Adaptive Delay Research Articles

Improved Data-Driven Model-Free Adaptive Damping Controller Design for Interconnected Power Systems With Stochastic Communication Delays

The original model-based wide-area damping control (WADC) is difficult to obtain good damping performance due to the complex structure of interconnected power systems. In this paper, an improved data-driven model-free adaptive control (ID-MFAC) algorithm is proposed to design WADC for interconnected power systems with stochastic communication delays. First, the multiple-input multiple-output power system can be decoupled as multiple single-input single-output subsystems by considering controller interactions and system disturbances. Second, a step-size vector is designed to adjust the pseudo-partial derivative and make the algorithm more flexible by considering both input and output data adequately. Furthermore, an adaptive delay compensator is designed to compensate stochastic communication delays. Last, simulations are conducted to verify that the ID-MFAC algorithm can efficiently suppress multiple inter-area oscillations modes under various stochastic communication delays.

Restoration and coral adaptation delay, but do not prevent, climate-driven reef framework erosion of an inshore site in the Florida Keys

For reef framework to persist, calcium carbonate production by corals and other calcifiers needs to outpace loss due to physical, chemical, and biological erosion. This balance is both delicate and dynamic and is currently threatened by the effects of ocean warming and acidification. Although the protection and recovery of ecosystem functions are at the center of most restoration and conservation programs, decision makers are limited by the lack of predictive tools to forecast habitat persistence under different emission scenarios. To address this, we developed a modelling approach, based on carbonate budgets, that ties species-specific responses to site-specific global change using the latest generation of climate models projections (CMIP6). We applied this model to Cheeca Rocks, an outlier in the Florida Keys in terms of high coral cover, and explored the outcomes of restoration targets scheduled in the coming 20 years at this site by the Mission: Iconic Reefs restoration initiative. Additionally, we examined the potential effects of coral thermal adaptation by increasing the bleaching threshold by 0.25, 0.5, 1 and 2˚C. Regardless of coral adaptative capacity or restoration, net carbonate production at Cheeca Rocks declines heavily once the threshold for the onset of annual severe bleaching is reached. The switch from net accretion to net erosion, however, is significantly delayed by mitigation and adaptation. The maintenance of framework accretion until 2100 and beyond is possible under a decreased emission scenario coupled with thermal adaptation above 0.5˚C. Although restoration initiatives increase reef accretion estimates, Cheeca Rocks will only be able to keep pace with future sea-level rise in a world where anthropogenic CO2 emissions are reduced. Present results, however, attest to the potential of restoration interventions combined with increases in coral thermal tolerance to delay the onset of mass bleaching mortalities, possibly in time for a low-carbon economy to be implemented and complementary mitigation measures to become effective.

Real-time fast learning hardware implementation

Machine learning algorithms are widely used in many intelligent applications and cloud services. Currently, the hottest topic in this field is Deep Learning represented often by neural network structures. Deep learning is fully known as deep neural network, and artificial neural network is a typical machine learning method and an important way of deep learning. With the massive growth of data, deep learning research has made significant achievements and is widely used in natural language processing (NLP), image recognition, and autonomous driving. However, there are still many breakthroughs needed in the training time and energy consumption of deep learning. Based on our previous research on fast learning architecture for neural network, in this paper, a solution to minimize the learning time of a fully connected neural network is analysed theoretically. Therefore, we propose a new parallel algorithm structure and a training method with over-tuned parameters. This strategy finally leads to an adaptation delay and the impact of this delay on the learning performance is analyzed using a simple benchmark case study. It is shown that a reduction of the adaptation step size could be proposed to compensate errors due to the delayed adaptation, then the gain in processing time for the learning phase is analysed as a function of the network parameters chosen in this study. Finally, to realize the real-time learning, this solution is implemented with a FPGA due to the parallelism architecture and flexibility, this integration shows a good performance and low power consumption.

