Main Control Parameters Research Articles

Liquid plugs in narrow tubes: application to airway occlusion

We study liquid plugs in the pulmonary airways based on the two-phase axisymmetric weighted residual integral boundary-layer model of Dietze et al. (J. Fluid Mech., vol. 894, 2020, A17), which was originally developed to study liquid films coating the inner surface of a cylindrical tube in interaction with a core gas flow. The augmented form of this model, which was never applied beyond a proof of concept, allows for the representation of liquid pseudo-plugs. Here, we demonstrate its predictive power vs experiments and direct numerical simulations, in terms of the dynamics of plug formation and the characteristics of developed liquid plugs, such as their shape, flow field, speed and length, as well as the associated wall stresses and their spatial derivatives. In particular, we show that the augmented model allows us to establish a direct continuation path from travelling-wave solutions (TWS) to travelling-plug solutions (TPS). We then apply the model to predict mucus plugs in the conducting zone of the tracheobronchial tree, based on the lung architecture model of Weibel. We proceed by numerical continuation of travelling-state solutions in terms of the airway generation, whereby we impose the wavelength of the linearly most-amplified convective instability (CI) mode or that of the absolute instability (AI) mode. We identify the critical airway generation for liquid-plug formation (TWS/TPS transition), maximum potential for wall-stress-induced epithelial cell damage and CI/AI transition, and investigate how these phenomena are affected by the main control parameters, i.e. airway orientation vs gravity, air flow rate, mucus properties and airway size.

Optimization of Magnetic Biochar Preparation Process, Based on Methylene Blue Adsorption.

The search for low-cost and effective adsorbents for the removal of organic dyes from contaminated water is urgently needed. The substantial amount of waste mushroom cultivation substrates generated in practical production can serve as an ideal material for the preparation of adsorbents. In this study, we investigated the main control parameters affecting the performance of magnetic mushroom substrate biochar and optimized the process of preparing biochar by using the Plackett-Burman and central composite design methods. Various analytical techniques including SEM, EDX, BET, and VSM were used to characterize the biochar. The results indicate that the carbonization temperature had the most significant impact on the yield and adsorption performance of biochar. Under the conditions of a carbonization temperature of 600 °C, a carbonization retention time of 1 h, and an impregnation ratio of 0.1, the yield and methylene blue adsorption value of magnetic biochar were 42.54% and 2297.04 μg/g, respectively, with a specific surface area of 37.17 m2/g. This biochar effectively removed methylene blue from the solution, demonstrating a high economic efficiency for wastewater treatment and pollution control. Furthermore, the adsorption-desorption cycle studies revealed its excellent stability and reusability. Additionally, based on the response surface methodology, a three-dimensional surface model of the adsorption performance of magnetic biochar under different carbonization conditions was established, providing a theoretical basis for the preparation of magnetic biochar from agricultural wastes.

Collective oscillations in a three-dimensional spin model with non-reciprocal interactions

Abstract We study the onset of collective oscillations at low temperature in a three-dimensional spin model with non-reciprocal short-range interactions. Performing numerical simulations of the model, the presence of a continuous phase transition to global oscillations is confirmed by a finite-size scaling analysis, yielding values of the exponents β and ν compatible with both the three-dimensional XY and Ising equilibrium universality classes. By systematically varying the interaction range, we show that collective oscillations in this spin model actually result from two successive phase transitions: a mean-field phase transition over finite-size neighborhoods, which leads to the emergence of local noisy oscillators, and a synchronization transition of local noisy oscillators, which generates coherent macroscopic oscillations. Using a Fokker–Planck equation under a local mean-field approximation, we derive from the spin dynamics coupled Langevin equations for the complex amplitudes describing noisy oscillations on a mesoscopic scale. The phase diagram of these coupled equations is qualitatively obtained from a fully-connected (mean-field) approximation. This analytical approach allows us to clearly disentangle the onset of local and global oscillations, and to identify the two main control parameters, expressed as combinations of the microscopic parameters of the spin dynamics, that control the phase diagram of the model.

