feature (comparability to real skin in terms of appearance, texture, and function), excellent air permeability, compatibility, and good mechanical and antibacterial property. Interestingly, the efficient transport channels are formed throughout the hydrogel-loaded nanofiber structure, which is beneficial for water absorption and transfer. These advantages enable the establishment of a moist and favorable microenvironment; thus, greatly accelerating wound healing process. This work couples microfluidic electrospinning with reactive coating technique, which is in favor of material design and fabrication with controllable and uniform structures. The hydrogel-loaded nanofiber fleshy artificial skin shows comparability to real skin in terms of beauty, texture, and function, which would definitely provide new opportunities for the further optimization and upgrading of artificial skin.

Synchronous control of tri-motor vibration system considering an adaptive back-stepping control strategy

In oil and gas drilling engineering, the anti-phase synchronization of two co-rotating rotors in a tri-motor vibration system is easy to implement owing to its inherent coupling characteristics, which can lead to the exciting force generated by the vibrating system being very small. Thus, an adaptive back-stepping control strategy is proposed to apply in a tri-motor vibrating system and improve the processing capacity of drilling fluid shaker screens. The algorithm developed in this paper is that a complex higher-order nonlinear system is simplified into lower-order subsystems by the adaptive back-stepping control theory, and then the adaptive law for varying load torque is derived by combining with the adaptive theory to regulate the velocity of motors in a closed loop. Firstly, a dynamical model to describe the tri-motor vibration system is established, and the dynamical equations of the vibrating system are derived based on the Lagrange equation. Then, the speed error controller and the phase difference error controller are designed by combining the adaptive back-stepping control algorithm with the master–slave control (MSC) structure. According to Barbalat’s lemma, the stability of the control system is analyzed to verify the feasibility of the control method. Finally, the dynamical equations of the vibrating system are used to establish an electromechanical coupling control model of a tri-motor driven planar system through the Runge–Kutta method, and it verified the reliability of the control strategy, the robustness, and the stability of the control system, respectively, and intuitively revealed the synchronization characteristics of tri-motor vibration control system. The results demonstrate the phase difference among the three motors can be accurately stabilized at zero by a phase synchronization control strategy based on the adaptive back-stepping control method, and the method is simple and fast-speed and the control system has better robustness.

Modeling liquid rate through wellhead chokes using machine learning techniques

Precise measurement and prediction of the fluid flow rates in production wells are crucial for anticipating the production volume and hydrocarbon recovery and creating a steady and controllable flow regime in such wells. This study suggests two approaches to predict the flow rate through wellhead chokes. The first is a data-driven approach using different methods, namely: Adaptive boosting support vector regression (Adaboost-SVR), multivariate adaptive regression spline (MARS), radial basis function (RBF), and multilayer perceptron (MLP) with three algorithms: Levenberg–Marquardt (LM), bayesian-regularization (BR), and scaled conjugate gradient (SCG). The second is a developed correlation that depends on wellhead pressure (Pwh), gas-to-liquid ratio (GLR), and choke size (Dc). A dataset of 565 data points is available for model development. The performance of the two suggested approaches is compared with earlier correlations. Results revealed that the proposed models outperform the existing ones, with the Adaboost-SVR model showing the best performance with an average absolute percent relative error (AAPRE) of 5.15% and a correlation coefficient of 0.9784. Additionally, the results indicated that the developed correlation resulted in better predictions compared to the earlier ones. Furthermore, a sensitivity analysis of the input variable was also investigated in this study and revealed that the choke size variable had the most significant effect, while the Pwh and GLR showed a slight effect on the liquid rate. Eventually, the leverage approach showed that only 2.1% of the data points were in the suspicious range.