Adaptive delay dependent sliding mode fault-tolerant controller design for nonlinear systems with unknown time-varying input and state delays

This paper presents a novel adaptive delay-dependent fault-tolerant sliding mode control (SMC) strategy for the class of nonlinear Lipschitz systems with time-varying unknown delays in system states and inputs. A modified integral sliding surface (ISS) based on which the SMC approach is developed using a linear matrix inequality. Lyapunov-Krasovskii stability theory is employed to guarantee asymptotic stability of the closed-loop system such that system states starting from any arbitrary initial conditions with time-varying delays reach the predefined sliding surface in a finite time. It is also proved that states stay on the surface for all subsequent time, and the effects of the actuator’s faults are simultaneously attenuated. Adaptive tuning laws are used to adjust controller parameters and estimate actuators’ faults. The controllers’ structures are more straightforward than the most existing recent fault-tolerant control methods. Simulation results of practical nonlinear inverted pendulum system verified the outstanding merits and capabilities of the proposed scheme in the presence of actuators’ faults and multiple delays in the system states and inputs.

Adaptation delay causes a burst of mutations in bacteria responding to oxidative stress

Understanding the interplay between phenotypic and genetic adaptation is a focus of evolutionary biology. In bacteria, the oxidative stress response prevents mutagenesis by reactive oxygen species (ROS). We hypothesise that the stress response dynamics can therefore affect the timing of the mutation supply that fuels genetic adaptation to oxidative stress. We uncover that sudden hydrogen peroxide stress causes a burst of mutations. By developing single‐molecule and single‐cell microscopy methods, we determine how these mutation dynamics arise from phenotypic adaptation mechanisms. H2O2 signalling by the transcription factor OxyR rapidly induces ROS‐scavenging enzymes. However, an adaptation delay leaves cells vulnerable to the mutagenic and toxic effects of hydroxyl radicals generated by the Fenton reaction. Resulting DNA damage is counteracted by a spike in DNA repair activities during the adaptation delay. Absence of a mutation burst in cells with prior stress exposure or constitutive OxyR activation shows that the timing of phenotypic adaptation directly controls stress‐induced mutagenesis. Similar observations for alkylation stress show that mutation bursts are a general phenomenon associated with adaptation delays.

Power Management Strategies Based on Propellers Speed Control in Waves for Mitigating Power Fluctuations of Ships

This article proposes two novel power management strategies (PMSs) to enhance the electrical power quality in twin-screw all-electric ships (AESs) during vessel-wave encountering. Soothing PMS (SPMS) focuses on mitigating power fluctuations of the propulsion system since it has significant impacts on the power system in extreme conditions. For this purpose, the PMS modifies propellers’ speed based on the in-and-out-of-water effect loss factor (LF) in wave collisions. This method does not require typical equipment, such as energy storage systems (ESSs), to moderate the variations. Hence, it decreases the ESS demand capacity and maintenance costs at the design and operation levels. An integrated ship model is introduced to determine this LF in waves thoroughly. Furthermore, due to the propeller dynamics in speed altering, an adaptive delay is embedded in SPMS to improve its efficiency, and an advanced SPMS (ASPMS) is developed. To determine this varying adaptive delay during an operation, a straightforward algorithm is proposed, which does not impose the PMS to compute complex differential equations. Simulations reveal that both PMSs soothe the propulsion system power fluctuations and remarkably reduce the power system frequency and voltage variations. Meanwhile, the ASPMS surpasses the SPMS in terms of improving the power quality.

The impact of cerebellar transcranial direct current stimulation (tDCS) on sensorimotor and inter-sensory temporal recalibration

