Intermittent Strategy Research Articles

ICheck: Progressive Checkpointing for Intermittent Systems

Energy harvesting devices powered by ambient energies, instead of batteries, have been drawn lots of attention due to their advantages of energy saving, easy deployment without relying on stable power sources, and smaller sizes, facilitating promising applications, such as environmental and health monitoring. These devices perform the computations intermittently, where the code executions are halted and resumed depending on the availability of the harvested energy. On such devices, the capacitors are present and served as the energy buffers for preserving the program states when sudden power outages occur. Nevertheless, the capacitors have relatively shorter lifetimes, compared with the rest of hardware components on the devices, and larger capacitors, which are desired by the systems requiring complex computations, hamper the achievement of device miniaturization, e.g., for medical implants or smart dust. In this article, we propose a new intermittent checkpointing strategy, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">iCheck</i> , to tackle the issues raised for the program-state retaining when the capacitors are not functioning correctly (or when the capacitor-less devices are adopted). The proposed <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">iCheck</i> is designed to perform the checkpointing-based program-state preserving progressively with being aware of the power-failure characteristics of the harvested energy source to maximize the progress forwarding and to ensure data consistency while encountering incomplete checkpoints caused by sudden power losses. The proposed design is evaluated with a series of experiments with encouraging results.

Energy conversion performance of a PV/T-PCM system under different thermal regulation strategies

The photoelectric conversion efficiency generally decreases with increasing temperature of a photovoltaic (PV) panel; therefore, temperature control is the key issue in the photovoltaic/thermal (PV/T) system. We experimentally analyzed the energy conversion performance of a PV/T system combined with a latent heat solar collector under the real outdoor climate of Shanghai. The solar collector was filled with the phase change material (PCM) of fatty acid for cooling the PV panel. Five cases under different thermal regulation strategies for the PV/T-PCM system were comprehensively analyzed to optimize the system performance. The results indicated that the temperature stratification of PCM was still significant in the solar collector even when metal fins were employed. The temperature fluctuation of the PV panel can be well alleviated by PCM; however, the PCM was easily overheated under long-term operation of the PV/T-PCM system. Among the five cases, the overall energy efficiency of the PV/T-PCM system with full-time thermal regulation was 5.4% and 22.2% higher than the two systems without thermal regulation, respectively. The relatively low temperature setting of the thermal regulation strategy facilitated the heat transfer from the PCM. In comparison with the full-time thermal regulation strategy, the 45 °C intermittent thermal regulation strategy (Case 4) demonstrated the best performance. The total energy and exergy efficiencies of Case 4 were 86.3% and 15.5%. The exergy efficiency of thermal energy varied slightly in the range of 1.1%–1.4% for the five cases. It was concluded that the energy conversion performance of the PV/T-PCM system could be significantly improved by a suitable intermittent thermal regulation strategy.

Practical Recommendations for the Topical Treatment of Atopic Dermatitis in South and East Asia

IntroductionThere is some evidence to suggest that the prevalence of atopic dermatitis (AD) in Asia is rising. We have therefore developed an algorithm for the topical treatment of AD throughout South and East Asia for use by primary care physicians, pediatricians and dermatologists.MethodsNine AD experts from South and East Asia and one from Europe developed the algorithm based upon treatment guidelines, relevant literature and local treatment practices. The algorithm outlines current best practice for the use of emollients, topical corticosteroids (TCS) and topical calcineurin inhibitors (TCI), with the intention of simplifying the treatment regimen of mild-to-moderate AD in South and East Asia.ResultsPatients with AD should bathe and cleanse affected skin to remove crusts and scales daily. Emollients should also be applied daily as a maintenance treatment. When selecting appropriate topical anti-inflammatory treatment for AD flares, several factors should be taken into consideration, including the patient’s age, attitude to treatment options and site of AD lesions. Given the concerns regarding the risk of skin atrophy with use of TCS, a TCI should be used to treat AD lesions in sensitive skin areas: pimecrolimus is recommended for mild-to-moderate AD in these locations, while tacrolimus should be considered for moderate and severe cases. Either pimecrolimus or tacrolimus is recommended for flares in other, non-sensitive body locations. A proactive or intermittent maintenance treatment strategy involving regular emollient use and twice-weekly application of a TCI to previously affected areas is encouraged to reduce the risk of flares.ConclusionsThe algorithm proposed here is intended to simplify the topical treatment of mild-to-moderate AD in daily practice in South and East Asian countries.

