Time-delay Method Research Articles

Social Media Insight: Predicting Self-Harm Trends

Poisoning or injuring oneself can cause death or injury without intent. This is self-harm. Self-harm harms the perpetrators and the nation's economy. Studies have linked increased urbanization in emerging nations to rising self-harm and new technology. National self-harm patterns may be important for policymakers and public health experts to predict. This would allow them to immediately fix issues or avoid disasters. Studies have forecasted population-level self-harm patterns in many nations using simple statistics. In certain nations, prior data may be scarce or insufficient to make reliable projections. This makes it tougher to FAST assess and anticipate national self-harm. This essay proposes FAST, a technique that uses mental indicators from social media to forecast national self-harm trends. These markers can represent community mental health and help forecast self-harm patterns. Language-agnostic algorithms are taught to first identify mental indicators in gathered social media communications. These signals form multivariate time series. The time-delay embedding method then places these events in time. Last, many machine learning regressors are tried for future prediction. Tweets with 12 mental indicators may predict self-harm-related fatalities and injuries, according to a Thailand research. The suggested method predicted self-harm deaths and injuries. Better than ARIMA baseline by 43.56% and 36.48%. We think our research is the first to predict national self-harm trends using social media data. The findings improve self-harm prediction and establish the framework for new social network-based apps that forecast socioeconomic aspects. We used the top machine learning algorithms, Decision Tree and Voting Regressor. We found less MAE mistakes with these techniques.

Method for improving sound projection performance based on linearly constrained minimum power algorithm

Sound projection is a technique that utilizes directional sound sources to project sound wave onto reflective surfaces, aiming to create auditory events in the direction of projected sound, which can be achieved via loudspeaker arrays beamforming. Being limited by the focusing capability of loudspeaker array, the direct sound that reaches the listener earlier than the projected sound can influence the localization perception of projected sound due to the precedence effect. Therefore, for sound projection, it is crucial to reduce the direct sound intensity relative to the projected sound. In this study, a beamforming method of weakening direct sound is proposed to improve the performance of sound projection. Based on the linearly constrained minimum power algorithm, where a beamforming null is set in the direction of direct sound, a beamformer for a 16-unit linear loudspeaker arrays is designed to reduce the level of direct sound. Then, the ratio of reflected sound to direct sound (R/D ratio) is used as a criterion to evaluate the performance of the proposed method by simulation. The results show that the proposed method has significantly higher R/D ratio compared to the traditional time delay method, which validates the effectiveness in reducing the level of direct sound.

Dynamic mater-slave control strategy for transient coordination of inverter based microgrids under asymmetric faults

The ever-expanding inverter-based microgrids (MGs) require the grid-forming distributed renewable energy resources (DERs) to enhance the system safety. However, the different types of grid-forming DERs are prone to have transient conflicts with each other under short circuit faults, leading to unexpected outage or even system collapse. The fast response and poor overcurrent capability of DERs make transient coordination a challenge. This paper proposes a dynamic master–slave architecture for transient coordination control in islanded MGs under asymmetric faults. A dynamic reconfigurable voltage reference unit (DVRU) is designed according to the real faults. In this manner, the other DERs could comply with this DVRU to achieve both system voltage support, inrush current restraining, and power oscillation suppression. It is action signals instead of phase signals need to be transferred by the communication bus with the proposed local fault current differential time delay method (FCDDM). Thus, the low-bandwidth and the enhanced robust communication could be met under transient state. Additionally, the feasibility of the proposed method to combined with relay protection is analyzed. Finally, case study results on islanded MGs consisting of various grid-forming and grid-following DERs demonstrate the effectiveness and robustness of the proposed method under short circuit faults as well as communication failures.