The characteristic temporal relationship between actions and their sensory outcomes allows us to distinguish self- from externally generated sensory events. However, the complex sensory environment can cause transient delays between action and outcome calling for flexible recalibration of predicted sensorimotor timing. Since the neural underpinnings of this process are largely unknown this study investigated the involvement of the cerebellum by means of cerebellar transcranial direct current stimulation (ctDCS). While receiving anodal, cathodal, dual-hemisphere or sham ctDCS, in an adaptation phase, participants were exposed to constant delays of 150 ms between actively or passively generated button presses and visual sensory outcomes. Recalibration in the same (visual outcome) and in another sensory modality (auditory outcome) was assessed in a subsequent test phase during which variable delays between button press and visual or auditory outcome had to be detected. Results indicated that temporal recalibration occurred in audition after anodal ctDCS while it was absent in vision. As the adaptation modality was visual, effects in audition suggest that recalibration occurred on a supra-modal level. In active conditions, anodal ctDCS improved sensorimotor recalibration at the delay level closest to the adaptation delay, suggesting a precise cerebellar-dependent temporal recalibration mechanism. In passive conditions, the facilitation of inter-sensory recalibration by anodal ctDCS was overall stronger and tuned to larger delays. These findings point to a role of the cerebellum in supra-modal temporal recalibration across sensorimotor and perceptual domains, but the differential manifestation of the effect across delay levels in active and passive conditions points to differences in the underlying mechanisms depending on the availability of action-based predictions. Furthermore, these results suggest that anodal ctDCS can be a promising tool for facilitating effects of temporal recalibration in sensorimotor and inter-sensory contexts.

A Wide-Input-Range Low-Profile Adaptive Delay Compensated Hysteretic LED Driver With Enhanced Current Accuracy

This article presents a wide-input-range low-profile dc–dc-based LED driver. An adaptive delay compensated hysteretic control (ADCHC) is proposed to adaptively modulate both peak and valley inductor currents for minimizing their current deviations, thereby enhancing the accuracy of the average LED current under different input and output voltages. A high-voltage current sensor with passive ripple filtering scheme is also developed to ensure fast and accurate inductor current sensing in the megahertz (MHz) range. The proposed LED driver was realized using two 100-V e-mode GaN FETs as power switches together with on-chip gate drivers and controller implemented in a 0.5- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> , 120-V process. This driver supports an input voltage range from 5 to 100 V and delivers a maximum output power of 25 W. The LED current error is minimized to within ±3.2% of the nominal 350-mA LED current under different input voltages and numbers of output LEDs. Compared with the prior art, the proposed LED driver has the smallest LED current error, operates 2 times higher frequency, and uses <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5\times $ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5.5\times $ </tex-math></inline-formula> smaller inductance and inductor volume. The proposed LED driver also features competitive peak power efficiency of 91.7% at 1.8-MHz frequency and 90-V input.

Modified CCF Based Shunt Active Power Filter Operation With Dead-Band Elimination for Effective Harmonic and Unbalance Compensation in 3-Phase 3-Wire System

The effect of reduction in the terminal voltage of a grid-tied inverter together with minimization in total harmonic distortion (THD) of terminal voltage and current, in the presence of dead-band in the switching remains always challenging for the researchers. With high switching frequency, this issue increases by many folds. The grid-tied inverter used for harmonic compensation acts as a shunt active power filter (SAPF). The implementation of the dead-band elimination technique is based on output current polarity detection, suffers from multiple zero-crossing due to the generation of high frequency switching harmonics during SAPF operation. This paper deals with a dead band elimination methodology together with harmonic compensation using SAPF under non-linear and unbalanced loading conditions. Here, SAPF uses a dual fundamental component extraction (DFCE) scheme with modified complex coefficient filter (MCCF) to extract fundamental components for reference current generation to implement an indirect current control PWM scheme. MCCF extracts fundamental components even in the presence of dc offset and unbalancing at the input. For incorporating dead-band elimination in control, exact polarity detection is done separately through SAPF output current estimation using sensed load current, and modified CCF computed reference source current. Since the estimated SAPF output current contains no high-frequency switching harmonics, the dead-band elimination technique can be correctly implemented. To synchronize the zero-crossing of the estimated and actual SAPF current, an adaptive delay control is used. The proposed MCCF based control logic’s performance together with the dead-band elimination technique is validated for SAPF operating under non-linear, unbalance, and dynamic load conditions. The proposed dead-band elimination scheme based SAPF model is developed and simulated using MATLAB/ SIMULINK. The simulation results show a significant reduction in source current harmonics due to the elimination of odd harmonic injection into the system by incorporating dead-band elimination in SAPF operation. The real-time simulation of the proposed method is also validated using OPAL-RT OP4510 real-time platform.