Active roof-contacted combined backfill mining technology based on a modified magnesium slag-based cementitious material

Backfill mining technology is an inevitable choice for sustainable green mining. Full roof-contact of backfill is a key issue to ensure the long-term stability of the backfill mining technology, but no effective measures have been proposed. Based on the expansion characteristics of the modified magnesium slag-based filling material (MCM) and the shrinkage characteristics of the ordinary cement-bonded filling material (CFM), an active roof-contacted combined backfill mining technology (MCM-CFM) was proposed. The expansion characteristics and the uniaxial compressive strength (UCS) of the modified magnesium slag-based cementitious material (MC) were compared and analyzed. And the analytical expressions of the main control parameters as the axial force and the filling height of the backfill were derived, with or without lateral restraints. Then the sensitivity and the influence rule of the parameters were also investigated. The results show that: (1) the expansion rate of MC can reach 0.21% and increases rapidly in the early stage. At 28d and 40d, 84% and 95% of the total expansion deformation are reached, respectively, and the maximum expansion rate is 0.21%. (2) With or without lateral restraints, the height ratio of the upper and the lower filling parts is about 0.72 or 0.18, respectively. (3) The force subjected on the backfill is mainly controled by the parameters of the filling width, the elastic modulus and the expansion rate. (4) With or without lateral restraints, the height ratio of the two filling materials is controlled by the elastic modulus, the density or the elastic modulus, the Poisson’s ratio, the expansion rate, respectively. MCM-CFM can solve the problem of active roof-contact for backfill mining technology, and has the potential for large-scale application in mine backfilling.

DS based 2-DOF PID controller for various integrating processes with time delay

This study proposes a direct synthesis-based two-degree-of-freedom (2-DOF) controller for various types of integrating processes with time delays. This 2-DOF controller includes a proportional-integral-derivative (PID) controller to enhance load disturbance rejection performance and a set-point filter to improve servo response performance. The main PID controller parameters are expressed as process model parameters and a single adjustment variable, while the set-point filter is composed of PID controller parameters with weighted factors. The adjustment variable is tuned to achieve an optimal balance between response performance and robustness, based on the maximum magnitude of the sensitivity function (Ms). Controller parameters for various Ms values and guidelines for setting these parameters are provided in a consistent formulaic form using a curve-fitting method. These parameter-setting formulas facilitate the accurate implementation of PID controllers with specified Ms values and allow the controller design to be extended to processes with larger dimensionless time delays for a given Ms value. Although a 2-DOF controller was proposed, the adjustment variable for setting the parameters of the main PID controller and the set-point filter was solely the desired time constant. The proposed method was applied to various integrating processes with time delays, and its performance was compared with existing methods reported in the literature, based on performance indices such as settling time, overshoot, integral of absolute error, total variation in input usage, and global performance index. Simulations were conducted using six examples of various integrating processes with time delays to verify the effectiveness and applicability of the proposed controller.

Coupled calibration-control method for complex systems

We formulate the calibration-control dilemma which occurs in most interesting out-of-equilibrium dynamical systems in the natural and social sciences. Despite a lack of knowledge of the main control parameters, standard control methodology assumes that calibration can determine them. They are, however, obfuscated by the existence of control, leading to large undesired intermittent bursts, crises, and instabilities. By merging parameter calibration and control in a data assimilation framework, our joint calibration-control method nearly matches the performance achieved with complete knowledge of the system parameters, as demonstrated by both analytical and numerical simulations. This paves the way toward more versatile control of complex systems. Published by the American Physical Society 2024

Operation optimization of cement clinker production line based on neural network and genetic algorithm

The operation control plays a great role in the running performance of an industrial process. To achieve a successful control, the key point is searching for the target value of the control parameters. The relationship between operation parameters and performance parameters is usually nonlinear and complex, so it is hard to control an industrial process excellently with workers' experience. Based on a large amount of actual operation data, a bridge between control parameters and performance parameters might be built by the neural network. Prediction model is established by using neural network, genetic algorithm was then used to refine these parameters, the optimal condition can be further achieved by combining the relation bridge and genetic algorithm (GA). Paying attention to a cement clinker production process, this article established an optimizing approach based on the neural network and genetic algorithm and one-year operation data (615 sets). The feeding mass rate of raw meal and coal at the precalciner and the feeding coal mass rate at the rotary kiln are selected as the main independent variable and control parameters, and the specific standard coal consumption is determined as the key performance parameter and the optimization objective function. The mean square error and the correlation coefficient of the established neural network model are 12.84 and 0.89, respectively. The relative errors of approximately all prediction data (92.52 %) are within ±5 %. The optimal values for the raw meal feeding rate, the coal feeding rate into precalciner, and the coal feeding rate into rotary kiln are 259.57 t/h, 7.84 t/h, and 7.40 t/h, respectively. In that optimal condition, the specific standard coal consumption reaches 80.00 kgstandard coal/tclinker (This is a relative value, as there is a slight drift in zero point of the factory's instruments). A highly accurate neural network model is developed, which can significantly reduce standard coal consumption and improve industrial energy efficiency.

