Passive Clustering Research Articles

The Grism Lens-amplified Survey from Space (Glass). IX. The Dual Origin of Low-mass Cluster Galaxies as Revealed by New Structural Analyses

Abstract Using deep Hubble Frontier Fields imaging and slitless spectroscopy from the Grism Survey from Space, we study 2200 cluster and 1748 field galaxies at to determine the impact of environment on galaxy size and structure at stellar masses , an unprecedented limit at these redshifts. Based on simple assumptions— —we find no significant differences in half-light radii (r e ) between equal-mass cluster or field systems. More complex analyses— —reveal local density (Σ) to induce only a 7% ± 3% (95% confidence) reduction in r e beyond what can be accounted for by U − V color, Sérsic index (n), and redshift (z) effects. Almost any size difference between galaxies in high- and low-density regions is thus attributable to their different distributions in properties other than environment. Indeed, we find a clear color–r e correlation in low-mass passive cluster galaxies ( ) such that bluer systems have larger radii, with the bluest having sizes consistent with equal-mass star-forming galaxies. We take this as evidence that large-r e low-mass passive cluster galaxies are recently acquired systems that have been environmentally quenched without significant structural transformation (e.g., by ram pressure stripping or starvation). Conversely, ∼20% of small-r e low-mass passive cluster galaxies appear to have been in place since . Given the consistency of the small-r e galaxies’ stellar surface densities (and even colors) with those of systems more than ten times as massive, our findings suggest that clusters mark places where galaxy evolution is accelerated for an ancient base population spanning most masses, with late-time additions quenched by environment-specific mechanisms mainly restricted to the lowest masses.

Cis and Trans Cooperativity of E-Cadherin Mediates Adhesion in Biomimetic Lipid Droplets

The regulation of cell-cell adhesion is important in cell motility, tissue growth, and for the mechanical integrity of tissues. Although the role of active cytoskeleton dynamics in regulating cadherin interactions is crucial in vivo, here we present a biomimetic emulsion system to characterize the passive E-cadherin-mediated adhesion between droplets. The visualization of a three-dimensional assembly of lipid droplets, functionalized with extracellular E-cadherin domains, reveals a hierarchy of homophilic interactions. First, the high interfacial tension of droplets facilitates trans cadherin-cadherin adhesion, which is strong enough to stabilize looser than random close packing configurations. Second, fluorescence enhancement shows that adding clustering agents, such as calcium or chelating ligands, favor the lateral cis adhesion of the already bound cadherin pairs over the clustering of monomer cadherin on the surface. Finally, above a threshold cadherin and calcium concentration, the cis and trans protein interactions become strong enough to trigger and promote droplet fusion. While E-cadherin is not known to participate in cellular fusion, this mechanism is general because replacing calcium with cholesterol to cluster the cadherin-carrying lipids also promotes fusion. These results suggest that passive clustering, via calcium-induced dimerization or membrane ordering, may contribute to the reinforcement of cell-cell contacts. Alternatively, a molecular switch for fusion offers a route to mixing droplet contents and controlling their size in situ.

Location Aware Data Aggregation for Efficient Message Dissemination in Vehicular Ad Hoc Networks

An intelligent location-aware data aggregation mechanism for real-time observation, estimation, and efficient dissemination of any kind of traffic information in vehicular ad hoc networks (VANETs) is presented in this paper. The mechanism introduces a location awareness algorithm, enabling spatiotemporal database indexing and providing the location context of the messages without the use of advanced positioning systems such as satellite navigation and digital maps. Intelligent passive clustering and adaptive broadcasting are used to minimize the number of messages exchanged, packet collisions, and network load. The incoming messages are fused by a Kalman filter, allowing the description of the traffic-related information as a system characterized by as many variables as needed, depending on the application design. The scheme allows the comparison of aggregates and single observations, which enables their merging and better overall accuracy. Old information in aggregates is removed by real-time database refreshing, thus leaving only newer relevant information for the driver to make real-time decisions in traffic. The mechanism is generic and can be used for any kind of VANET information. It is evaluated by extensive simulations to show the efficiency and accuracy.