Prediction method of particle size qualification rate of high-pressure roller mill based on end-edge-cloud synergy

The pass rate of granules is an essential indicator during the high-pressure grinding process, as it accurately reflects the processing quality. Currently, the pass rate of granules is detected primarily based on manual experience judgments or offline inspections. Hence, this article presents a methodology for predicting the pass rate of granularity via an optimized support vector regression approach improved through genetic algorithms. Initially, a time-delay analysis method based on the particle swarm optimization algorithm is applied to mitigate the effects of time delays between the granularity pass rate and other data, thus aligning the dataset on a temporal scale. Subsequently, the feature data were selected using the maximum information coefficient analysis technique, which identified the most significant variables for inclusion in the training and testing sets of the predictive model. Predictions are then made using a support vector machine model that has been enhanced via genetic algorithm optimization. Furthermore, an online prediction model has been established, enabling real-time forecasting of the granularity pass rate and online model updates through root mean square propagation gradient descent optimization algorithm. This method leverages end-edge-cloud collaboration to provide a smart detection mechanism for the throughput rate of particles in high-pressure grinding mills. Experimental results demonstrate that, compared to traditional time-delay analysis, the improved time-delay analysis method proposed in this study is more effective and accurate. Simultaneously, the ɛ-GASVR granularity pass-rate prediction model proposed in this article achieved an R2 of 0.89.

Analysis of Epileptic Seizures Stages through Attractor Dynamics

By employing mathematical procedures specific to non-linear dynamics, we devised a method for analyzing all the stages of an epileptic crisis. It can be seen that a specific attractor (reconstructed in the states space by time delay method) can be associated with each stage of the brain dynamics: normal functioning and epileptic crisis (pre-crisis, epileptic seizure, post-crisis). Moreover, since for each attractor a Hurst coefficient can be determined, we can state that each stage of an epileptic seizure can be characterized either by calculating the specific Hurst coefficient, or by calculating its fractal dimension.

Macro-micro synchronization strategy based on fuzzy time-delay compensation for high-precision laser on-the-fly processing

Real-time control systems of macro-micro manipulators commonly confront time-delay challenges to achieve high precision and synchronization performance, because macro and micro subsystems always have significant difference mainly in mechanical inertia. In this paper, a self-designed PC-based real-time controller utilized in laser on-the-fly processing is introduced as a study case of macro-micro systems. A dynamic time-delay compensation method for this case is proposed based on efficient fuzzy-model prediction and special data compression/extension algorithm. This method takes account of the practical time-delay fluctuation and has capability of adjusting the compensator adaptively rather than fixing the compensator as a constant, compared with the conventional static compensation. Experimental results show that, after applying the dynamic compensation, the process error caused by time-delay is eliminated from 1.059 mm to 0.001 mm, while the quality of synchronization appears even better than the static compensation with the error of 0.014 mm. Besides, the proposed method is computationally optimized, and the extra load of real-time kernel merely fluctuates within 3 % of the total computation performance capacity.

Complex dynamics and chaos control of a quantum Stackelberg game with heterogeneous players

In this research article, we explore the complex dynamics of a quantum Stackelberg game and its chaos control involving players with heterogeneous expectations. We utilize the Iqbal & Toor scheme to quantize the classical Stackelberg game and observe that the first mover advantage is diminished in the quantum version of the game. By examining the game from an evolutionary perspective, where the leader firm employs bounded rational expectations and the follower firm adopts adaptive expectations, we discover that the quantum Stackelberg game exhibits complex behaviors, such as cyclic and chaotic states. The local stability of the quantum game depends on the initial state of the game. Additionally, the occurrence of chaos is delayed in the quantum game. To further investigate, we implement the time-delayed feedback method to control the chaos in the quantum game and demonstrate that the techniques used for controlling the classical game are still effective in the quantum game.

Bifurcation Analysis and Chaos Control of Carrier Phase-Shifted Cascaded H-Bridge Inverter

Cascaded H-bridge inverters, which belong to strongly nonlinear time-varying system with complex dynamics, have been widely used in high-voltage and high-power engineering fields. In this paper, a carrier phase-shifted sinusoidal pulse-width modulation cascaded H-bridge inverter is taken as an example with piecewise analysis to establish the discrete iterative mathematical model. Furthermore, the nonlinear dynamic behavior of this inverter system is investigated using folding diagrams, spectrum diagrams, bifurcation diagrams, Lyapunov exponents, etc. We find that this inverter can exhibit multiperiod bifurcation, tangential bifurcation and paroxysmal chaos within certain ranges of control coefficients and other circuit parameters, which will influence the system’s stability seriously. On the basis of this discovery, the sinusoidal time-delay feedback control method is proposed. The difference between the load current of the controlled object and its own delay is used to form a feedback term, which is then fed into the sine function and proportional link to obtain the control term. Moreover, the Jacobian matrix of this feedback inverter system is derived, and the constraints on the feedback control coefficient are obtained based on the Jury criterion. Simulation results have verified the effectiveness of such a sinusoidal time-delay feedback control method, which can improve the stability and anti-interference of the system. The research can be used to provide some reference and guidance for the circuit design, debugging and control of cascaded H-bridge inverters.