Modeling phase separation and composition patterning in FeCrAl alloys at neutron irradiation

Possible scenarios of the microstructural evolution of FeCrAl alloys under neutron irradiation are studied by using the phase-field method. The exploited approach is generalized by considering ballistic mixing of atoms, spatial rearrangement of point defects, and dynamics of their sinks (dislocation loops), self-consistently. Stability diagrams manifesting domains of main control parameters (irradiation temperature, damage rate, atomic relocation distance) governing precipitation are obtained. It is shown that depending on irradiation conditions a precipitation of the Cr-rich α′ -phase proceeds by either phase decomposition or composition patterning mechanism. Statistical analysis of precipitation kinetics is provided by studying precipitate number density, mean precipitate size and Chromium content in α′ -phase for a model alloy Fe-30%Cr-5%Al. A locality of point defects distribution with high concentration and dislocation loops growth are discussed. The hardening change is estimated for two possible scenarios of precipitation. Obtained results are verified with experimental observations. This study provides a deep insight into details of microstructural transformation in FeCrAl alloys during neutron irradiation.

An Adaptive Virtual Inertial Control Strategy for DC Distribution Networks

The DC distribution network is a low-inertia system, which is very sensitive to load disturbance, system failure, and other factors. By adding virtual capacitance to the converter connected to the power supply, the virtual inertia of the DC power grid can be improved. Firstly, this paper proposes a strategy for adjusting virtual capacitance based on the voltage change rate to achieve adaptive control of virtual inertia, which enables the converter to quickly absorb or release energy during power fluctuations. Secondly, the adaptivity of the strategy is improved and the main control parameters in the proposed control method are qualitatively analyzed. Finally, the four-terminal photovoltaic storage DC distribution network system is constructed. Through Simulink, the adaptive virtual inertia control is incorporated on the battery side to simulate and validate the effectiveness of the strategy and the rationality of parameter analysis. The results show that this method can provide flexible and adjustable inertia support for DC grids and improve the voltage stability of DC grids.

Design and analysis of a highly uniform five-band terahertz filter based on frequency selective surface

In this paper, a highly uniform five-band terahertz filter is presented, achieved by deforming two nested square ring structures. The metal pattern layer of the filter comprises a nested square ring structure with an inner and outer opening, and a metal strip connecting the inner and outer rings. Symmetrical openings divide nested square rings, breaking the current path and generating multiple metal bars of different lengths to excite dipole oscillations. Using metal strips to connect the inner and outer rings, the inner and outer resonant structures are integrated. Compared to a single resonant particle, the coupling of different single resonant particles amplifies the resonance of the combined structure, resulting in a wider stopband width and enhanced isolation between multiple passbands. A metal strip is also added to both ends of the outer ring opening to increase the equivalent capacitance of the outer ring, enhance the resonance, and improve out-of-band suppression. The transmission spectrum has five uniform passbands in the range of 1.3807–1.9917 THz, and the maximum passband ratio (MPR) of 3 dB bandwidth is about 1.16, and the ratio of 10 dB is about 1.17. The transmission coefficient of transmission zero is about 0.1, and the peak transmission coefficient of transmission peak is close to 1. The polarization of TE and TM incident waves is stable, and the filtering characteristics are good. Besides, the rectangular coefficients of the five passbands are all less than 1.33, showing excellent band selectivity. The resonance mechanism is explained by the Q value and electric field current distribution. The influence of structural parameter changes on filtering characteristics is also analyzed, and the main control parameters are found by using correlation analysis tools. From the changes in the MPR curve, it is verified that the structure parameters of the designed filter are in good condition. The multi-passband filter designed in this paper has uniform filtering characteristics, which is helpful to the development of terahertz multi-channel communication.

A Lyapunov based posture controller for a differential drive mobile robot

Driving a vehicle to a desired position and orientation is one of the most important problems that should be solved in most navigation systems. This paper describes a new complete design and hardware implementation of a two-level controller that will enable a differential drive mobile robot to reach any desired posture starting from any initial position. The first or low-level controller consists of a set of two proportional–integral–derivative (PID) controllers, running on an embedded system on board of the robot. These controllers provide the required voltages to the motors to make the left and right wheels of the robot rotate with the angular speeds computed by the second or high-level controller, running on a stationary PC system. This second controller is based on the Lyapunov stability theorem to derive two control laws for the kinematic model, used to transform the linear and angular speeds of the unicycle model in terms of left and right rotational speeds, required by the motors. As will be shown later, this architecture provides a very flexible way not only to tune the main controller parameters but also to get access and record all the system states.