Variance‐constrained H∞ synchronization control of discrete time‐delayed complex dynamical networks: An intermittent pinning approach

AbstractIn this paper, the variance‐constrained H∞ synchronization control problem is investigated for a class of discrete time‐delayed complex dynamical networks. Considering the case where a dynamical network cannot achieve the synchronization by itself, the feedback controllers are added to drive the network toward a desired orbit. To further decrease both the frequency of controller update and the energy consumption, an intermittent pinning strategy is developed to control only a small part of the network nodes. The purpose of the addressed synchronization control problem is to design a set of feedback controllers such that the closed‐loop system achieves both the prescribed H∞ disturbance attenuation level and the variance constraints. By resorting to a combination of the Lyapunov stability theory and the switching system approach, a sufficient condition is obtained under which the dynamical network reaches the overall synchronization. Furthermore, the expected gains of the intermittent pinning controllers are parameterized by solving a set of linear matrix inequalities. Finally, a numerical example is exploited to verify the effectiveness of our proposed theoretical results.

Intermittent control strategy can enhance stabilization robustness in bumblebee hovering

Active flight control plays a crucial role in stabilizing the body posture of insects to stay aloft under a complex natural environment. Insects can achieve a closed-loop flight control by integrating the external mechanical system and the internal working system through manipulating wing kinematics according to feedback information from multiple sensors. While studies of proportional derivative/proportional integral derivative-based algorithms are the main subject to explore the continuous flight control mechanisms associated with insect flights, it is normally observed that insects achieve an intermittent spike firing in steering muscles to manipulate wings in flight control discontinuously. Here we proposed a novel intermittent control strategy for a 3 degree of freedom (DoF) pitch-control and explored its stabilization robustness in bumblebee hovering. An integrated computational model was established and validated, which comprises an insect-inspired dynamic flight simulator and a novel discrete feedback controller as well as a simplified free-flight dynamic model. We found that the intermittent control model can achieve an angular-dominant flight control, whereas the continuous control model corresponds to an angular-velocity-dominant one. Given the biological constraints in sensorimotor neurobiology and musculoskeletal mechanics, the intermittent control strategy was examined capable of enhancing the stabilization robustness in terms of sensory latency, stroke derivation, spike interval, and damping strength. Our results indicate that the intermittent control strategy is likely a sophisticated flight control mechanism in insect flights while providing a bioinspired flight-control design for insect size flapping-wing micro air vehicles.

Pinning exponential boundedness of fractional-order multi-agent systems with intermittent combination event-triggered protocol

ABSTRACT This paper mainly deals with the exponential boundedness of fractional-order multi-agent systems (FOMSs). A novel controller, intermittent combination event-triggered strategy, is proposed to save more control resources. Unlike the traditional event-triggered mechanism, the combined event-triggered strategy includes the item of the error function and exponential function. The communication between agents is intermittent. Under the pinning control, only a few agents can receive information from the virtual leader. By utilising the designed controller, sufficient conditions for exponential boundedness of FOMSs are gained along with fractional-order Lyapunov methods, the monotonicity of the Mittag-Leffler function and matrix analysis. The article also investigates the consensus of FOMSs via pinning combination event-triggered control without the intermittent mechanism through the same analytical approach. The Zeno behaviour is also excluded. Simulations are given to verify the availability and applicability of the designed protocol. Experiments demonstrate that the combined event-triggered mechanism can reduce the number of event triggers.

