Synchronization Time Research Articles

A Novel Channel Errors Calibration Algorithm for Multichannel High-Resolution and Wide-Swath SAR Imaging

For a spaceborne high-resolution and wide-swath synthetic aperture radar (HRWS-SAR) system, it usually uses the digital beamforming technology. However, in practice, because of the influences of temperature, antenna pattern, receiving antenna, and other error factors, there may exist the range synchronization time errors, amplitude errors, and phase errors among different spatial channels. These nonideal factors will significantly degrade the multichannel data reconstruction performance, resulting in a smeared SAR image. To address this issue, in this article we propose a novel channel error correction algorithm based on the orthogonal projection theory. First, the optimal weight of each Doppler ambiguity component is calculated by the orthogonal projection. Then, the cost function is constructed based on the power maximization criterion, from which the channel phase errors can be obtained. Finally, the HRWS-SAR imaging can be finely realized after performing the channel balancing. Compared with the conventional phase error estimation method, the proposed algorithm does not require to perform the matrix eigenvalue decomposition, avoiding the signal leakage phenomenon under low SNR case. The effectiveness of the proposed algorithm is validated by both airborne and space-borne real SAR data.

FPGA Realization of Two Different Fractional- Order Time-Delay Chaotic System With Predefined Synchronization Time

FPGA Realization of Two Different Fractional- Order Time-Delay Chaotic System With Predefined Synchronization Time

Context Aware Data Synchronization in Ubiquitous Networks: Cognitive Agent Approach

Ubiquitous networks comprise a diverse set of homogeneous or heterogeneous networks to perform ubiquitous computing operations. In the real-time application context, users can access data from any place and at any time by using mobile devices/nodes such as computer/laptop, mobile, tablet and so on. Nowadays, mobile computing paradigms have an impact on the spread of mobile computing devices, resulting in the transmission of data across ubiquitous networks. To avoid uncertainty, it is critical to maintain data consistency across all devices. This research work has proposed a context aware data synchronization using cognitive agents as a case study on shopping environments. The proposed data synchronization scheme detects network changes, resolves any potential conflicts, and updates various synchronizing devices with different device attributes. Cognitive agents are used to track the data across multiple devices. Context aware ubiquitous networks respond to customer requests based on their personal profiles, which often include individual preferences while considering the technological restrictions of the mobile device and the context of operating environment. The proposed work is compared with other existing methods in terms of data accuracy, data synchronization time, and computation and communication overhead.

Managing during the crisis: Factors coming from inside the society

This study summarizes the arguments and counter-arguments within the scientific debate on the welfare state issue. After the years of development of the welfare state caused by the development of the economy in the post-war years, when social rights became a new form of property, the 1970s came a period of economic crisis. The welfare state crisis comes with the economic crisis and is criticized by both the right and left of the political spectrums. This research checks whether changes in the labor market caused by the workforce transition from the environment of production to the environment of services greatly affect individuals and families. The research subject is labor migration and an increase in employment in the service sector versus a decrease in employment in the production sector caused by the arrival of the fourth and, according to some experts, the fifth industrial revolution. Other factors that are the subject of the research and are responsible for the crisis of the welfare state are the family crisis and the population’s aging. These factors individually do not threaten the functioning of the welfare state, but as a complex that creates a load in a common and synchronous time frame, they are highly dangerous for the welfare state. The main goal of this research is to point out the most serious factors coming from within a society that affects the functioning of the welfare state. The literature analysis on the welfare state, social economics, social policy, and labor migration confirmed the enormous increase in pressure on the welfare state in the last two decades. This study deals with the idea of the complete demise of the welfare state when multinational insurance companies take over its function. Another option is supplementing or replacing some parts of the welfare state with another alternative. Such an alternative is shown, for example, by the measures that were used during the C-19 pandemic in the Slovak Republic. This is mainly about the financial aid that the state distributed to entrepreneurs who were forced to suspend the operation of their businesses due to the pandemic. Such assistance had many common denominators with the Unconditional Basic Income project, which is increasingly popular in the world and is proving to be a suitable supplement to the social system and a supplement to the welfare state. The results of study could be useful both for student practice and social and scientific fields. At the end of the research, the study is dedicated to finding a solution to help the welfare state in the given situation.

