Stability Of Networked Systems Research Articles

Quince seed mucilage/β-cyclodextrin/Mmt-Na+-co-poly (methacrylate) based pH-sensitive polymeric carriers for controlled delivery of Capecitabine

In current work, quince seed mucilage and β-Cyclodextrin based pH regulated hydrogels were developed using aqueous free radical polymerization to sustain Capecitabine release patterns and to overcome its drawbacks, such as high dose frequency, short half-life, and low bioavailability. Developed networks were subjected to thermal analysis, Fourier transforms infrared spectroscopy, powder x-ray diffraction, elemental analysis, scanning electron microscopy, equilibrium swelling, and in-vitro release investigations to assess the network system's stability, complexation, morphology, and pH responsiveness. Thermally stable pH-responsive cross-linked networks were formed. Nanocomposite hydrogels were prepared by incorporating Capecitabine-containing clay into the swollen hydrogels. All the formulations exhibited equilibrium swelling ranging from 67.98 % to 92.98 % at pH 7.4. Optimum Capecitabine loading (88.17 %) was noted in the case of hydrogels, while it was 74.27 % in nanocomposite hydrogels. Excellent gel content (65.88 %–93.56 %) was noticed among developed formulations. Elemental analysis ensured the successful incorporation of Capecitabine.Nanocomposite hydrogels released 80.02 % longer than hydrogels after 30 h. NC hydrogels had higher t1/2 (10.57 h), AUC (121.52 μg.h/ml), and MRT (18.95 h) than hydrogels in oral pharmacokinetics. These findings imply that the pH-responsive carrier system may improve Capecitabine efficacy and reduce dosing frequency in cancer therapy. Toxicity profiling proved the system's safety, non-toxicity, and biocompatibility.

Active Nodes for Passivity and Finite-Gain Stability of Non-autonomous Networks

This paper studies the role of a class of node systems with adjustable damping coefficients in the node dissipation inequalities, called the active nodes, for achieving passivity and finite-gain stability of network systems with external inputs and outputs. The paper first discusses the relation between the active nodes with passivity-type dissipation inequalities and those with L2-stability-type dissipation inequalities, especially focusing on how to transform one type into the other. Then, the paper proceeds to discuss the graph-theoretic condition on the locations of active nodes to achieve network passivity or finite-gain stability. Thereafter, a method for network reduction by exploiting active nodes is presented. Finally, a human-in-the-loop stabilization problem is solved for a network system by exploiting the results developed in the paper.

Cavitation Draft Tube Analysis of Francis Turbine Loads Variations: A Case Study from Cirata Hydropower Plant

Hydropower plant (PLTA) is a power plant of EBT (Renewable Energy), which utilizes water as a primary energy source. PLTA has a very important role in balancing the stability of network systems. In improving network system stability, hydropower is operated in a wide load range, frequent start-stop, and varying loads. Other functions are also as a buffer of peak load and back up system in case of interference in the network system. Francis turbine is the most widely used turbine and has a maximum efficiency of 93-95%. Problems related to the operation of hydropower are operational instability, cavitation, vortex breakdown, pressure shocks, vibration and noise that sometimes cause turbine system failure. In relation to the above conditions then in this thesis will be studied how the occurrence of cavitation due to variations loading. Case study conducted in this research is at Cirata hydropower plant with capacity of 126 MW per unit, which has type Francis turbine vertical shaft (variation of load starts 40% and 100%). The research method is done numerically, with modeling and flow simulation using ANSYS CFX 18.2. The results of this study show that at 40% load-operating conditions there is a very low-pressure area (under vapor pressure) and the emergence of a vortex rope that causes cavitation in the draft tube area, especially in the elbow region. While at 100% load operating conditions only slightly visible low-pressure area and no vortex rope appears.

Finite-Time Stability of Network Systems With Discontinuous Dynamics Over Signed Digraphs

This article investigates the finite-time stability (FTS) of network systems with discontinuous dynamics in the framework of signed networks. The sufficient criteria on the network interactive matrix are given to ensure the FTS of the considered systems in a unified framework. The explicit bound on the finite-time settling time is derived correspondingly. With the concept of Filippov solutions, the uniqueness of the nonsliding dynamics is shown, and the range of the sliding dynamics on the possible continuum of equilibria is given for the network systems with irreducible H-matrices. The obtained results are further applied to the network modulus consensus problems over signed digraphs. Several existing protocols are revisited and generalized with the proposed methods. Numerical examples are conducted to verify the theoretical results.