Energy conservation in WSN through multilevel data reduction scheme

Lifetime is one of the major Quality of Service factors for Wireless Sensor Networks (WSN). As sensor nodes are generally battery-powered devices, the network lifetime can be extended over a reasonable time span by lessening the energy consumption of nodes. Reducing the amount of data transmission can effectively minimize the energy consumption, the bandwidth requirement and network congestions. In a WSN, denser deployment of nodes results in a high spatial correlation between data generated by neighboring nodes. Slow varying nature of many physical phenomenon results in similar sensor observations over the period. In this proposed work, a two level data reduction technique is employed. Here the Data and Energy Aware Passive (DEAP) clustering approach is introduced to divide the sensor network into data similar clusters. A Dual Prediction (DP) based reporting is deployed between cluster members and their Cluster Head (CH). This first level data reduction is attributed to the temporal correlation of data over the time. In CHs, the data from multiple data similar nodes are aggregated to reduce the spatial data redundancy. The proposed method DEAP-DP is verified with real world datum and has achieved up to 68% data reduction at 0.5°C error tolerance.

YouLighter: A Cognitive Approach to Unveil YouTube CDN and Changes

YouTube relies on a massively distributed content delivery network (CDN) to stream the billions of videos in its catalog. Unfortunately, very little information about the design of such CDN is available. This, combined with the pervasiveness of YouTube, poses a big challenge for Internet service providers (ISPs), which are compelled to optimize end-users’ quality of experience (QoE) while having almost no visibility and understanding of CDN decisions. This paper presents YouLighter , an unsupervised technique that builds upon cognitive methodologies to identify changes in how the YouTube CDN serves traffic. YouLighter leverages only passive measurements and clustering algorithms to group caches that appear colocated and identical into edge-nodes. This automatically unveils the YouTube edge-nodes used by the ISP customers. Next, we leverage a new metric, called Pattern Dissimilarity , that compares the clustering results obtained from two different time snapshots to pinpoint sudden changes. By running YouLighter over 10-month long traces obtained from two ISPs in different countries, we pinpoint both sudden changes in edge-node allocation, and small alterations to the cache allocation policies, which actually impair the QoE that the end-users perceive.

우리나라 성인의 건강행태군집 유형과 관련요인

Abstract This study sought to identify types of health behavior clusters among Korean adults and their related factors. A secondary analysis of 1,441 subjects, aged 19 to 64, in the 2009 Korean National Health and Nutrition Examination Survey (KNHANES IV-3) was conducted. A cluster analysis was used to identify types of clusters related to physical activity, smoking, and alcohol drinking. A complex samples chi square test and multivariate logistic regression were performed to analyze the associations between types of health behavior clusters and sample’s characteristics using SPSS WIN 21. Five clusters were identified: health promotion, smoking, alcohol drinking, passive attitude, and risky behavior. The passive attitude cluster had the most subjects, with 47.7% of subjects as members. Socio-demographic factors, hypertension, and depressive symptoms were associated with membership in the alcohol drinking, smoking, passive attitude, or risky behavior cluster rather than the health promotion cluster. The findings of this study suggest that integrated health promotion programs incorporating multiple strategies need to be investigated. In addition, further studies should explore psychosocial factors that affect health behavior clusters, such as stress, self-efficacy, social support, and social networks.

Link Aware Data Aggregation Mechanism based on Passive Clustering in Wireless Sensor Network

In Wireless Sensor Network (WSN) each node must report to the Base Station (BS) with the frequency that the BS demands (Nre). The paper proposes Enhanced Link aware Data Aggregation Mechanism (LDAM), an energy efficient data gathering algorithm that elects the Cluster Head (CH) and Gateway (GW) nodes based on the Predicted Transmission Count (PTC) that depends on the residual energy, forward and reverse delivery ratio. Once the clusters are formed, nodes calculate their distance(d) from CH based on which the nodes take-in varied transmission power. Based on the nodes weight, CH and GW are re-elected periodically and this enhances the nodes lifetime. Algorithm is simulated with varied number of nodes in the network, results prove to be efficient than LCM algorithm with respect to delivery ratio, energy consumed and average delay.

Research on Large-scale Adhoc Routing Protocols

Based on Passive Clustering protocol in this paper, a new type of suitable for large-scale wireless sensor network routing protocol, called RBPC protocol, which USES the Passive Clustering routing Reply Broadcast routing protocol, the purpose is to make full use of the routing Reply (the Route Reply, RREP) group, the RREP Reply when routing requests in Broadcast way, a lot of CH nodes by receiving the grouping and routing are cached in the local, thereby reducing the Route setup times throughout the network, and reduces the source node due to establish routing packet delay.

