• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.4 no.6
• /
• pp.1133-1151
• /
• 2010

Energy balanced consumption routing is based on assumption that the nodes consume energy both in transmitting and receiving. Lopsided energy consumption is an intrinsic problem in low-cost sensor networks characterized by multihop routing and in many traffic overhead pattern networks, and this irregular energy dissipation can significantly reduce network lifetime. In this paper, we study the problem of maximizing network lifetime through balancing energy consumption for uniformly deployed low-cost sensor networks. We formulate the energy consumption balancing problem as an optimal balancing data transmitting problem by combining the ideas of corona cluster based network division and optimized transmitting state routing strategy together with data transmission. We propose a localized cluster based routing scheme that guarantees balanced energy consumption among clusters within each corona. We develop a new energy cluster based routing protocol called "OECR". We design an offline centralized algorithm with time complexity O (log n) (n is the number of clusters) to solve the transmitting data distribution problem aimed at energy balancing consumption among nodes in different cluster. An approach for computing the optimal number of clusters to maximize the network lifetime is also presented. Based on the mathematical model, an optimized energy cluster routing (OECR) is designed and the solution for extending OEDR to low-cost sensor networks is also presented. Simulation results demonstrate that the proposed routing scheme significantly outperforms conventional energy routing schemes in terms of network lifetime.

• Journal of Digital Convergence
• /
• v.14 no.9
• /
• pp.309-315
• /
• 2016

The node mobility in the wireless mobile network environment increases the energy consumption. This paper proposes a CNMA (cluster-based node management algorithm) to reduce the energy consumption caused by node mobility, and to prolong the life cycle for cluster member nodes. The proposed CNMA traces the mobility for nodes between cluster header and member, and it analyses the energy capacity as monitoring periodically their relationship. So, it makes a division and merges by analysing the state transition for nodes. This paper is to reduce the energy consumption due to the node mobility. The simulation results show that the proposed CNMA can efficiently control the energy consumption caused by mobility, and it can improve the energy cycle.

• ETRI Journal
• /
• v.31 no.2
• /
• pp.173-181
• /
• 2009

The growth of the World Wide Web and web-based applications is creating demand for high performance web servers to offer better throughput and shorter user-perceived latency. This demand leads to widely used cluster-based web servers in the Internet infrastructure. Load balancing algorithms play an important role in boosting the performance of cluster web servers. Previous load balancing algorithms suffer a significant performance drop under dynamic and database-driven workloads. We propose an estimation-based load balancing algorithm with admission control for cluster-based web servers. Because it is difficult to accurately determine the load of web servers, we propose an approximate policy. The algorithm classifies requests based on their service times and tracks the number of outstanding requests from each class in each web server node to dynamically estimate each web server load state. The available capacity of each web server is then computed and used for the load balancing and admission control decisions. The implementation results confirm that the proposed scheme improves both the mean response time and the throughput of clusters compared to rival load balancing algorithms and prevents clusters being overloaded even when request rates are beyond the cluster capacity.

• The Bulletin of The Korean Astronomical Society
• /
• v.46 no.2
• /
• pp.81.1-81.1
• /
• 2021

Stellar kinematics is a useful tool to understand the formation and evolution of young stellar systems. Here, we present a kinematic study of the HII region, NGC 821, using the Gaia Early Data Release 3. NGC 281 contains the open cluster IC 1590. This cluster has a core and a low-stellar density halo. We detect a pattern of cluster expansion from the Gaia proper motion vectors. Most stars radially escaping from the cluster are distributed in the halo. We measure the 1-dimensional velocity dispersion of stars in the core. The velocity dispersion (1 km/s) is comparable to the expected virial velocity dispersion of this cluster, and therefore the core is at a virial state. The core has an initial mass function shallower than that of the halo, which is indicative of mass segregation. However, there is no significant correlation between stellar masses and tangential velocities. This result suggests that the mass segregation has a primordial origin. On the other hand, it has been believed that the formation of young stars in NGC 281 West was triggered by feedback from massive stars in IC 1590. We investigate the ages of stars in the two regions, but the age difference between the two regions is not comparable to the timescale of the passage of an ionization front. Also, the proper motion vectors of the NGC 281 West stars relative to IC 1590 do not show any systematic receding motion from the cluster. Our results suggest that stars in NGC 281 West might have been formed spontaneously. In conclusion, the formation of NGC 281 can be understood in the context of hierarchical star formation model.

• The Bulletin of The Korean Astronomical Society
• /
• v.42 no.1
• /
• pp.52.1-52.1
• /
• 2017

Galaxy clusters are the most massive gravitationally bound systems and thus probably the most recent objects to form. One of promising routes to understand the assembly history of galaxy clusters is to measure observable quantities of components in clusters that are sensitive to the evolutionary state of the cluster. Recent deep observations on the nearby clusters show distinct diffuse intracluster light (ICL), that the light from stars are not bound any individual cluster galaxy, however until now this component has not been well studied due to its faint nature, with typical brightness of ~100 times fainter than the sky background. As shown in galaxy cluster simulation studies, the ICL abundance increases during various dynamical exchanges of galaxies such as the disruption of dwarf galaxies, major mergers between galaxies and the tidal stripping of galaxies. Thus, the ICL is an effective tool to measure the evolutionary stage of galaxy clusters. Moreover, the investigation of the ICL evolution mechanism will allow us understand the galaxy evolution process therein. In this pilot study, we target the Coma cluster, where the existing ICL studies are limited only in the central region. With large and uniform deep optical images from the Subaru telescope, available only recently (Okabe et al. 2014), we are developing a robust ICL measurement technique, extracting the ICL surface brightness and color profiles, which will allow us to study the origin of the ICL and its connection to the evolutionary history of the Coma cluster. For the next phase, we plan to utilize the plenty of spectroscopy data from the MMT telescope to compare ICL properties with the star formation history of the brightest cluster galaxies (BCG), and discuss the ICL formation mechanism of the Coma cluster by comparing the distribution of cluster galaxies with the distribution of diffuse light inside the Coma cluster.

