Inhomogeneous Node Research Articles

Tail Prediction for Heterogeneous Data Center Clusters

Service providers need to meet their service level objectives (SLOs) to ensure better client experiences. Predicting tail sojourn times of applications is an essential step to combat long tail latency. Therefore, as an attempt to further unravel the power of our prediction model, new study scenarios for heterogeneous environments will be introduced in this research by using either of two methods: white- or black-box solutions. This research presents several techniques for modeling clusters of inhomogeneous nodes. Those techniques are recognized as heterogeneous fork-join queuing networks (HFJQNs). Moreover, included in the research is a nested-event-based simulation model, borrowing help from multi-core technologies. This model adopts the multiprocessing technique to take part in its design to enable different architectural designs for all computing nodes. This novel implementation of the simulation model is believed to be the next logical step for research studies targeting heterogeneous clusters in addition to the several provided scenarios. Experimental results confirm that even with the existence of such heterogeneous conditions, the tail latency can be predicted at high-load regions with an approximated relative error of less than 15%.

Experimental Realization of Two-Dimensional Weak Topological Insulators.

We report the experimental realization of a two-dimensional (2D) weak topological insulator (WTI) in spinless Su-Schrieffer-Heeger circuits with parity-time and chiral symmetries. Strong and weak topological indexes are adopted to explain the experimental findings that a Dirac semimetal (DSM) phase and four WTI phases emerge in turn when we modulate the centrosymmetric circuit deformations. In the DSM phase, it is found that the Dirac cone is highly anisotropic and that it is not pinned to any high-symmetry points but can widely move within the Brillouin zone, which eventually leads to the phase transition between WTIs. In addition, we observe a pair of flat-band domain wall states by designing spatially inhomogeneous node connections. Our work provides the first experimental evidence for 2D WTIs, which significantly advances our understanding of the strong and weak nature of topological insulators, the robustness of flat bands, and the itinerant and anisotropic features of Dirac cones.

Spiral Waves in a Lattice Array of Josephson Junction Chaotic Oscillators with Flux Effects

Josephson junction devices play a significant role in various physical nonlinear systems because of their complex characteristics. Chaotic phenomenon in various types of Josephson junction devices has been widely reported, but many of those literature studies exempted the analysis into multistability and megastability features of the device. In this work, we investigate the network behaviour using a type of Josephson junction-memristor (JJM) device considering the feedback flux effects while modelling. We have considered both AC- and DC-type external excitation currents, and while considering the AC excitation, the system shows megastability (Ramakrishnan et al. 2020). When analysing the lattice layer network constructed with JJM excited by DC bias current, the network shows a turbulent behaviour thus forming spiral waves. This was not the case when we applied AC bias current for which the network showed a much pattern-like formation confirming localised areas of energy distribution. This energy distribution is due to the homogeneous states of the local nodes which are correlated by the respective periodicity plots. When we apply AC bias current with very low frequency, the network shows small areas of local spirals which are soon dissipated by the inhomogeneous nodes nearby. Thus, we could show that the external bias current plays an important role in the collective performance of the Josephson junction devices.

In the Way of having an Optimum Wireless Ad-Hoc Sensor Networks: Analysis of Deploying Homogeneous and Inhomogeneous Nodes

In the Way of having an Optimum Wireless Ad-Hoc Sensor Networks: Analysis of Deploying Homogeneous and Inhomogeneous Nodes

Asymptotic Analysis of Inhomogeneous Information-Centric Wireless Networks With Infrastructure Support

The information-centric networking (ICN) is a promising and significant approach towards the host-to-content interaction. Motivated by the fact that nodes are inhomogeneously distributed to a certain extent in wireless networks, e.g., the distribution of vehicles exhibits cluster phenomenon in some bustling places of urban areas, we study the impacts of inhomogeneous node distribution and local node cooperation on information-centric wireless networks with infrastructure support. The distribution of nodes is assumed to be inhomogeneous as a multiclustering topology. The base stations are assumed to have access to all the contents, which are requested following a popularity distribution. We propose a scheme where each node retrieves the requested content from other nodes or base stations. Based on the number of clusters and that of base stations, we divide the network topology into two cases, i.e., the cluster-dense case and cluster-sparse case, and evaluate the corresponding throughput and delay performance. Finally, under the Zipf's law for content popularity distribution, we investigate the optimal caching problem in the two cases, and obtain the optimized throughput and delay performance.