Toward the ultimate efficiency of methane to syngas conversion by partial oxidation: A moving bed reactor with parallel preheating of reactants

The conversion of methane to syngas by partial oxidation combined with steam reforming in a counterflow moving bed reactor is theoretically considered. The conversion proceeds in filtration combustion mode with the non-premixed flows of steam–methane and oxidant gas. The flow of solid granular heat carrier is divided in two subflows used to preheat, respectively, steam–methane flow and oxidant gas flow prior to the reaction. The calculations are performed under assumption of thermodynamic equilibrium established in the reaction products. For the main control parameters – the flow rates of oxidant gas, steam, and solid heat carrier, related to the flow rate of methane – the parametric domain has been determined that provides a highly efficient conversion in the absence of soot in the products. Efficient heat recuperation with the solid heat carrier makes attainable conversion with the oxygen-to-methane molar ratio as low as 0.43. The flow arrangement with separate preheating of the reactants prior to reaction promises a highly efficient method of converting hydrocarbons to syngas or hydrogen.

Current state and approaches to automation of central heating stations at industrial enterprises

The paper examines the problems of forming technical requirements for the automation of central heating points of fuel and energy complex enterprises. The main technological schemes that are subject to automation are considered, the basic requirements for the installation of technical automation equipment are shown, the basic requirements are identified based on modern concepts for constructing automated control systems, and the main adjustable and controlled parameters of the central heating station for the main application in State Unitary Enterprise “Fuel and Energy Complex” are clarified.

Emotional expressivity in singing. Assessing physiological and acoustic indicators of two opera singers' voice characteristics.

In an earlier study, we analyzed how audio signals obtained from three professional opera singers varied when they sang one octave wide eight-tone scales in ten different emotional colors. The results showed systematic variations in voice source and long-term-average spectrum (LTAS) parameters associated with major emotion "families". For two of the singers, subglottal pressure (PSub) also was recorded, thus allowing analysis of an additional main physiological voice control parameter, glottal resistance (defined as the ratio between PSub and glottal flow), and related to glottal adduction. In the present study, we analyze voice source and LTAS parameters derived from the audio signal and their correlation with Psub and glottal resistance. The measured parameters showed a systematic relationship with the four emotion families observed in our previous study. They also varied systematically with values of the ten emotions along the valence, power, and arousal dimensions; valence showed a significant correlation with the ratio between acoustic voice source energy and subglottal pressure, while Power varied significantly with sound level and two measures related to the spectral dominance of the lowest spectrum partial. the fundamental.

INFLUENCE OF THE PATTERN OF THE COMBINED GRINDING SET OF THE DISC MILL ON INDIVIDUAL PAPER-FORMING PROPERTIES OF FIBROUS SEMI-FINISHED PRODUCTS AND THE PHYSICAL AND MECHANICAL CHARACTERISTICS OF THE FINISHED PRODUCT

The improvement of the process of grinding fibrous semi-finished products in pulp and paper production is caused by a reduction in the raw material base, requirements for the quality of finished products, as well as the desire to reduce production energy costs. Changing the grinding parameters allows you to change the properties and characteristics of the resulting materials in a wide range. The main controlled parameters of the grinding process are the gap between the rotor and stator disks, the rotor speed, the concentration of the fibrous mass. One of the important parameters of the grinding process is also the design of the grinding set. The article considers the influence of various configurations of cavities of the combined grinding set of a disc mill on the properties of the fibrous mass and finished paper castings. Individual paper-forming properties were evaluated, including the increase in the degree of grinding of the fibrous mass and the length of the fiber, as well as the physical and mechanical characteristics of the finished castings, which include the breaking length of the paper, the number of double folds and the tear resistance index. The grinding was carried out on a semi-industrial disc mill using a combined grinding set. For comparison, wavy and conical grinding cavities with straight unidirectional knives were selected. It was revealed that the wave-shaped grinding cavity has higher quality indicators in comparison with the conical grinding cavity by the nature of the impact on the fibrous mass.

Application research of BP neural network PID in control system of heat exchange station

In the direction of better resolution of time lag, nonlinearity and uncertainty in the heating system, a BPNN-PID (BP neural network PID) controller is proposed in this paper. A complete heating auto-control system is designed with the experimental platform of a university heat exchange station in Zhangjiakou as the research background. The auto-control system takes Programmable Logic Controller (PLC) as the control core, uses BPNN algorithm to optimize the PID control parameters, and finally takes outlet temperature of 1# plate exchanger as the main control parameter to conduct experimental research on BPNN-PID control and single-loop feedback control respectively. The results show that compared with the single-loop feedback controller, the PID control based on BPNN algorithm has superior control quality, with shorter adjustment time, smaller overshoot, finer control accuracy and stability.