Cross-Medium Time-Delay active vibration isolation method based on Voltage-Force hysteresis model

Micro-vibration significantly impacts spacecraft precision equipment operations, which can be resolved by using a piezoelectric actuator. The voltage-displacement relationship is the primary focus of current research on the hysteresis nonlinearity of piezoelectric actuators. Nevertheless, when tracking and controlling the acceleration/force signals of micro-vibration, control method based on the voltage-displacement introduces needless errors. In this paper, a cross-medium active vibration isolation control method based on voltage-force hysteresis model that can be utilised to track micro-vibration acceleration signals with high accuracy is proposed. The method exploits the slow transmission speed of vibration waves in a rubber medium to design a hybrid actuator mechanism containing a slow buffer medium and a piezoelectric actuator, and adopts a sliding mode control method to achieve accurate force control. Experiments demonstrated that compared with the vibration isolation control method based on voltage-displacement hysteresis model, the vibration isolation accuracy of the proposed method can be improved by 23.4%

Research on Delamination Damage Quantification Detection of CFRP Bending Plate Based on Lamb Wave Mode Control.

The carbon-fiber-reinforced polymer (CFRP) bending structure is widely used in aviation. The emergence and spread of delamination damage will decrease the safety of in-service bending structures. Lamb waves can effectively identify delamination damage as a high-damage-sensitivity detection tool. For this present study, the signal difference coefficient (SDC) was introduced to quantify delamination damage and evaluate the sensitivity of A0-mode and S0-mode Lamb waves to delamination damage. The simulation results show that compared with the S0-mode Lamb wave, the A0-mode Lamb wave exhibits higher delamination damage sensitivity. The delamination damage can be quantified based on the strong correlation between the SDC and the delamination damage size. The control effect of the linear array PZT phase time-delay method on the Lamb wave mode was investigated by simulation. The phase time-delay method realizes the generation of a single-mode Lamb wave, which can separately excite the A0-mode and S0-mode Lamb wave to identify delamination damage of different sizes. The A0-mode Lamb wave was excited by the developed one-dimensional miniaturized linear comb transducer (LCT), which was used to conduct the detection experiment on the CFRP bending plate with delamination damage sizes of Φ6.0 mm, Φ10.0 mm, and Φ15.0 mm. The experimental results verify the correctness of the simulation. According to the Hermite interpolation results of the finite-element simulation data, the relationship between the delamination damage size and the SDC was fitted by the Gaussian function and Rational function, which can accurately quantify the delamination damage. The absolute error of the delamination damage quantification with Gaussian and Rational fitting expression does not exceed 0.8 mm and 0.7 mm, and the percentage error is not more than 8% and 7%. The detection and signal processing methods employed in the present research are easy to operate and implement, and accurate delamination damage quantification results have been obtained.

A Novel Communication Time-Delay Cooperative Control Method with Switching Event-Triggered Strategy

A novel communication time-delay classification-based method is designed for nonlinear multiagent systems with the finite-time prescribed performance function. The time-delay phenomenon for communication channels between agents is discussed. Then, an improved time-delay classification method is proposed to broaden the standard of classification mechanism by considering the degree of deviation and relative variation of neighbor agents, rather than classifying the delay time into large time-delay and small time-delay. Based on this, the unified Lyapunov-Krasovskii functional and the finite-time performance function are used to solve the large time-delay phenomenon and ensure that the error is within the preset boundary, respectively. Furthermore, a modified switching event-triggered strategy is put forward to reduce the transmission burden, which considers the impact of tracking error to adjust the threshold condition in real-time. Additionally, all signals of the closed-loop systems are bounded. Eventually, two simulation examples verify the validity of the control strategy.