Impacts of Social Relationships and Inhomogeneous Node Distribution on the Network Performance

This paper studies the impacts of social relationships and inhomogeneous node distribution on wireless network performance. Motivated by the social characteristic that makes nodes more likely to communicate with nearby nodes, we present a model that captures the small-world property, power-law distribution, and multi-clustering topology of wireless networks. We compute the average traffic distance to derive the optimal per-node capacity, which is then analyzed from the social perspective. Based on the communication pattern, we introduce the quasi-strong ties and quasi-weak ties in order to discover how system parameters control the amount of network flows with different strengths of social relationships. Moreover, we propose an indicator of information propagation speed (IIPS), and show that there is a tradeoff between the IIPS and the per-node capacity of overall nodes.

Network Connectivity With Inhomogeneous Correlated Mobility

In this paper, we derive the critical transmission range, i.e., the smallest transmission distance of nodes such that wireless network can be connected, in large-scale clustered wireless networks. Contrary to most previous literature on independent and homogeneous mobility of nodes, we consider general settings with inhomogeneous node distribution and correlated mobility. In particular, we consider three network states based on the degree of correlation among nodes, i.e., cluster-sparse state (strong correlations), cluster-dense state (weak correlations), and cluster-transitional state (medium correlations). Under each state, we focus on the following problems: 1) how to place cluster-head nodes to minimize the critical transmission range and 2) what is the corresponding minimum critical transmission range. We derive the optimal distribution of cluster-head nodes that minimizes the critical transmission range, and show that the inhomogeneous distribution of mobile nodes leads to a smaller critical transmission range.

Time‐domain vector potential technique for the meshless radial point interpolation method

SummaryA time‐domain meshless algorithm based on vector potentials is introduced for the analysis of transient electromagnetic fields. The proposed numerical algorithm is a modification of the radial point interpolation method, where radial basis functions are used for local interpolation of the vector potentials and their derivatives. In the proposed implementation, solving the second‐order vector potential wave equation intrinsically enforces the divergence‐free property of the electric and magnetic fields. Furthermore, the computational effort associated with the generation of a dual node distribution (as required for solving the first‐order Maxwell's equations) is avoided. The proposed method is validated with several examples of 2D waveguides and filters, and the convergence is empirically demonstrated in terms of node density or size of local support domains. It is further shown that inhomogeneous node distributions can provide increased convergence rates, that is, the same accuracy with smaller number of nodes compared with a solution for homogeneous node distribution. A comparison of the magnetic vector potential technique with conventional radial point interpolation method is performed, highlighting the superiority of the divergence‐free formulation. Copyright © 2015 John Wiley & Sons, Ltd.

Absorbing boundary conditions: a spectral collocation approach

SUMMARYWe introduce a spectral collocation method for the discretisation of the shallow water equations on a one‐dimensional semi‐infinite domain, employing scaled Laguerre basis functions to obtain an accurate description of the solutions on finite regions of arbitrary size. The time discretisation is based on a semi‐implicit, semi‐Lagrangian approach that handles the highly inhomogeneous node distribution without loss of efficiency. The method is first validated on standard test cases and then applied to the implementation of absorbing open boundary conditions by coupling the semi‐infinite domain to a finite size domain on which the same equations are discretised by standard finite volume methods. Numerical experiments show that the proposed approach does not produce significant spurious reflections at the interface between the finite and infinite domain, thus providing a reliable tool for absorbing boundary conditions. Copyright © 2013 John Wiley & Sons, Ltd.