Subclinical ketosis as a factor reduction of reproductive indicators of high productive cows

Purpose: The aim of the research is to study the effect of subclinical ketosis (SCK) on the effectiveness of artificial insemination of highly productive dairy cows in the postpartum period.Materials and methods. The studied animals were selected according to the principle of conditional analogs and were divided into 2 groups of 6 animals each. Group 1 - animals with a blood concentration of 3- hydroxybutyrate˂ 1.0 mmol / l, group 2 - animals with subclinical ketosis with a concentration of 3-hydroxybutyrate in the blood in the range of 1.0-1.4 mmol / l. Blood was collected from animals on the 5th, 15th and 33-35th days after calving. In the obtained blood serum samples, the content of total protein, albumin, urea, glucose, cholesterol, triglycerides, calcium, phosphorus, magnesium, creatinine, total bilirubin, the activity of transaminase enzymes and alkaline phosphatase was determined. The concentration of steroid hormones has been determined. Before artificial insemination, the animals were synchronized according to the pressinovsinh scheme.Results. Most of the biochemical blood parameters did not go beyond the reference values. By the time of hormonal stimulation of sexual heat in cows with SCK, a decrease in 3-hydroxybutyrate (˂ 1,0 mmol / l) and an increase in glucose (> 3.0 mmol / l) were recorded. On the 15th day after calving, in the group with SCK, there was an increase in total bilirubin, cholesterol, triglycerides, and magnesium (p˂ 0,01). On the 15th day after calving, testosterone levels were 13% higher in the SCK group. By the time of synchronization, the level of progesterone in the group of animals with SCK was lower in comparison with the control group. In the group of animals with SCK, the lowest reproductive indices were recorded: the insemination index in the group with SSC was higher by 46%, the service period was 49 days longer, the interbody period was significantly longer by 68 days (p˂ 0,05).Conclusion. Subclinical ketosis, recorded on the 15th day after calving, helps to reduce the reproductive performance of high -yielding dairy cows. Normalization of the concentration of 3-hydroxybutyrate from subclinical to physiologically normal values, and subsequent hormonal synchronization do not reduce this negative effect of SCK.

Fast synchronization of symmetric Hénon maps using adaptive symmetry control

The article discusses the possibility of synchronizing adaptive discrete chaotic maps through the control of the symmetry coefficient. Since a change in the symmetry coefficient in symmetric chaotic maps possesses a much less influence on the system oscillation mode than a change in nonlinearity parameters, we assume that the synchronization of such systems can be achieved in a small number of iterations. To experimentally examine this hypothesis, we studied three cases of adaptive synchronization feedback controllers for the conventional Hénon map and adaptive Hénon map. We found that synchronization occurs faster while the symmetry coefficient is controlled by comparing the synchronization times in all considered cases. Averagely, an accurate estimate of the adaptive coefficient is achieved after 3–5 iterations. Applying this approach to the communication systems based on modulation through switching parameters of chaotic systems can significantly reduce the transient processes inherent in this method. The numerical experiments show that it is possible to decrease the transmission time by more than 25%, even in the case of short messages.

Cross-cultural Analysis of Main Economic Partners of the Republic of Moldova

The paper represents a comparative study of national culture features of the main commercial partners of the Republic of Moldova and the countries preferred by Moldovan citizens to emigrate: Romania, Russia, Italy and Germany. The research focused on two cultural bipolar models: Hofstede, which comprises six cultural dimensions: individualism vs. collectivism, power distance, uncertainty avoidance, masculinity vs. femininity, long-term vs. short-term orientation, indulgence vs. restraint, and Trompenaars-Hampden-Turner, which contains seven dimensions: universalism vs. particularism, individualism vs. communitarianism, neutral vs. emotional, specific vs. diffuse, achievement vs. ascription, sequential time vs. synchronous time, internal vs. external control. The established similarities and differences, knowledge of cultural specificity in international interactions, both social and economic, is an added value for individuals to successfully integrate and fit into a society, other than their native, and for businesses to be successfully managed on international level.

Fixed/Preassigned-time synchronization of quaternion-valued neural networks via pure power-law control

The fixed-time synchronization and preassigned-time synchronization of quaternion-valued neural networks are concerned in this article. By developing fixed-time stability and proposing a pure power-law control scheme, some simple conditions are obtained to realize fixed-time synchronization of quaternion-valued neural networks and the upper bound of the synchronized time is provided. Furthermore, the preassigned-time synchronization of quaternion-valued neural networks is investigated based on pure power-law control design, where the synchronization time is preassigned in advance and the control gains are finite. Note that the designed controllers in this paper are the pure power-law forms, which are simpler and more effective compared with the traditional design composed of the linear part and power-law part. Eventually, an example is given to illustrate the feasibility and validity of the results obtained.