Why some electricity utilities actively promote energy efficiency while others do not—a Swiss case study

Electricity utilities are key players for promoting energy efficiency (EE) because of their close link to consumers. Utility-centered EE policy frameworks, such as white certificate schemes coupled to saving obligations, have been shown to be both effective and efficient in several US states and various European countries. In Switzerland, where such a policy framework is absent on a national level, large differences occur among utility providers in their activities to promote EE. This study sheds light on this issue, using data from a survey of Swiss utilities (N = 114). A two-step cluster analysis was used to identify three groups of utilities. It is based on these utilities’ evaluation of 20 incentives and constraints for promoting EE. An analysis of variance found significant differences between the clusters regarding size (number of employees), share of production, number of large clients, and—most importantly—level of activity in implementing EE programs. The most active cluster comprises mainly larger utility companies, which primarily see the incentives of promoting EE. The passive cluster consists of small companies, focusing primarily on constraints. There is also an ambivalent cluster. It includes middle-sized companies, which see both clear incentives and many constraints – mainly a lack of human and capital resources—for engaging in EE. Based on our analysis, we conclude that due to the large heterogeneity of Swiss utilities, there is a need for contextualized policies targeting different types of utilities in order to effectively promote EE.

A kind of energy-efficiency wireless sensor network model based on passive clustering algorithm

This paper presents an energy-efficiency wireless sensor network (WSN) model; the model based on passive clustering strategy creates its clustering network topology only when there are data communication requests in WSN, and the creation and the maintenance of the topology are both local to complete, and need no extra control commands to save energy. In this clustering strategy, the selection of cluster head takes a mechanism named 'first declarant enunciator wins'. The election of gateway node is decided according to the rules that make trade-offs between the network robust and energy-efficient. The creation and maintenance process of the cluster network are described in detail in this paper. The simulation result is also presented in NS2, which shows that directed diffusion routing that adopts the model is more energy-efficient than those that do not adopt it, and has a good performance even when the nodes number increases in large scale.

Passive Distributed Clustering Scheme in Wireless Sensor Networks

Energy efficiency is especially important for the cluster of the wireless sensor network (WSN). This paper studies how to increase availability and survivability of WSN by selecting a suitable cluster head. For this purpose, we propose a passive distributed clustering scheme (PDCS), to promote the efficiency of energy utilization. In PDCS, both the relative distance and the residual energy are taken into consideration for cluster head selection. Simulation results present that PDCS has better performance than the well-known LEACH scheme.

ADVANCED ENERGY EFFICIENT PASSIVE CLUSTERING MOBILITY IN WIRELESS SENSOR NETWORKS

Wireless sensor networks have a wide applicability and increase deployment in the near future. In most of those applications, the network is composed of an i mportant number of nodes deployed in an extensive area in which not all nodes are directly connected and b ased on clustering techniques. The Clustering can considerably reduce transmission overhead during fl ooding. In fact, by using clustering, we minimize t he set of forwarding nodes during transmission and con sequently reduce the energy cost and traffic overhead in topology environments. In this study, w e present passive clustering mechanisms and the main clustering protocols proposed for wireless sen sor networks; we also introduce a new protocol designated for mobile nodes in wireless sensor netw ork that is based on the APC-T. This mechanism provides the stability of clusters after each depar ts of cluster-head and allows balanced energy consumption among the sensor nodes. Comparison with the existing schemes such as APC-T and Geographically Repulsive Insomnious Distributed Sensors (GRIDS) proves that the mechanism for selecting a backup of cluster-head nodes, which is the most important factor influencing the clusterin g performance, can significantly improves the network lifetime.

CLASH-VLT: The mass, velocity-anisotropy, and pseudo-phase-space density profiles of thez= 0.44 galaxy cluster MACS J1206.2-0847