Stochastic Profit Maximization of Service Provider in Millimeter-Wave High-Speed Railway Networks

We study the problem of profit maximization for service providers using a newly emerged business model in millimeter-wave (mmWave) high-speed railway (HSR) networks. In such business model, a service provider purchases data transmission resource from a network operator with a low price. Then, mobile users only need to pay for requested services provided by the service provider. To optimize the profit of service provider, the profit analysis and optimization framework tailored toward the new business model and mmWave HSR networks is developed. This framework consists of three main components including admission control, transmission control, and resource purchasing control. To obtain optimal policies for these components, a stochastic profit optimization problem is formulated while taking into account differentiated service quality requirements, wireless transmission capacity, and network system stability. Then, the formulated problem is solved by using stochastic network optimization theory and stochastic profit maximization mechanism (SPMM) is established. An extensive performance evaluation of SPMM is conducted in order to demonstrate its superiority.

Partial-information-based consensus of network systems with time-varying delay via sampled-data control

In this paper, a novel decoupling method is introduced to investigate the consensus of network systems with partial coupling on the basis of sampling control. The novel method is enabled us to discuss channels of each node for network systems individually. By constructing several Lyapunov functionals and combining with free weighting approach, the stability of network systems with target node is analyzed. On the other hand, network systems with time-varying delay are considered. Based on Fourier theory, an alternative inequality is presented, which is more precise than the Wirtinger inequalities. This inequality encompasses the Jensen one and leads to manageable linear matrix inequalities conditions (LMIs). Therefore, the consensus of network systems with time-varying delay can be guaranteed. Through two illustrated examples, the effectiveness of the proposed method is demonstrated sufficiently.

Multiple Moving Targets Surveillance Based on a Cooperative Network for Multi-UAV

With the development of better links, enhanced coverage, comprehensive data resources, and network system stability, the cooperative network formed by wireless sensor networks and unmanned aerial vehicles is envisioned to provide immediate and long-term benefits in military and civilian fields. Previous works mainly focus on how to use UAVs to assist WSNs in sensing and data collection jobs, or target localization with a single data source in surveillance systems, while the potential of multi-UAV sensor networks has not been fully explored. To this end, we propose a new cooperative network platform and system architecture of multi-UAV surveillance. First we propose the design concepts of a multi- UAV cooperative resource scheduling and task assignment scheme based on the animal colony perception method. Second, we provide the moving small target recognition technique and localization and tracking model using the fusion of multiple data sources. In addition, this article discusses the establishment of suitable algorithms based on machine learning due to the complexity of the monitoring area. Finally, experiments of recognition and tracking of multiple moving targets are addressed, which are monitored by multi- UAV and sensors.

Stability and stabilisation of a class of networked dynamic systems

ABSTRACTWe investigate the stability and stabilisation of a linear time invariant networked heterogeneous system with arbitrarily connected subsystems. A new linear matrix inequality based sufficient and necessary condition for the stability is derived, based on which the stabilisation is provided. The obtained conditions efficiently utilise the block-diagonal characteristic of system parameter matrices and the sparseness of subsystem connection matrix. Moreover, a sufficient condition only dependent on each individual subsystem is also presented for the stabilisation of the networked systems with a large scale. Numerical simulations show that these conditions are computationally valid in the analysis and synthesis of a large-scale networked system.

A Typical Power Allocation for Distributed Filtering

In this paper, the problem of power allocation is considered for distributed estimation over a sensor network with limited power. An online power allocation scheme is introduced to optimize the power consumption, where the power distributed to each communication channel depends on the innovation value of the sender. First, an optimal estimator gain is designed for each sensor by minimizing the mean-squared estimation error covariance. Second, a sufficient condition is provided to guarantee the stability of networked system with online power allocation scheme. Finally, we compare the estimation performance of the proposed online power scheduling scheme with some typical offline power scheduling schemes.

Instantaneous protection scheme for backup protection of high-voltage transmission lines

The protection scheme focused on in this study is a typical protection system used in high-voltage systems such as 132 kV, 275 kV, and 500 kV. The research will analyze the existing protection scheme for transmission lines that the power utility has implemented and will propose a new protection scheme to improve the performance of the existing scheme. The existing protection scheme currently implemented by the power utility for backup protection operation has a longer fault-clearing time and no restoration time, and it does not utilize support relays. This study will focus on a backup protection operation on high-voltage overhead transmission lines, which take up communication when the main protection has failed to communicate, the relay has failed due to loss of DC supply, or the relay function itself has been blocked. Moreover, all the support relays will be utilized in order to improve the protection system. The improvement will consider three elements, which are the fault-clearing time, fast restoration time, and relay utilization. Each improvement to the protection system will have its own philosophy and concrete rationale, which have advantages or disadvantages for the transmission line. The effect of the improvement scheme will also consider the outcomes in other schemes to ensure that time coordination does not overlap. Every possibility of a fault will be analyzed in order to have a clear understanding of the effects of the three elements. CAPE software will be used as a tool for simulation and to analyze its compatibility with real applications. CAPE software is able to model a real-life transmission line and is also able to simulate faults in the tested area. The results of the simulation show that the backup protection operation improved fault-clearing time and restoration time. It also increased the network's system stability, particularly during the occurrence of maximum fault currents.