Fixed-Time Synchronization Control of Delayed Dynamical Complex Networks.

Fixed-time synchronization problem for delayed dynamical complex networks is explored in this paper. Compared with some correspondingly existed results, a few new results are obtained to guarantee fixed-time synchronization of delayed dynamical networks model. Moreover, by designing adaptive controller and discontinuous feedback controller, fixed-time synchronization can be realized through regulating the main control parameter. Additionally, a new theorem for fixed-time synchronization is used to reduce the conservatism of the existing work in terms of conditions and the estimate of synchronization time. In particular, we obtain some fixed-time synchronization criteria for a type of coupled delayed neural networks. Finally, the analysis and comparison of the proposed controllers are given to demonstrate the validness of the derived results from one numerical example.

Robust global fixed-time synchronization of different dimensions fractional-order chaotic systems

This paper addresses the problem of global fixed-time synchronization of two fractional chaotic systems with different dimensions in the presence of matched bounded and differentiable exogenous disturbances and uncertainties in the systems. Firstly, a novel fixed-time stable dynamical system is investigated wherein the upper bound estimate of the settling time of synchronization is determined by a priori value dependent on a design parameter regardless of the initial conditions. The introduced dynamical system to guarantee fixed-time stability is completely different from that in the existing works of literature. Based on the introduced fixed-time dynamic, a novel controller is designed that guarantees globally synchronization of two fractional chaotic systems with different dimensions within the fixed-time. Afterward, the result of synchronization of two different dimensional fractional chaotic systems within the fixed-time is extended to the networked ones. Finally, the effectiveness and validity of the results of the theoretical analysis are demonstrated by the illustrative examples and their numerical simulations.

Curriculum to Develop Documentation Proficiency Among Medical Students in an Emergency Medicine Clerkship.

IntroductionDocumenting a clinical encounter is a core skill for entering residency, but medical students often receive scant dedicated documentation training, leading to a high rate of inadequate information. Utilizing adult experiential learning theory, we created and implemented an educational resource to train medical students on how to proficiently document an emergency department (ED) patient encounter.MethodsOne hundred and five third- and fourth-year medical students participating in an emergency medicine clerkship took part in a brief orientation day documentation curriculum that included a group didactic, a review of reference materials, a standardized patient activity, a sample patient note writing assignment with individualized feedback, and supervising faculty physician feedback on real patient notes. Students were subsequently entrusted with primary documentation responsibility for all ED patients whose care they participated in.ResultsAfter completing this curriculum, students’ self-rated comfort with writing a high-quality note increased from 4.1 to 5.9 (p < .001) and knowledge about billing and coding increased from 2.9 to 5.5 (p < .001) on a 7-point scale. Among faculty physicians, 93% found student notes to always, usually, or frequently be clinically useful, and 86% reported that student notes always, usually, or frequently contained enough information for billing and coding.DiscussionThis curriculum was effective at training medical students on proficient patient care documentation in emergency medicine. The relatively short amount of synchronous learning time required could aid in implementation, and the allowance of medical student notes to count for billing purposes could facilitate student and faculty buy-in.

Altered Dynamic Brain Connectivity in Individuals With Sickle Cell Disease and Chronic Pain Secondary to Hip Osteonecrosis.

Individuals with sickle cell disease (SCD) exhibit changes in static brain connectivity in rest. However, little known as chronic pain associated with hip osteonecrosis affects dynamic brain connectivity during rest and the motor imagery task. The aim of this study was to investigate the characteristics of the dynamic functional brain connectivity of individuals with SCD and chronic pain secondary to hip osteonecrosis. This is a cross-sectional study comparing the dynamic brain connectivity of healthy individuals (n = 18) with the dynamic brain connectivity of individuals with SCD and chronic pain (n = 22). Individuals with SCD and chronic pain were stratified into high- or low-intensity pain groups based on pain intensity at the time of assessment. Dynamic brain connectivity was assessed through electroencephalography in 3 stages, resting state with eyes closed, and during hip (painful for the SCD individuals) and hand (control, nonpainful) motor imagery. Average weight of the edges and full synchronization time (FST)-time required for 95% of the possible edges to appear over time during a given task-were evaluated. Regarding the average weight of the edges, individuals with SCD and high-intensity pain presented higher edge weight during hip motor imagery. The average weight of the edges correlated positively with pain intensity and depression symptoms. Individuals with SCD and chronic pain complete the cerebral network at rest more quickly (lower FST). Individuals with SCD and chronic pain/hip osteonecrosis have impaired dynamic brain network with shorter FST in rest network and more pronounced diffuse connectivity in individuals with high-intensity pain. The dynamic brain network evaluated by time-varying graphs and motif synchronization was able to identify differences between groups.