We use an unprecedented data-set of about 600 redshifts for cluster members, obtained as part of a VLT/VIMOS large programme, to constrain the mass profile of the z=0.44 cluster MACS J1206.2-0847 over the radial range 0-5 Mpc (0-2.5 virial radii) using the MAMPOSSt and Caustic methods. We then add external constraints from our previous gravitational lensing analysis. We invert the Jeans equation to obtain the velocity-anisotropy profiles of cluster members. With the mass-density and velocity-anisotropy profiles we then obtain the first determination of a cluster pseudo-phase-space density profile. The kinematics and lensing determinations of the cluster mass profile are in excellent agreement. This is very well fitted by a NFW model with mass M200=(1.4 +- 0.2) 10^15 Msun and concentration c200=6 +- 1, only slightly higher than theoretical expectations. Other mass profile models also provide acceptable fits to our data, of (slightly) lower (Burkert, Hernquist, and Softened Isothermal Sphere) or comparable (Einasto) quality than NFW. The velocity anisotropy profiles of the passive and star-forming cluster members are similar, close to isotropic near the center and increasingly radial outside. Passive cluster members follow extremely well the theoretical expectations for the pseudo-phase-space density profile and the relation between the slope of the mass-density profile and the velocity anisotropy. Star-forming cluster members show marginal deviations from theoretical expectations. This is the most accurate determination of a cluster mass profile out to a radius of 5 Mpc, and the only determination of the velocity-anisotropy and pseudo-phase-space density profiles of both passive and star-forming galaxies for an individual cluster [abridged]

Passive cluster-based multipath routing protocol for wireless sensor networks

Energy efficiency and quality of service (QoS) are both essential issues in the applications of wireless sensor networks (WSNs) all along, which are mainly reflected in the development of routing and MAC protocols. However, there is little design for achieving the dual performances simultaneously. In this paper, we develop a practical passive cluster-based node-disjoint many to one multipath routing protocol to satisfy the requirements of energy efficiency and QoS in practical WSNs. Passive clustering approach is put to use in the first round, while active clustering technique is taken in the other rounds. Implementation of smart delay strategy makes the cluster distribute uniformly, as well as lessen the number of nodes that have taken part in routing. Among cluster heads, a node-disjoint many to one multipath routing discovery algorithm, which is composed of the optimal path searching process and multipath expansion process, is implemented to find multiple paths at the minimum cost. The simulation results show the proposed protocol achieved very good performance both in energy efficiency and QoS.

Passive Clustering for Efficient Energy Conservation in Wireless Sensor Network

A wireless sensor network is a set of miniature nodes that consume little energy and route information to a base station. It will enable reliable monitoring of a wide variety of phenomena for civilian, military and medical applications. Almost any sensor network application requires some form of self-organisation to route information. Recent years many protocols for network self-organization and management have been proposed and being implemented. Hierarchical clustering algorithms are very important in increasing the network’s life time. The most important point in this algorithm is cluster head selection and cluster formation because a good clustering guarantees reliability, energy efficiency and load balancing in the network. In this paper, we will use the principles of passive clustering to propose a new mechanism for selecting clusterheads. This mechanism allows the election of an alternate for each cluster head and a dynamic balancing of the role of clusterhead to the alternate when leaving or failure. Thus, it provides several advantages network reliability, stability of clusters and reduces energy consumption among the sensor nodes. Comparison with the existing schemes such as Passive Clustering and GRIDS (Geographically Repulsive Insomnious Distributed Sensors) reveals that the mechanism for selecting an alternate for clusterhead nodes, which is the most important factor influencing the clustering performance, can significantly improves the network lifetime.

Scalable Cluster-based Routing in Large Wireless Sensor Networks

Large control overhead is the leading factor limiting the scalability of wireless sensor networks (WSNs). Clustering network nodes is an efficient solution, and Passive Clustering (PC) is one of the most efficient clustering methods. In this letter, we propose an improved PC-based route building scheme, named Route Reply (RREP) Broadcast with Passive Clustering (in short RBPC). Through broadcasting RREP packets on an expanding ring to build route, sensor nodes cache their route to the sink node, which reduces the total route search times and thus the control overhead. Simulation results are also provided to show the efficiency of the proposed RBPC in terms of reduced overhead and energy consumption, and it is also shown that RBPC outperforms AODV/PC in the delivery ratio.

Abundance of CuZn + SnZn and 2CuZn + SnZn defect clusters in kesterite solar cells

Kesterite solar cells show the highest efficiency when the absorber layers (Cu2ZnSnS4 [CZTS], Cu2ZnSnSe4 [CZTSe] and their alloys) are non-stoichiometric with Cu/(Zn+Sn)≈0.8 and Zn/Sn≈1.2. The fundamental cause is so far not understood. Using a first-principles theory, we show that passivated defect clusters such as CuZn+SnZn and 2CuZn+SnZn have high concentrations even in stoichiometric samples with Cu/(Zn+Sn) and Zn/Sn ratios near 1. The partially passivated CuZn+SnZn cluster produces a deep donor level in the band gap of CZTS, and the fully passivated 2CuZn+SnZn cluster causes a significant band gap decrease. Both effects are detrimental to photovoltaic performance, so Zn-rich and Cu, Sn-poor conditions are required to prevent their formation and increase the efficiency. The donor level is relatively shallower in CZTSe than in CZTS, which gives an explanation to the higher efficiency obtained in Cu2ZnSn(S,Se)4 (CZTSSe) cells with high Se content.