Generalized time-delay reverse synchronization with error feedback coefficients

To enhance the application of discrete chaotic systems in secure communication, we introduce a novel generalized time-delay inverse synchronization method with error feedback coefficient. This paper outlines the derivation of an inverse master-slave time-delay generalized synchronization system using the Lyapunov theory with error feedback coefficient design, which is proposed for the first time. To verify the efficacy of the synchronization method, we constructed a new 4D discrete hyperchaotic system. The dynamic properties of the novel system, such as the phase diagram and Lyapunov exponents, are investigated. Empirical outcomes reveal that generalized discrete time-delay synchronization can be accomplished under certain conditions for the error feedback coefficient. The study utilizes the chaotic masking technique to encrypt and decrypt messages in the secure communication system. The experimental findings reveal that by integrating the synchronization approach with the time-delay context of secure communication, the applicable design of the synchronization procedure is adaptable and trustworthy, catering to the pertinent requirements of engineering, and has the capacity to attain instantaneous chaotic synchronization requisites.

Time-delay Feedback Control of Fractional Chaotic Rössler Oscillator

In this research, we explore the utilization of the time-delayed feedback method to stabilize unstable steady states and aperiodic orbits within the chaotic fractional-order Rössler Oscillator. Employing the time-delay feedback control algorithm, we identify specific parameter ranges enabling the successful stabilization of unstable equilibria, considering variations in both feedback gain and time delay. Unlike previous research works where Caputo and Riemann-Liouville characterization of fractional derivatives are used, we are using Grünwald-Letnikov (GL) characterization because of its simplicity and ease of implementation and demonstrating the stability using the analytical and numerical analysis and plots of eigenvalues. Additionally, our analysis highlight the effectiveness of a sinusoidally modulated time delay in the control law, significantly expanding the stability region of steady states beyond the capabilities of the traditional time-delayed feedback scheme with a constant delay. Furthermore, the analysis of eigenvalues before and after applying the control strategy offers tangible insights into the system's stability dynamics.

A Manufacturability‐Driven Method for Designing Metamaterial Focusing Acoustical Lenses

Herein, a method for designing and fabricating acoustic metamaterial focusing lenses for imaging applications such as nondestructive testing is proposed. First, a refractive index distribution is designed using the time delay method for a target focal length. Second, unit cell structures that can achieve the required refractive indices are found using the effective property retrieval method. At this point, factors such as fabrication cost and manufacturing limitations are considered. Finally, the pressure field from the designed lens is calculated using finite element (FE) modelling and iterated until the required focusing performance is achieved. To increase manufacturability, the unit cells necessarily become larger than required for the homogeneous regime. As an example, a lens of focal length 200 ± 10 mm at a frequency of 40 kHz is designed using cross‐shaped unit cells and fabricated using three‐dimensional printing. The design methodology leads to 2.4 mm (wavelength/3.6) unit cells which operate near the cut‐off frequency of the first mode. The lens is experimentally tested, achieving a focal length of 208 mm and a focal width of 12 mm (1.4 × wavelength), and showing good agreement with an FE model. The focusing ability of the lens is demonstrated by measuring the size of various holes in thin plates.

A Multiple-False-Target ISAR Shape Deception Jamming Method Based on Improved Template Multiplication Modulated Time-Delay Algorithm and Sub-Nyquist Sampling

In recent decades, the deception jamming approach based on digital radio frequency memory (DRFM) for inverse synthetic aperture radar (ISAR) has been a well-researched topic. Various types of jamming signals based on interrupted-sampling repeater jamming (ISRJ) can induce one-dimensional multiple high-resolution range profile (HRRP) false targets or two-dimensional realistic multiple ISAR false targets for deception. However, these existing methods generate false targets that are identical to the real target. The ISRJ false target also generates a main false target whose energy is much higher than other sub-false targets. Thus, it is easy to discover that the radar has suffered jamming. In order to generate better, more confusing jamming signals, this paper proposes a jamming method based on sub-Nyquist sampling jamming to induce realistic, multiple false targets on ISAR images. It improves a template multiplication modulated time-delay method to eliminate and add scatterers on the selected false target to change its ISAR shape. The frequency-shift parameters of the template jamming signal are analyzed and derived in detail for eliminating and adding scatterers at the specified location. Thus, multiple false targets with different ISAR shapes and similar energy are generated, which can create better deception effects. Meanwhile, this method can adjust the number of false targets and the location of changed-shape false targets. Furthermore, the resolution of the false target can adaptively change with the radar pulse width and the accumulated pulse number. The simulation results show that the proposed deception jamming strategy works.