Adaptive Delay Compensator Based H_2/H_∞ Wide-Area Controller to Improve the Damping of Inter-Area Oscillations

Adaptive Delay Compensator Based H_2/H_∞ Wide-Area Controller to Improve the Damping of Inter-Area Oscillations

A Hybrid Scheme of MCS Selection and Spectrum Allocation for URLLC Traffic under Delay and Reliability Constraints.

The Ultra-Reliable Low-Latency Communication (URLLC) is expected to be an important feature of 5G and beyond networks. Supporting URLLC in a resource-efficient manner demands optimal Modulation and Coding Scheme (MCS) selection and spectrum allocation. This paper presents a study on MCS selection and spectrum allocation to support URLLC. The essential idea is to establish an analytical connection between the delay and reliability requirements of URLLC data transmission and the underlying MCS selection and spectrum allocation. In particular, the connection factors in fundamental aspects of wireless data communication include channel quality, coding and modulation, spectrum allocation and data traffic characteristics. With this connection, MCS selection and spectrum allocation can be efficiently performed based on the delay and reliability requirements of URLLC. Theoretical results in the scenario of a 5G New Radio system are presented, where the Signal-to-Noise Ratio (SNR) thresholds for adaptive MCS selection, data-transmission rate and delay, as well as spectrum allocation under different configurations, including data duplication, are discussed. Simulation results are also obtained and compared with the theoretical results, which validate the analysis and its efficiency.

High-Performance VLSI Architecture of DLMS Adaptive Filter for Fast-Convergence and Low-MSE

This brief presents a high-performance VLSI architecture of delayed least mean square (DLMS) adaptive filter for fast-convergence and low-mean square error (MSE) using distributed arithmetic (DA). The proposed design estimates response against the adaptation delays using a parallel predictive adder tree followed by a shift accumulate (SA) unit. An efficient quantization scheme with two bits of scaled error signal is also suggested. Single SA unit for multiple DA bases is used to reduce the number of adders and registers. Simulation and synthesis results show that the proposed design for 32 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">nd</sup> order provides 19.72% lesser area, 25.51% lesser power, lesser 28.89% MSE and 59.91% lesser MSE/area over the best existing design.

FPGA Delay-Oriented Process Mapping Algorithm of Xiangxi Minority Based on LUT

At present, FPGA (field-programmable gate array) architecture has made great progress in the requirements of hardware volume, which can meet common needs. However, for the increasing number of resources, it is difficult to significantly reduce the delay of process mapping. Therefore, this paper proposes FDMAP (fit descending map) algorithm from the perspective of the LUT number to reduce the delay. This paper proposes a method of FPGA mapping and debugging for heterogeneous multicore high-performance processors based on isomorphic symmetric FPGA architecture, which effectively utilizes the architectural features of heterogeneous multicore processors and the symmetric features of isomorphic FPGA, divides FPGA functions from top to bottom in a hierarchical way, and constructs FPGA architecture from bottom to top. Using differential bridge and adaptive delay adjustment sampling technology, combined with the embedded virtual logic analyzer debugging tool, FPGA architecture can be lightened and deployed quickly. Multicore complementary core-to-core replacement simulation mapping methods such as debug shells can be used to effectively complete the mapping of the target’s high-performance heterogeneous multicore processor to the entire SOC (system on-ship) chip system-level FPGA. In the aspect of algorithm, the fdmap algorithm is mainly implemented, and the low latency mapping of resources is realized with FPGA architecture. In order to verify the effectiveness of mapping the fdmap algorithm, this paper compares the fdmap algorithm with the vector VM algorithm. The research shows that when the wavelength resolution is 7 pm and the temperature error is less than 1°C, the shell is debugged, and 10 mapping examples are simulated with the fdmap algorithm. In the experiment, the LUT with the most critical 20% is selected, and the closed value of the LUT search type is set to 0.86. Compared with the original data, the number of LUTs increased by 15.2%, and the criticality decreased by 35.21%. Compared with the vector VM algorithm with the biggest gap, the number of LUTs decreased by 14.25%, the criticality improved by 14.21%, and the overall delay decreased by 65%. Therefore, the isomorphic symmetric FPGA architecture proposed in this paper can improve the structural criticality and significantly reduce the latency while reducing the number of LUTs.