Fractional-order discontinuous systems with indefinite LKFs: An application to fractional-order neural networks with time delays

In this article, we discuss bipartite fixed-time synchronization for fractional-order signed neural networks with discontinuous activation patterns. The Filippov multi-map is used to convert the fixed-time stability of the fractional-order general solution into the zero solution of the fractional-order differential inclusions. On the Caputo fractional-order derivative, Lyapunov-Krasovskii functional is proved to possess the indefinite fractional derivatives for fixed-time stability of fragmentary discontinuous systems. Furthermore, the fixed-time stability of the fractional-order discontinuous system is achieved as well as an estimate of the new settling time.. The discontinuous controller is designed for the delayed fractional-order discontinuous signed neural networks with antagonistic interactions and new conditions for permanent fixed-time synchronization of these networks with antagonistic interactions are also provided, as well as the settling time for permanent fixed-time synchronization. Two numerical simulation results are presented to demonstrate the effectiveness of the main results

The Features of the Reference Frame Concomitant to the Cosmic Microwave Background

The features of reference frame, concomitant to the cosmic microwave background, immobile relatively cosmic microwave background, are considered. It is shown that the features of reference frame, concomitant to the cosmic microwave background (CMB), are determined by its properties. Any other object in the Universe and reference frame concomitant to it, is immersed in the CMB and moves relative to the reference frame concomitant to microwave background radiation. The zero pecular velocity of the reference frame concomitant to the microwave background radiation is analogous to the zero temperature on the Kelvin scale. Time in it is most rapid in relation to the time in any other reference frame, observable and measurable in any of them. The features of time, pecular speed, relative speed of two inertial RF, stellar aberration, and Doppler effect in the reference frame concomitant to the microwave background radiation are considered. According to the determined relative velocity of the two reference systems and the peculiar velocity of the reference system with the observer, the components of their relative velocity are determined. Determining the components of the relative velocity of the reference frames with determining the synchronous time for all points at any time in the reference frame concomitant to microwave background radiation, allows us to investigate the possibility of determining the speed of light "one way" and using it to navigate vehicles in distant space. Stability of angular location of heterogeneities of CMB in reference frame concomitant to CMB, allows us to use these heterogeneities for the increase of exactness of astronomic reference frames HCRF and ICRF.

Fixed-time synchronization of memristor chaotic systems via a new extended high-gain observer

Memristor based chaotic oscillators are often chosen for secure communication owing to their interesting feature. In chaos-based secure communication applications, synchronization is a central issue. Most of synchronization methods proposed in the literature are asymptotic. In practice, it is desirable that synchronization be established in a user predefined time. This paper provides new developments in the design of filtered extended high-gain observer dedicated for prescribed-time synchronization of memristor chaotic systems used in a master-slave based secure communication process subject to channel noise. The proposed prescribed-time extended filtered-high gain observer is constructed on the basis of a time-dependent coordinates transformation based on modulating functions which annihilate the effect of initial conditions on the synchronization time. Simulations performed on a numerical example illustrate the efficiency of the proposed approach.

SECURE COMMUNICATION USING THE SYNCHRONIZATION OF TWO FRACTIONAL-ORDER CHAOTIC SYSTEMS WITH ORDER CHANGES USING THE FINITE-TIME OPTIMAL CONTROL APPROACH

In this paper synchronization problem for two different fractional-order chaotic systems has been investigated. Based on fractional calculus, optimality conditions for this synchronization have been achieved. Synchronization Time and control signals are two factors that are optimized. After that, the synchronization method is applied in secure communication. Finally using the simulation example, the performance of the proposed method for synchronization and chaotic masking is shown.