Leader-Following Mean Square Consensus of Stochastic Multi-agent Systems via Periodically Intermittent Event-Triggered Control

This paper investigates the leader-following mean square consensus of stochastic multi-agent systems. Firstly, an intermittent event-triggered strategy along with triggering conditions has been presented. Next, a novel Lemma has been established to overcome the difficulty which stems from integrating intermittent strategy into event-triggered strategy. With aid of the established Lemma and some stochastic analysis techniques, two sufficient criteria on consensus of stochastic multi-agent systems via the proposed strategy have been derived. Finally, three numerical examples are presented to demonstrate the effectiveness of theoretical results.

Evaluating the Effects of Different Sleep Supplement Modes in Attenuating Metabolic Consequences of Night Shift Work Using Rat Model.

PurposeTo study the effects of chronic-simulated night shift work using the rat model and examines if a particular sleep supplement mode could be better in alleviating the effects.MethodsThe male Wistar rats were randomly divided into the control (CTL: 8 rats) and night shift work (NW: 24 rats) groups of rats. Based on the sleep supplement strategy, the NW group was further segregated into three subgroups (8 rats each); late sleep supplement group (LSS), early sleep supplement group (ESS), and intermittent sleep supplement group (ISS). Sleep deprivation was achieved using the standard small-platform-over water method. Parameters such as animal body weight and food intake were measured daily. The intraperitoneal glucose tolerance test, fasting plasma insulin concentration, insulin resistance index and insulin sensitivity were measured twice, in the 4th and 8th weeks of the study. Plasma corticosterone concentration and pathological changes in islets (insulitis) were measured at the end of the 8th week.ResultsIn NW group, night work resulted in a gain of body weight and albeit lower than that of the CTL group. NW rats also had higher food intake, showed impaired glucose metabolism and higher plasma corticosterone concentration. The sleep supplement experiments suggested that compared to the other modes, intermittent sleep supplement had significantly low changes in the body weight, glucose metabolism and the islet cells.ConclusionSimilar to previous studies, we also found that night shift work adversely impacts the body weight and glucose metabolism in rats. However, upon evaluating different sleep supplement strategies, we found the intermittent sleep supplement strategy to be most effective.

The impact of mechanical ventilation operation strategies on indoor CO2 concentration and air exchange rates in residential buildings

In Portugal, residential buildings commonly have their ventilation strategy changed after commissioning. This occurs due to the building managers' willingness to reduce shared costs with the electricity needed for fan operation. However, this option is not technically supported, and the effects of such a strategy on indoor air quality-related to human pollutants are yet to be quantified. CO2 was monitored in 15 bedrooms and air exchange rates were calculated for each room. The air exchange rate values ranged from 0.18 to 0.53 h−1 when mechanical extraction ventilation was off, and from 0.45 to 0.90 h−1 when mechanical extraction ventilation was on, which represents an average increase of 119%. With the current intermittent ventilation strategy, all rooms remain above 1500 ppm for a given percentage of time, and 12 rooms presenting CO2 concentrations above 2000 ppm. Simulations of theoretical CO2 concentrations, for a non-interrupted mechanical ventilation strategy show that no rooms would accumulate CO2 concentrations above 2000 ppm, and only 25% would present CO2 concentrations above 1500 ppm. Pearson correlations between the monitored CO2 and human and spatial factors identified two relevant parameters. Those parameters correspond to ratios between CO2 generation and floor area ([Formula: see text]), and airflow with CO2 generation ([Formula: see text]). The proposed ratios could be used as ways to optimise ventilation costs and indoor air quality.