Broadband ultrafast ultraviolet laser output by using β-BaB2O4 crystal

In this paper, a broadband ultrafast ultraviolet (UV) laser was generated through sum-frequency method with β-BaB2O4 (BBO) crystal by using a femtosecond (fs) Ti:sapphire laser as the fundamental laser source. We studied the influence of the power ratio between the fundamental frequency and second harmonic laser beams on output power and conversion efficiency of UV laser. The time delay method was used to change the optical path difference in the sum-frequency generation (SFG). At the same time, the cutting angle of the crystal was optimized and the effect of different focal lengths of lenses on the experimental results was studied. Finally, we obtained a tunable UV laser beam with a tuning range from 226.7 nm to 360 nm generated by the BBO crystal. The laser had high conversion efficiency, and the maximum output power was 540 mW at 270 nm.

Bifurcation control of solid angle car-following model through a time-delay feedback method

Bifurcation control of solid angle car-following model through a time-delay feedback method

Research on identification of the hydraulic and structural vibration sources in a tubular pumping station

The hydraulic and structural vibration sources of pumping station are investigated in current research. Based on a vertical shaft tubular pumping station project in an eastern province of China, a three-dimensional fluid-solid coupling model of the pumping station is established, including the fluid in the flow channel, concrete structure, and hydraulic machinery. Two-way fluid-structure interaction (FSI) method is used to calculate the coupled vibration responses of the pumping station. Based on the FSI simulation results, the hydraulic and structural vibration sources of the pumping station are explored from the frequency perspective based on the Fourier transform theory and the vibration energy transmission perspective based on the time-delayed transfer entropy method. Research results show that the fluid pulsation generated by the rotation of the impeller is the main hydraulic vibration source, and the rotating impeller is the main structural vibration source that causes the vibration of the unit and the concrete structure. This research could provide a scientific basis for structural vibration control, vibration reduction, and isolation design of the pumping station.

Double voltage vector model predictive control for grid-connected cascade H-bridge multilevel inverter with fixed switching frequency

Model predictive control (MPC) is an outstanding control method which can achieve superior dynamic response, nonlinear control and multi-objective collaborative control. However, because of unfixed switching frequency, the harmonic spectrum of the output current is dispersed, which would make it difficult to design the output filter. In this work, a double voltage vector model predictive control (DVV-MPC) algorithm for grid-connected cascade H-bridge (CHB) multilevel inverter is presented. The algorithm not only has the advantages of MPC but also produces fixed the switching frequency of the inverter. It is realized by a modulation stage with two adjacent voltage vectors in one switching cycle. And the duty cycle of the associated voltage level is obtained by minimizing an additional cost function. This method is suitable for the cascades of n cells inverter. For reducing the computation burden and eliminating the computation delay, adjacent regions prediction method and time-delay compensation method are applied to the inverter. Finally, in this paper, the proposed strategy is applied to a single-phase grid-connected 7-level CHB inverter. Simulation and experiment are executed to show the advantages of the proposed control algorithm in dynamic state and steady state.

Prediction and Control of Small Deviation in the Time-Delay of the Image Tracker in an Intelligent Electro-Optical Detection System

A small deviation in the time-delay of the image tracker is essential for improving the tracking precision of an electro-optical system, and for future advances in actuator technology. The core goal of this manuscript is to address issues such as tracking the controller time-delay compensation and the precision of an electro-optical detection system using an advanced filter design, a fire control modeling, and an anti-occlusion target detection system. To address this problem, a small deviation in the time-delay prediction and control method of the image tracker is proposed based on the principle of linear motion transformation. The time-delay error formation is analyzed in detail to reveal the scientific mechanism between the tracking controller feedback and the line-of-sight position correction. An advanced N-step Kalman filtering controller model is established by combining a line-of-sight firing control judgment and a single-sample training anti-occlusion DSST target tracking strategy. Finally, an actuator platform with three degrees of freedom is used to test the optical mechatronics system. The results show that the distribution probability of the line-of-sight measuring error in a circle with a radius of 0.15 mrad is 72%. Compared with the traditional control method, the tracking precision of the optimal method is improved by 58.3%.