Socially-Aware Adaptive Delay Tolerant Network (DTN) routing protocol.

Network partitioning and node disconnectivity results in high latency and frequent link disruption in DTNs. Therefore, routing a message toward a destined node is a challenge in such environment. Several DTN routing schemes have been introduced in this regard. Some, recently proposed DTN routing protocols either use a single or combination of multiple social metrics to identify the suitable forwarder node(s). However, these DTN routing protocols produced results at the expense of community formation cost and over utilization of network resources. To address these issues, we propose Socially-Aware Adaptive DTN (SAAD) routing scheme which exploits a social attribute known as Degree Centrality (DC). In this scheme, each node calculates and shares its DC with other nodes at regular intervals. A forwarder node disseminates message to the most influential node possessing highest DC. The proposed routing scheme works great in situations where someone want to improve the energy efficiency and want to involve only relevant nodes. The simulation results show that SAAD has improved to select the best node and has reduced the hop-count, overhead on the expense of delay as compared to Epidemic, PRoPHET and PRoPHETv2.

Metabolic adaptation delays time to reach weight loss goals.

The aim of this study was to determine whether metabolic adaptation, at the level of resting metabolic rate, was associated with time to reach weight loss goals, after adjusting for confounders. A total of 65 premenopausal women with overweight (BMI: 28.6 ± 1.5 kg/m2 ; age: 36.4 ± 5.9 years; 36 were White, and 29 were Black) followed an 800-kcal/d diet until BMI ≤25 kg/m2 . Body weight and composition were measured at baseline and after weight loss. Dietary adherence was calculated from total energy expenditure, determined by double labeled water, and body composition changes. Metabolic adaptation was defined as a significantly lower measured versus predicted resting metabolic rate (from own regression model). A regression model to predict time to reach weight loss goals was developed including target weight loss, energy deficit, dietary adherence, and metabolic adaptation as predictors. Participants lost on average 12.5 ± 3.1 kg (16.1% ± 3.4%) over 155.1 ± 49.2 days. Average dietary adherence was 63.6% ± 31.0%. There was significant metabolic adaptation after weight loss (-46 ± 113 kcal/d, p = 0.002) and this variable was a significant predictor of time to reach weight loss goals (β = -0.1, p = 0.041), even after adjusting for confounders (R2 adjusted = 0.63, p < 0.001). In premenopausal women with overweight, metabolic adaptation after a 16% weight loss increases the length of time necessary to achieve weight loss goals.

C20D3-Vitamin A Prevents Retinal Pigment Epithelium Atrophic Changes in a Mouse Model.

PurposeThis study aimed to evaluate the contribution of vitamin A dimerization to retinal pigment epithelium (RPE) atrophic changes. Leading causes of irreversible blindness, including Stargardt disease and age-related macular degeneration (AMD), occur as a result of atrophic changes in RPE. The cause of the RPE atrophic changes is not apparent. During the vitamin A cycle, vitamin A dimerizes, leading to vitamin A cycle byproducts, such as vitamin A dimers, in the RPE.MethodsTo study the consequence of vitamin A dimerization to RPE atrophic changes, we used a rodent model with accelerated vitamin A dimerization, Abca4−/−/Rdh8−/− mice, and the vitamin A analog C20D3-vitamin A to selectively ameliorate the accelerated rate of vitamin A dimerization.ResultsWe show that ameliorating the rate of vitamin A dimerization with C20D3-vitamin A mitigates pathological changes observed in the prodromal phase of the most prevalent retinal degenerative diseases, including fundus autofluorescence changes, dark adaptation delays, and signature RPE atrophic changes.ConclusionsData demonstrate that the dimerization of vitamin A during the vitamin A cycle is sufficient alone to cause the prerequisite RPE atrophic changes thought to be responsible for the leading causes of irreversible blindness and that correcting the dimerization rate with C20D3-vitamin A may be sufficient to prevent the RPE atrophic changes.Translational RelevancePreventing the dimerization of vitamin A with the vitamin A analog C20D3-vitamin A may be sufficient to alter the clinical course of the most prevalent forms of blindness, including Stargardt disease and age-related macular degeneration (AMD).