A Mathematical Model of Intermittent Gas Lift in Elevation-Production Operation with Line-Pack and Line-Drafting Phenomena in a Gas Line

This paper discusses a transient model of the intermittent gas lift technique in an oil well. The model is developed in the gas line, in the tubing-casing annulus, and the tubing. The line-pack and line-drafting phenomena in the gas line are considered in the model. A numerical approach will be used to solve the mathematical model that represents fluid flow during intermittent gas lift injection. The dynamics of important variables in the intermittent gas lift are investigated and analyzed to determine the best production strategy for intermittent gas lift. The variables are film thickness and velocity, slug height and velocity, and gas height and velocity. The relationships between surface injection control parameters (gas injection pressure and gas injection rate) and the velocity and height of film, gas, and liquid are shown in one cycle of the gas lift intermittent process. The higher the gas injection pressure, the faster the gas injection velocity, and the thinner the film thickness in the tubing. In order to obtain clean tubing from film thickness, the gas injection pressure needs to be optimized, which will lead to maintaining compressor discharge pressure availability. Detailed observation of the dynamic performance inside the tubing production well will give the optimum oil production rate for oil wells under a gas lift intermittent production strategy for field application.

A network model of Italy shows that intermittent regional strategies can alleviate the COVID-19 epidemic

The COVID-19 epidemic hit Italy particularly hard, yielding the implementation of strict national lockdown rules. Previous modelling studies at the national level overlooked the fact that Italy is divided into administrative regions which can independently oversee their own share of the Italian National Health Service. Here, we show that heterogeneity between regions is essential to understand the spread of the epidemic and to design effective strategies to control the disease. We model Italy as a network of regions and parameterize the model of each region on real data spanning over two months from the initial outbreak. We confirm the effectiveness at the regional level of the national lockdown strategy and propose coordinated regional interventions to prevent future national lockdowns, while avoiding saturation of the regional health systems and mitigating impact on costs. Our study and methodology can be easily extended to other levels of granularity to support policy- and decision-makers.

Screening for atrial fibrillation: predicted sensitivity of short, intermittent electrocardiogram recordings in an asymptomatic at-risk population.

AimsScreening for asymptomatic atrial fibrillation (AF) could prevent strokes and save lives, but the AF burden of those detected can impact prognosis. New technologies enable continuous monitoring or intermittent electrocardiogram (ECG) snapshots, however, the relationship between AF detection rates and the burden of AF found with intermittent strategies is unknown. We simulated the likelihood of detecting AF using real-world 2-week continuous ECG recordings and developed a generalizable model for AF detection strategies.Methods and resultsFrom 1738 asymptomatic screened individuals, ECG data of 69 individuals (mean age 76.3, median burden 1.9%) with new AF found during 14 days continuous monitoring were used to simulate 30 seconds ECG snapshots one to four times daily for 14 days. Based on this simulation, 35–66% of individuals with AF would be detected using intermittent screening. Twice-daily snapshots for 2 weeks missed 48% of those detected by continuous monitoring, but mean burden was 0.68% vs. 4% in those detected (P < 0.001). In a cohort of 6235 patients (mean age 69.2, median burden 4.6%) with paroxysmal AF during clinically indicated monitoring, simulated detection rates were 53–76%. The Markovian model of AF detection using mean episode duration and mean burden simulated actual AF detection with ≤9% error across the range of screening frequencies and durations.ConclusionUsing twice-daily ECG snapshots over 2 weeks would detect only half of individuals discovered to have AF by continuous recordings, but AF burden of those missed was low. A model predicting AF detection, validated using real-world data, could assist development of optimized AF screening programmes.

Home-Based Transcranial Direct Current Stimulation (tDCS) to Prevent and Treat Symptoms Related to Stress: A Potential Tool to Remediate the Behavioral Consequences of the COVID-19 Isolation Measures?