The role of stellar mass and environment for cluster blue fraction, AGN fraction and star formation indicators from a targeted analysis of Abell 1691

We present an analysis of the galaxy population of the intermediate X-ray luminosity galaxy cluster, Abell 1691, from SDSS and Galaxy Zoo data to elucidate the relationships between environment and galaxy stellar mass for a variety of observationally important cluster populations that include the Butcher-Oemler blue fraction, the active galactic nucleus (AGN) fraction and other spectroscopic classifications of galaxies. From 342 cluster members, we determine a cluster recession velocity of 21257+/-54 km/s and velocity dispersion of 1009^+40_-36 km/s and show that although the cluster is fed by multiple filaments of galaxies it does not possess significant sub-structure in its core. We identify the AGN population of the cluster from a BPT diagram and show that there is a mild increase in the AGN fraction with radius from the cluster centre that appears mainly driven by high mass galaxies (log(stellar mass)>10.8). Although the cluster blue fraction follows the same radial trend, it is caused primarily by lower mass galaxies (log(stellar mass)<10.8). Significantly, the galaxies that have undergone recent star-bursts or are presently star-bursting but dust-shrouded (spectroscopic e(a) class galaxies) are also nearly exclusively driven by low mass galaxies. We therefore suggest that the Butcher-Oemler effect may be a mass-dependant effect. We also examine red and passive spiral galaxies and show that the majority are massive galaxies, much like the rest of the red and spectroscopically passive cluster population. We further demonstrate that the velocity dispersion profiles of low and high mass cluster galaxies are different. Taken together, we infer that the duty cycle of high and low mass cluster galaxies are markedly different, with a significant departure in star formation and specific star formation rates observed beyond r_200 and we discuss these findings.

PassCAR: A passive clustering aided routing protocol for vehicular ad hoc networks

Vehicular ad hoc networks (VANETs) are a promising architecture for vehicle-to-vehicle communications in the transportation field. However, the frequent topology changes in VANETs create many challenges to data delivery because the vehicle velocity varies with time. Thus, designing an efficient routing protocol for stable and reliable communication is essential. Existing studies show that clustering is an elegant approach to efficient routing in a mobile environment. In particular, the passive clustering (PC) mechanism has been validated as a more efficient approach compared to traditional clustering mechanisms. However, the PC mechanism was primarily designed for mobile ad hoc networks (MANETs), and may be unsuitable for constructing a cluster structure in VANETs because it does not account for vehicle behavior and link quality. In this paper, we propose a passive clustering aided routing protocol, named PassCAR, to enhance routing performance in the one-way multi-lane highway scenario. The main goal of PassCAR is to determine suitable participants for constructing a stable and reliable cluster structure during the route discovery phase. Each candidate node self-determines its own priority to compete for a participant using the proposed multi-metric election strategy based on metrics such as node degree, expected transmission count, and link lifetime. Simulation results show that, compared with the original PC mechanism, PassCAR not only increases the successful probability of route discovery, but also selects more suitable nodes to participate in the created cluster structure. This well-constructed cluster structure significantly improves the packet delivery ratio and achieves a higher network throughput due to its preference for reliable, stable, and durable routing paths.

On the use of passive clustering in wireless video sensor networks

Wireless Video Sensor Networks are foreseen to be of a paramount importance in realising a wide spectrum of applications, mainly surveillance, target tracking and environment monitoring. In this paper, we propose a combination of an improved clustering algorithm and Directed Diffusion (DD), a well–known data–centric routing paradigm in sensor networks. On one hand, clustering allows to save bandwidth required by rich and intensive data of video applications. On the other hand, the network lifetime is prolonged by implementing an energy–aware load–balancing feature through modifying Passive Clustering (PC) rules for building/maintaining its topology. We performed extensive computer simulations and show in this paper that our solution outperforms original DD as well as when it is combined with PC with energy considerations but without load balancing.