Modeling vegetation patterning on sloped terrains: The role of toxic compounds

Vegetation patterning processes taking place on sloped terrains are here investigated through a class of three-compartments 1D reaction–advection–diffusion models enclosing the effects associated with the presence of toxic compounds. Focus is given to the transition from a uniformly-vegetated area to the desert state which occurs through the formation of an intermediate state characterized by non-stationary vegetation stripes. To this aim, linear stability analysis is addressed to characterize the mechanism of wave instability, responsible for the emergence of oscillatory Turing patterns. In detail, the analysis provides the critical value of the main control parameter as well as the wavelength and the migration speed at the onset of instability. Moreover, multiple-scale weakly nonlinear stability analysis is performed to describe the time evolution of the pattern amplitude close to the bifurcation threshold. Theoretical investigations are complemented by numerical simulations carried out for an extension of the Klausmeier kinetics that explicitly takes into account the interaction between autotoxicity and vegetation biomass. Numerical results provide several insights on how the interplay among mean annual rainfall, plant mortality and plant’s sensitivity to toxicity gives rise to different ecological scenarios.

Small‐signal impedance modelling and stability analysis of doubly fed induction generator‐based wind turbines during asymmetrical weak grid condition

AbstractDoubly fed induction generator (DFIG)‐based wind turbines (WTs) that connected into weak power grid may lose their stability. However, the stability issue becomes more complex and has not been well addressed during the asymmetric grid scenario, especially when the negative sequence current response is required, according to the latest grid codes. To settle such an issue, a small‐signal impedance model of the DFIG‐based WT with negative‐sequence current control is established in this paper. Based on the proposed model, the interaction mechanism between the DFIG and the imbalanced grid is analysed. The influence of the main physical and control parameters on the system stability is then assessed in detail. It is found that improper design of the notch filters in the control loop may arouse insufficient decoupling between the positive and negative components, which can further deteriorate the system stability and robustness. To cope with the problem, the setting rule of the quality factor of the second‐order notch filter, considering its dynamic and static characteristics, is derived. Simulations and experiments are finally conducted to validate the correctness of the theoretical analysis.

Characterization of Hydrotreated Vegetable Oil (HVO) in a Euro 6 Diesel Engine as a Drop-In Fuel and With a Dedicated Calibration

Renewable fuels can play an important role in achieving future goals of energy sustainability and CO2 reduction. In particular, hydrotreated vegetable oil (HVO) represents one of the most promising alternatives to petroleum-derived diesel fuels. Several studies have shown that conventional diesel engines can run on 100% HVO without significant modifications to the hardware and control strategies. The current activity has experimentally evaluated the potential of HVO as a “drop-in” fuel, i.e., without changes to the original baseline calibration, comparing it to conventional diesel fuel on a 2.3-litre Euro 6 compression ignition engine.Tests revealed that HVO can significantly reduce engine-out soot (by more than 60%), HC and CO emissions (by about 40%), compared to diesel, while NOx levels and fuel conversion efficiency remain relatively unchanged under steady-state warmed-up conditions. The advantages of HVO proved to be further enhanced when the engine has not yet warmed up.Using statistical techniques of design of experiments (DoE) at three warmed-up steady-state operating points, the main engine control parameters were recalibrated to demonstrate that engine-out emissions can be further optimized with a dedicated calibration.

LES study on traveling wave wall control for the wake of flow around a 3D circular cylinder at high Reynolds number

Flow around a cylinder is an important research problem in fluid mechanics. However, studies on traveling wave wall (TWW) flow control for the wake generated by the flow around a 3D cylinder remain limited. This study performs large eddy simulation (LES) to investigate the wake characteristics of flow around a three-dimensional (3D) circular cylinder with the TWW. The influence of the main control parameters of TWW on the aerodynamic forces and wake of the 3D cylinder is analyzed. The wake characteristics of the 3D cylinder at Re = 4 × 104 are obtained, and the traveling wave propagating downstream is achieved on the rear surface of the 3D cylinder using dynamic mesh. The control effects of wave amplitude, number of waves, and wave velocity of the traveling wave on the aerodynamic forces of the cylinder are analyzed, and the optimal control parameter combination is determined. The results demonstrate that the TWW control method completely eliminates the spanwise 3D flow characteristics of the cylinder when the amplitude ratio, number of waves, and velocity ratio are 0.02, 4, and 1.5, respectively. Moreover, it effectively suppresses the flow separation on the cylinder surface, eliminates the wake vortex, and suppresses vortex-induced vibration (VIV).