Relativistic Fractional-Dimension Gravity

This paper presents a relativistic version of Newtonian Fractional-Dimension Gravity (NFDG), an alternative gravitational model recently introduced and based on the theory of fractional-dimension spaces. This extended version—Relativistic Fractional-Dimension Gravity (RFDG)—is based on other existing theories in the literature and might be useful for astrophysical and cosmological applications. In particular, in this work, we review the mathematical theory for spaces with non-integer dimensions and its connections with the non-relativistic NFDG. The Euler–Lagrange equations for scalar fields can also be extended to spaces with fractional dimensions, by adding an appropriate weight factor, and then can be used to generalize the Laplacian operator for rectangular, spherical, and cylindrical coordinates. In addition, the same weight factor can be added to the standard Hilbert action in order to obtain the field equations, following methods used for scalar-tensor models of gravity, multi-scale spacetimes, and fractional gravity theories. We then apply the field equations to standard cosmology and to the Friedmann-Lemaître-Robertson-Walker metric. Using a suitable weight vtt, depending on the synchronous time t and on a single time-dimension parameter αt, we extend the Friedmann equations to the RFDG case. This allows for the computation of the scale factor at for different values of the fractional time-dimension αt and the comparison with standard cosmology results. Future additional work on the subject, including studies of the cosmological late-time acceleration, type Ia supernovae data, and related dark energy theory will be needed to establish this model as a relativistic alternative theory of gravity.

Finite‐time and fixed‐time synchronization of fuzzy Clifford‐valued Cohen‐Grossberg neural networks with discontinuous activations and time‐varying delays

SummaryIn this article, we are concerned with fuzzy Clifford‐valued Cohen‐Grossberg neural networks (FCVCGNNs) via discontinuous activations and time‐varying delays. First, the time‐delayed feedback strategy is used to investigate the synchronization in finite‐time and fixed‐time of FCVCGNNs with discontinuous activations and time‐varying delays. By designing Lyapunov functions and utilizing differential inequalities, several effective conditions are derived to ensure synchronization in finite‐time and fixed‐time of the addressed neural networks. A novel fixed‐time convergence method is proposed to study synchronization in fixed‐time of discontinuous delayed FCVCGNNs. Furthermore, the settling time of synchronization are estimated. In the end, two numerical examples with simulations are given to confirm the effectiveness of the synchronization criteria.

Climatic Drivers of Deglacial SST Variability in the Eastern Pacific

AbstractWe explore the response of northeastern Pacific sea surface temperature (SST) to deglacial (16–7 ka) climate variability as recorded in ‐based SST reconstructions spanning 65°N to 10°S. Included in the analysis is a new 23 kyr SST record from core NH8P from the northwest Mexican Margin. We isolate spatiotemporal patterns in regional SSTs with trend empirical orthogonal function (TEOF) analysis. The dominant TEOF mode reflects deglacial warming associated with rising . Tropical and subtropical SSTs correlated most strongly with this mode, suggesting that the thermodynamic response of the tropical eastern Pacific to greenhouse gas forcing was the dominant driver of regional SST change during deglaciation. The second TEOF mode reflects millennial‐scale variability and is most strongly expressed in subpolar SSTs. The synchronous timing between North Pacific and North Atlantic SST oscillations is evidence for the rapid transmission of millennial‐scale climate perturbations between the basins, likely through an atmospheric teleconnection. SSTs at NH8P have no correlation with either leading TEOF mode as there is minimal change in SST at this site after 20 ka. A model simulation of the LGM indicates that glacial cooling was muted in much of the Eastern Pacific Warm Pool (EPWP), in which NH8P lies, due to reductions in latent heat flux. This suggests that the wind‐evaporation‐SST feedback was responsible for the attenuation of EPWP cooling. Overall, this study highlights the distinct latitudinal trends in the Pacific's response to deglaciation.

Finite/Fixed-Time Synchronization of Multi-Layer Networks Based on Energy Consumption Estimation

This paper discusses finite/fixed-time (FNT/FXT) synchronization of multi-layer networks based on energy consumption estimation. Firstly, a novel FXT stability theorem of dynamical system is presented. Secondly, sufficient criteria for FNT/FXT synchronization in multi-layer networks are given, and the estimation of the energy consumption are also gained. Especially, the range of the number of layers of network is gained based on the least convergence time and the estimation of the least energy consumption. The results show that shorter synchronization time and less energy consumption does not mean less network layers. Finally, the validity of the theoretical method is verified by numerical simulation.