The WHO has recommended self-isolation and social distancing measures for containing the coronavirus 19 (COVID-19) pandemic, and the Centers of Disease Control and Prevention (CDC) and the vast majority of countries have adopted it, with strategies varying in terms of degrees of containment (Wilder-Smith and Freedman, 2020). Despite the worldwide efforts in understanding and combating the disease, many uncertainties remain, including the precise rates of transmission and mortality, not to mention the proper treatment, leading to concerns and confusion regarding the necessary duration of the isolation measures. The possible need to adopt intermittent strategies of social distancing has also been raised, alternating periods of stricter and looser isolation (Kissler et al., 2020) until the discovery of a vaccine or efficient treatment is made. Social isolation by itself leads to stress and negative mood (Brooks et al., 2020). The uncertainties mentioned above potentiate these effects, particularly in patients with a history of mental health disorders. Social isolation and loneliness are also associated with increased overall mortality (Steptoe et al., 2013), worse cardiovascular, and mental health outcomes (Leigh-Hunt et al., 2017) and cognitive decline (Evans et al., 2019). Furthermore, the recent Covid-19 outbreak has been associated with post-traumatic stress disorder (PTSD) symptoms, which were identified both in medical staff and the general population (Wang et al., 2020). Numerous studies have demonstrated how non-invasive neuromodulatory techniques such as rTMS and tDCS can help prevent and ameliorate stress, with effects not only on emotion, cognition, and behavior but also on the cardiovascular (Makovac et al., 2017) and autonomic nervous systems (Schestatsky et al., 2013). Although non-invasive, repetitive TMS is expensive and not portable (the only portable option applies a very short train of pulses). Therefore, it is not appropriate during the context of social isolation since patients would have to leave their homes to receive the treatment. On the other hand, tDCS is potentially portable, and its feasibility in home-based settings has been previously studied with promising results regarding its safety and effectiveness (Martens et al., 2018; Brietzke et al., 2020). Our objective in this short communication is to provide a comment on the potential tDCS application on preventing and treating stress-related symptoms during social isolation, while addressing the feasibility and efficacy of home-based tDCS.

Finite-time synchronization of stochastic complex networks with random coupling delay via quantized aperiodically intermittent control

This paper studies the finite-time synchronization issue of stochastic complex networks (SCNs) with random coupling delay and nonlinear coupling function. Internal delay, perturbation delay are also considered into this model. Meanwhile, a quantized aperiodically intermittent control strategy is proposed to realize finite-time synchronization of SCNs. By means of Lyapunov stability theory and graph theory, two types of sufficient conditions are derived to ensure finite-time synchronization of SCNs. The obtained results are closely related to the maximum proportion of rest width and the topological structure of considered networks. Moreover, the theoretical results is applied to study finite-time synchronization of stochastic coupled oscillators. Finally, a numerical example is presented to demonstrate the effectiveness and feasibility of the obtained results.

Intermittent Connectivity Maintenance With Heterogeneous Robots

In this article, we consider a scenario of cooperative task servicing, with a team of heterogeneous robots with different maximum speeds and communication radii, in charge of keeping the network intermittently connected. We abstract the task locations into a one-dimensional cycle graph that is traversed by the communicating robots, and we discuss intermittent communication strategies so that each task location is periodically visited, with a worst-case revisiting time. Robots move forward and backward along the cycle graph, exchanging data with their previous and next neighbors when they meet, and updating their region boundaries. Asymptotically, each robot is in charge of a region of the cycle graph, depending on its capabilities. The method is distributed, and robots only exchange data when they meet.

Characterization of moisture transfer during intermittent drying process for broccoli from LF-NMR experiments

Intermittent drying is considered as one of the alternative drying methods to save energy and improve product quality. In this study, low-field nuclear magnetic resonance (LF-NMR) has been used to evaluate the dynamics of the water mobility and distribution during the intermittent drying process. The results have shown that the first drying period of 1 hour is not effective to induce the moisture self-diffusion in the tempering period. After drying of 2 hours, the moisture transport in the tempering period became rapid and the changes reflected on T2 curve became visible clearly. The T2 values decreased gradually during drying, which indicated the reduced water mobility. As the tempering period progresses, the T2 continuously reduced and varied, which indicated the redistribution of water molecules during the tempering period. With the prolonged tempering time, the changes in T2 tended to be more stable, but it cannot reach equilibrium when there was concentration gradient. It was worth noting that A21 and A22 had an opposite trend during the intermittent drying process, indicating that the mobility of the bound water was increased during the intermittent drying. Effectively also when the samples were dried with the intermittent drying strategies, the vitamin C retention has increased by almost 50% relative to that of the continuous mode.