A Constructive Capacity Lower Bound of the Inhomogeneous Wireless Networks

Many research results in the direction of wireless network capacity are based on the homogeneous Poisson node process and random homogeneous traffic. However, most of the realistic wireless networks are inhomogeneous. And for this kind of networks, this paper gives a constructive capacity lower bound, which may be effective on network designing. To ensure significant inhomogeneities, we select both inhomogeneous node process and traffic. We divide the transmission into two parts: intra-cluster transmission and inter-cluster transmission. Within each distinct cluster, a circular percolation model is proposed and the highway system is established. Different with regular rectangle percolation model, the highway in our model is in the radial direction or around the circle. Based on this model, we propose a routing strategy and get the intra-cluster per-node rate. In the following, among these clusters, we set many "information pipes" connecting them. By getting the results of per-node transmission rate of each part, we can find that the bottleneck of the throughput capacity is caused by the difference of the node density all over the network region. Specially, the lower bound interval of the capacity can be easily obtained when the traffic is inhomogeneous.

Capacity Scaling of Wireless Networks With Inhomogeneous Node Density: Lower Bounds

We consider static ad hoc wireless networks comprising significant inhomogeneities in the node spatial distribution over the area and analyze the scaling laws of their transport capacity as the number of nodes increases. In particular, we consider nodes placed according to a shot-noise Cox process (SNCP), which allows to model the clustering behavior usually recognized in large-scale systems. For this class of networks, we propose novel scheduling and routing schemes that approach previously computed upper bounds to the per-flow throughput as the number of nodes tends to infinity.

Capacity Scaling in Ad Hoc Networks With Heterogeneous Mobile Nodes: The Super-Critical Regime

We analyze the capacity scaling laws of mobile ad hoc networks comprising heterogeneous nodes and spatial inhomogeneities. Most of previous work relies on the assumption that nodes are identical and uniformly visit the entire network space. Experimental data, however, show that the mobility pattern of individual nodes is usually restricted over the area, while the overall node density is often largely inhomogeneous due to the presence of node concentration points. In this paper we introduce a general class of mobile networks which incorporates both restricted mobility and inhomogeneous node density, and describe a methodology to compute the asymptotic throughput achievable in these networks by the store-carry-forward communication paradigm. We show how the analysis can be mapped, under mild assumptions, into a Maximum Concurrent Flow (MCF) problem over an associated Generalized Random Geometric Graph (GRGG). Moreover, we propose an asymptotically optimal scheduling and routing scheme that achieves the maximum network capacity.

Capacity scaling of wireless networks with inhomogeneous node density: upper bounds

We analyze the capacity scaling laws of wireless ad hoc networks comprising significant inhomogeneities in the node spatial distribution over the network area. In particular, we consider nodes placed according to a shot-noise Cox process, which allows to model the clustering behavior usually recognized in large-scale systems. For this class of networks, we introduce novel techniques to compute upper bounds to the available per-flow throughput as the number of nodes tends to infinity, which are tight in the case of interference limited systems.

Sonographische Diagnostik regionärer Halslymphknotenmetastasen bei Patienten mit Kopf-Hals-Malignomen: Sonomorphologische Kriterien und diagnostische Treffsicherheit*

High resolution sonography is generally considered a diagnostic tool with high sensitivity but low specificity in the assessment of cervical lymph node metastases. This study shows, that excellent sonographic results regarding sensitivity and specificity can be achieved, if sonomorphologic parameters, such as size, shape, delineation and type of echo pattern are included in the evaluation. We compared sonomorphology and histology of 82 patients operated for head and neck malignancies. The sonomorphological and histological findings in the largest lymph nodes in all neck areas were compared, and if a definite identification was possible, also in the second largest ones. Virtually, all longitudinal nodes of any size and practically all oval nodes of an axial diameter of up to 20 mm were found to be free of metastases, whereas 80% of round nodes with an axial diameter of up to 20 mm and practically all round and oval nodes exceeding 20 mm in axial diameter as well as irregularly shaped, poorly delineated and structurally inhomogeneous nodes demonstrated metastatic disease. On the basis of these results we have established the following criteria for the assessment of cervical lymph node metastases: All findings demonstrating longitudinal nodes of any size and oval nodes less than 20 mm in axial diameter are to be considered sonographically negative, whereas findings in which oval nodes exceeding 20 mm in axial diameter, as well as round, irregularly shaped, poorly delineated or inhomogeneous lymph nodes are found to be classified malignant. Of 58 sonographically positive neck areas, 54 were found to be malignant on histological examination, while 23 of 24 sonographically negative areas corresponded with histologically benign findings.(ABSTRACT TRUNCATED AT 250 WORDS)