Assessing the stability of the LNG supply in the Asia Pacific region

The Asia Pacific (AP) region has experienced huge growth in the use and trade of LNG during the last decade, which is a reflection of the overall region’s policies towards low-carbon development. Japan, South Korea, Mainland China, Taiwan and India (JKCTI) are the top five importers and consumers of LNG in the world. A holistic network system stability indicator, considering various risk factors, has been constructed based on ecological network analysis (ENA) to assess the stability of LNG supplies in each of the JKCTI countries and in the overall AP region. The research revealed that the increase in the number of LNG suppliers and improvements (higher values) of the risk factors have enhanced the status of the stability of LNG supplies. A comparative ranking of the overall levels of natural gas supply security was estimated and found that Mainland China is the leader within the AP region, followed by India, Japan, South Korea and Taiwan. Furthermore, the reliability of the LNG suppliers in terms of sharing their maximum LNG supplying capacity in each of the JKCTI countries and AP region was also estimated.

Synchronization Problem and Stability of Network Systems

Synchronization Problem and Stability of Network Systems

Feedback Stabilization of Networked Systems over Fading Channels with Resource Allocation

In this paper, we consider the stabilization problems for networked control systems (NCSs) over parallel independent communication channels, wherein each channel is modeled as a general fading channel, i.e., a combination of multiplicative noise and additive noise. A channel capacity notion is introduced for such general fading channels to represent their capabilities of information transmission. A necessary and sufficient condition for closed-loop stabilization with stationary signal-to-noise ratio (SNR) constraints is established which builds a bridge between the channel capacities and the topological entropy of the open-loop plant. When the condition holds, a channel-controller co-design approach is proposed to accomplish the stabilization. Finally, a numerical example is presented to verify the effectiveness of our results.

Real Time Network Traffic Monitoring Using FPGA

In computer networks, network traffic measurement is the process of measuring the amount and type of traffic on a particular network. This is especially important with regard to effective bandwidth management. Hence more sophisticated network traffic monitoring and analysis tools are in need in order to maintain the network system stability and to fix network problems on time or to avoid network failure. Considering this need we propose Field programmable gate array (FPGA) architecture for network flow analysis. A decision tree algorithm is also proposed for flow classification. The designed architecture is tested against various real time traffic models created using probability distribution technique. The performance evaluation of this architecture proves that it support the network traffic stream at multi giga bit rate which is better than most of the existing software techniques.

On the stability of networked impulsive control systems

SUMMARYIn this paper, the stability of linear networked impulsive control systems is studied. The data dropout rate over N steps (DRNS) is defined, and the maximal allowable DRNS is computed, which provides a guideline for the system stability in the sense that, if the actual DRNS is less than this maximal value, then the system is asymptotically stable. To handle the network‐induced delays, a propagation unit based on the system model is introduced to the system. A necessary and sufficient condition for the asymptotical stability of the networked system with the propagation unit is derived. Furthermore, networked linearized impulsive control systems suffering from both transmission delays and data dropouts are also investigated. To design proper impulsive controllers for such systems, some algorithms are further proposed based on LMI techniques and V‐K iteration approaches. Finally, numerical examples are presented to illustrate the theoretical results. Copyright © 2011 John Wiley & Sons, Ltd.

Stabilization of Networked Systems under Information Structure Constraints

The objective of this paper is to propose a systematic approach to decentralized stabilization with sampled-data delayed feedback for basic models of networked continuous-time complex systems. Single-packet transmissions and multiple-packet transmissions are considered for the I/O-oriented systems as well as the interconnected systems with disjoint structure of subsystems and their interconnections. The Liapunov-Razumikhin based method is used. An attention is focused on the effect of data-packet dropout and communication delays between the plant and the controller to design stabilizing decentralized controllers. It is shown how this methodology can lead to a decentralized control design with time-varying delays in the input. For such a purpose, a delay-dependent approach is considered in order to obtain decentralized controllers asymptotically stabilizing closed-loop networked control systems.

The Problem of Stabilization of Networked Systems under Computational Power Constraints

The paper considers stabilization under communication errors and limited data rate by means of realistic controllers with bounded (as time progresses) computational powers. Discrete-time partially observed noisy linear systems are studied for which the sensor signals are communicated to the controller over a finite capacity stochastic digital link. Addressed is stabilization in probability. It is shown that stability cannot typically be achieved by means of a finite memory decoder-controller so far as the boundary of the corresponding stabilizability domain is given by the zero-error capacity of the channel, which is typically zero. At the same time, stability can be achieved with keeping the expected values of the consumed computational resources bounded: the boundary of the domain where stabilization can be ensured by a coder and decoder with bounded expected computational powers is given by the ordinary Shannon capacity of the noisy channel.