Adaptive synchronization of chaotic systems with time-varying delay via aperiodically intermittent control

The time-varying delay makes the state of a chaotic system more complex, which has a great influence on stability analysis and synchronization. To solve this problem, we utilize the method of adaptive intermittent control and the theory of Lyapunov stability to realize the synchronization of chaotic systems with time-varying delay. Firstly, we propose the control strategy to achieve the asymptotic exponential stability of the synchronous system under the aperiodically intermittent control. To make it easier to implement, we also propose a periodic intermittent control strategy. Finally, we choose the Lorenz and financial systems to do a numerical simulation. The experimental results verified the validity of our method.

Intermittent versus continuous enteral nutrition attenuates increases in insulin and leptin during short-term bed rest

PurposeTo compare endocrine responses to intermittent vs continuous enteral nutrition provision during short-term bed rest.MethodsTwenty healthy men underwent 7 days of bed rest, during which they were randomized to receive enteral nutrition (47%E as carbohydrate, 34%E as fat, 16%E as protein and 3%E as fibre) in a continuous (CONTINUOUS; n = 10; 24 h day−1 at a constant rate) or intermittent (INTERMITTENT; n = 10; as 4 meals per day separated by 5 h) pattern. Daily plasma samples were taken every morning to assess metabolite/hormone concentrations.ResultsDuring bed rest, plasma leptin concentrations were elevated to a lesser extent with INTERMITTENT vs CONTINUOUS (iAUC: 0.42 ± 0.38 vs 0.95 ± 0.48 nmol L−1, respectively; P = 0.014) as were insulin concentrations (interaction effect, P < 0.001) which reached a peak of 369 ± 225 pmol L−1 in CONTINUOUS, compared to 94 ± 38 pmol L−1 in INTERMITTENT (P = 0.001). Changes in glucose infusion rate were positively correlated with changes in fasting plasma GLP-1 concentrations (r = 0.44, P = 0.049).ConclusionIntermittent enteral nutrition attenuates the progressive rise in plasma leptin and insulinemia seen with continuous feeding during bed rest, suggesting that continuous feeding increases insulin requirements to maintain euglycemia. This raises the possibility that hepatic insulin sensitivity is impaired to a greater extent with continuous versus intermittent feeding during bed rest. To attenuate endocrine and metabolic changes with enteral feeding, an intermittent feeding strategy may, therefore, be preferable to continuous provision of nutrition.This trial was registered on clinicaltrials.gov as NCT02521025.

Optimal Threshold of Intermittent Maneuver for Target Observability Improvement

This study considers intermittent maneuver based on line-of-sight rate bounding to improve target observability for passive homing guidance. Target observability is critical for the performance of the target tracking filter and indirectly affects the guidance accuracy. This paper derives an observability measure associated with the Fisher information matrix for the adaptive intermittent maneuver strategy proposed in the previous studies. Then, the key parameters of the adaptive intermittent strategy are identified and optimized to maximize the observability measure. Numerical simulations demonstrate that the tracking filter performance is significantly improved. It is also confirmed that the guidance accuracy of proportional navigation is also improved by employing the adaptive intermittent maneuver strategy.

Cost–benefit analysis of surveillance for surgical site infection following caesarean section

ObjectiveTo estimate the economic burden to the health service of surgical site infection following caesarean section and to identify potential savings achievable through implementation of a surveillance programme.DesignEconomic model to...