• Journal of the Korean association of regional geographers
• /
• v.22 no.2
• /
• pp.397-410
• /
• 2016

Although industrial complexes have played as an engine of the Korean economy for the last 40 years, the majority of industrial complexes shows limitations to the continuous growth such as a lack of innovation capabilities and social capital, conceived as a key to transforming into clusters of innovation. To overcome those problems, the Korean government embarked on the cluster policy from the mid 2000's, focusing on promoting the endogenous development capabilities of individual industrial complexes. Drawing upon the in-depth case study of the Gumi IT cluster, one of the representative large-scale industrial complexes in Korea, the authors conclude that the cluster policy has contributed to making the Gumi IT cluster enhance the capabilities of endogenous development through the facilitation of self-organizing learning communities within the cluster.

• International Journal of Internet, Broadcasting and Communication
• /
• v.13 no.3
• /
• pp.178-192
• /
• 2021

File system forensics typically focus on the contents or timestamps of a file, and it is common to work around file/directory centers. But to recover a deleted file on the disk or use a carving technique to find and connect partial missing content, the evidence must be analyzed using cluster-centered analysis. Forensics tools such as EnCase, TSK, and X-ways, provide a basic ability to get information about disk clusters, but these are not the core functions of the tools. Alternatively, Sysinternals' DiskView tool provides a more intuitive visualization function, which makes it easier to obtain information around disk clusters. In addition, most current tools are for Windows. There are very few forensic analysis tools for MacOS, and furthermore, cluster analysis tools are very rare. In this paper, we developed a tool named FACT (Forensic Analyzer based Cluster Information Tool) for analyzing the state of clusters in a HFS+ file system, for digital forensics. The FACT consists of three features, a Cluster based analysis, B-tree based analysis, and Directory based analysis. The Cluster based analysis is the main feature, and was basically developed for cluster analysis. The FACT tool's cluster visualization feature plays a central role. The FACT tool was programmed in two programming languages, C/C++ and Python. The core part for analyzing the HFS+ filesystem was programmed in C/C++ and the visualization part is implemented using the Python Tkinter library. The features in this study will evolve into key forensics tools for use in MacOS, and by providing additional GUI capabilities can be very important for cluster-centric forensics analysis.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.8 no.2
• /
• pp.664-677
• /
• 2014

Wind energy has proven its viability by the emergence of countless wind turbines around the world which greatly contribute to the increased electrical generating capacity of wind farm operators. These infrastructures are usually deployed in not easily accessible areas; therefore, maintenance routines should be based on a well-guided decision so as to minimize cost. To aid operators prior to the maintenance process, a condition monitoring system should be able to accurately reflect the actual state of the wind turbine and its major components in order to execute specific preventive measures using as little resources as possible. In this paper, we propose a fault detection approach which combines cluster analysis and frequent pattern mining to accurately reflect the deteriorating condition of a wind turbine and to indicate the components that need attention. Using SCADA data, we extracted operational status patterns and developed a rule repository for monitoring wind turbine systems. Results show that the proposed scheme is able to detect the deteriorating condition of a wind turbine as well as to explicitly identify faulty components.

• International Journal of Precision Engineering and Manufacturing
• /
• v.9 no.3
• /
• pp.59-63
• /
• 2008

A static load analysis of twin-screw kneaders is required not only for the dynamic analysis, but also because it is the basis of the stiffness and strength calculations that are essential for the design of bearings. In this paper, the static loads of twin-screw kneaders are analyzed, and a mathematical model of the force and torque moments is presented using a numerical integration method based on differential geometry theory. The calculations of the force and torque moments of the twin-screw kneader are given. The results show that the $M_x$ and $M_y$ components of the fluid resistance torque of the rotors change periodically in each rotation cycle, but the $M_z$ component remains constant. The axis forces $F_z$ in the female and male rotors are also constant. The static load calculated by the proposed method tends to be conservative compared to traditional methods. The proposed method not only meets the static load analysis requirements for twin-screw kneaders, but can also be used as a static load analysis method for screw pumps and screw compressors.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
• /
• 1997.11a
• /
• pp.104-111
• /
• 1997

Cluster systems are microcrystals of vanadiumoxided compounds such as Barium, Calcium or Sodium Metavanadates or Sodium Vanadium Bronze which are distributed into dimethyl- or diethylphosphites or microcrystals of vanadium oxides, for instance, vanadium oxide (+3), distributed into the methylphosphonic acid melted. During the interaction of vanadium compounds with the correspondent phosphororganic substances biue viscous liquids are formed. These liquids have paramagnetic properties. According to the UV and IR spectroscopic investigations as well as the results of EPR spectra the substances obtained consist of the nucleus containing 6 to 12 of vanadium atoms and the shell including ligands which are molecules of phosphites or methylphosphonic acid. Here every atom of vanadium interacts with four of phosphorus containing molecules. Sizes of the particles in these systems donot exceed 200 nm. Introduction of cluster systems (0,1 -0,3 % vanadium) into epoxy compositions before the introduction of curing agent - polyethylenepolyamine 6 -8 % leads to the acceleration of composition crosslinking and to the combustion decreasing: 1) Oxygen Index grows to 35: 2)mass losses during combustion decrease to 1-2%, 3) combustion time does not exceed 1 s; 4) the intumescence of material sample is being observed during the burner action as well as the foam coke formation.