A CMOS Active Rectifier with Efficiency-Improving and Digitally Adaptive Delay Compensation for Wireless Power Transfer Systems

A CMOS active rectifier with digitally adaptive delay compensation for power efficiency improvement is presented in this work. The power transistors are turned on and turned off in advance under the control of the regenerated compensation signals, which are generated by the proposed compensation control circuit; therefore, the reverse current is eliminated, and the efficiency is increased. Simulation results in a standard 0.18 μm CMOS process show that the turn-on and turn-off delay of the rectifier is effectively compensated. The power efficiency is up to 90.6% when the proposed rectifier works at the operation frequency of 13.56 MHz.

Infancy weight gain and neurodevelopmental outcomes among term-born infants at age one year: A large prospective cohort study in China

ABSTRACT To investigate the association between infancy weight gain and neurodevelopment among term-born infants. Singleton term-born infants (n = 5837) were included from the Born in Guangzhou Cohort Study. Absolute weight gain was obtained by calculating the weight difference from birth to exactly 12 months. The primary outcome was neurodevelopment at age one year, which included five developmental domains. Global developmental delay was defined as delays in ≥3 domains. Multivariable logistic regression was used to examine the associations between infancy weight gain and neurodevelopment. Compared with infants gaining 6001–7000 g (reference group), infants gaining ≤5000 g had higher odds of delay in adaptive, gross motor, fine motor, social, and global developmental delay, infants gaining 5001–6000 g had higher odds of gross motor delay and social delay. A sex-stratified analysis showed that compared with the reference group, gaining ≤5000 g was associated with higher odds of fine motor delay in male infants, while gaining >7000 g was associated with higher odds of fine motor delay in females. Inadequate infancy weight gain is associated with higher odds of poor neurodevelopment at age one year among term-born infants.

IMPAIRMENTS IN CONE PIGMENT REGENERATION AND ABSOLUTE THRESHOLD IN MACULAR TELANGIECTASIA TYPE 2.

To test the hypothesis that Müller cell dysfunction in macular telangiectasia type 2 (MacTel) results in delayed cone adaptation kinetics and to assess absolute cone and rod thresholds in this condition. Adaptation after an approximate 63.5% full-field cone photopigment bleach was assessed for Goldmann size V (1.7° diameter) 640 nm (red) and 480 nm (blue) targets presented at a retinal locus corresponding to 2° temporal to fixation. The cone time constant of adaptation and absolute cone and rod thresholds were calculated from exponential functions fitted to the resultant dark adaptation curves. Eighteen eyes with MacTel (from 11 patients) were compared with 19 control eyes (from 16 normal subjects). Cone adaptation kinetics were significantly impaired in MacTel, as was the absolute cone threshold. Final thresholds for blue targets were also significantly elevated in MacTel, consistent with impaired rod absolute threshold. Losses in sensitivity observed in MacTel were consistent with a so-called d1/2 mechanism (i.e., receptoral) site of sensitivity loss. In addition to previously documented impairments in rod dark adaptation, MacTel results in a significant elevation in cone thresholds because of pathology at the level of the photoreceptors. The delays in cone adaptation that we found in eyes with MacTel may reflect impairment of the Müller cell-mediated cone-specific visual cycle.

A method for suppressing disorderly scheduling in multipath transmission scenarios using time delay offset

Multipath transmission enables packets to be distributed over different paths for transmission, andthis method has made full use of individual link resources. However, most existing multipath transmissionschemes lack suitable scheduling mechanisms and suffer from high disorder and packet loss.To address the disorder problem, this paper designs a delay offset method combined with link rejectionor adaptive delay adjustment mechanism to suppress the packet disorder problem in multipathtransmission scenarios based on an in-depth study of the background related to multipath transmission.Finally, a multipath link topology is built on the P4 simulation platform to implement the abovemethod in code simulation, and the experimental results are compared and analyzed with other twoscheduling mechanisms. The experimental results show that this method maintains the disorder levelwithin 5% compared with the single-path transmission and the equivalent multipath method, but thetransmission bandwidth is increased by nearly two times.