• Proceedings of the Korea Information Processing Society Conference
• /
• 2016.04a
• /
• pp.124-126
• /
• 2016

Successful deployment of the Software Defined Network (SDN) depends on its ability to cope up with network failures. There are various types of failures that may occur in an SDN. The most common are switch and link failures. It is necessary to recover the network from failures for a continuous service availability. But for the real-time services fast recovery from the failure is required to minimize the service disruption time. In the proposed work, we focused on minimizing the recovery time after the failure is detected. Once the failure is detected, the controller involvement is needed to dynamically reroute the failure disrupted flows from the failed component to an alternate path. The aim of the proposed scheme is to provide a traffic management scheme which can react to the dynamic network events by rapidly modifying the forwarding behavior of the switches for faster in-band network adaptability. The proposed scheme (1) Considers the shared data and control path delay (2) Optimally utilize the network resources (3) Eliminates the need of constant monitoring overhead at the controller which results into faster detouring and ultimately rapid recovery.

• Journal of the Society of Naval Architects of Korea
• /
• v.42 no.6 s.144
• /
• pp.608-618
• /
• 2005

A new technique giving significant drag reduction in turbulent shear flows has been proposed by using the buoyancy effect to generate periodic spanwise motion. Such spanwise motion can be obtained by arranging heating and cooling strips periodically aligned in the spanwise direction of a vertical channel, where the streamwise mean flow is perpendicular to the gravity vector The strip size has been changed in order to obtain the optimum size corresponding to the maximum drag reduction. The bulk Reynolds number, $ Re_{m} = U_{m} \delta / \nu \$ is fixed at 2270 while Grashof numbers is changed between $10^{6}$ to $10^{7}$. As Grashof number increases, considerable drag reduction can be obtained, At the highest Grashof number, an optimum strip size of about 250 wail units gives drag reduction of about 35$\%$. The greater the Grashof number, the smaller the strip size attains the maximum drag reduction.

• The KIPS Transactions:PartD
• /
• v.10D no.6
• /
• pp.907-916
• /
• 2003

Database benchmarks require efficient of large-scale data. This presents the system architecture, control flows, and characteristics of the data generator we have developed. The data generator features generation of large-scale data, column-by-column data generation, a number of data distributions and verification, and real data generation. An extensive conparison with other data generators in terms of function is also presented. Finally, empirical performance experiments between RAID systems and non-RAID one have been conducted to alleviate I/O bottleneck. The test results can serve as guidelines to help confifure system architecture.

• Journal of Satellite, Information and Communications
• /
• v.5 no.2
• /
• pp.87-91
• /
• 2010

The IEEE 802.15.4 and IEEE 802.15.7 standard are the typical of low rate wireless and Visible Light Wireless personal area networks. Its Medium Access Control protocol can support the QoS traffic flows for real-time application through guaranteed time slots (GTS) in beacon mode. However, how to achieve a best allocation scheme is not solved clearly. The current analytical models of IEEE 802.15.4 MAC reported in the literature have been mainly developed under the assumption of saturated traffic or non-bursty unsaturated traffic conditions. These assumptions don't capture the characteristics of bursty multimedia traffic. In this paper, we propose a new analytical model for GTS allocation with burst Markov modulated ON-OFF arrival traffic.

• Journal of Distribution Science
• /
• v.11 no.7
• /
• pp.23-30
• /
• 2013

Purpose - The study attempts to investigate the relationship between inventory management and firm performance using a multi-dimensional aspect of inventory management with respect to lean management practices across countries. Research design, data, and methodology - 1643 manufacturing firms from Japan and the US that SIC ranges from 2000 to 3999 were chosen to conduct the empirical test. This study employs hierarchical OLS regression analysis to examine the impact of control variables, ABI, EBI, and the interaction between ABI and EBI on firm performance. Results - The result indicates that in Japan high level of inventory negatively influences the accounting flows of business, while US manufactures exhibit strong positive impact of ELI on firm performance across accounting and market measures. The results show that the complementarity between the amount and the speed of inventory does exist. Except for Tobin's q, the sign of interaction term coefficient is negative, suggesting that when the amount of inventory increases and it stays longer in a firm, market values, ROS, and ROA suffers. Conclusions - The major finding of this study is that there exist some complementarities between the scope and implication of inventory management for lean strategy across countries, particularly in U.S. and Japanese firms.

• 전자공학회논문지 IE
• /
• v.44 no.1
• /
• pp.1-5
• /
• 2007

This experiment was analysed the discharge characteristics of FFL(flat fluorescent lamp). FFL is operated by sine and pulse wave source. We use FFL which has the electrodes covered with dielectric, observed the discharge characteristics of FFL by V-Q Lissajous' figure. When FFL is operated with pulsed, the discharge current flows after the applied voltage is risen. When the duty ratio increases, the number of metastable xenon atoms seem to increase. Consequently, the 172nm radiation becomes strong as the duty ratio increases.

• Journal of Environmental Science International
• /
• v.27 no.2
• /
• pp.99-107
• /
• 2018

In order to design the improvement process for T-N removal, the treatment process of Suyoung, Gangbyeon, and Noxan sewage treatment plants (STP) in Busan was anlayzed. Suyoung STP shows a T-N removal efficiency of about 69.8% with MLE(Modified Ludzack ettinger) and A2O+MBR. However, it is necessary to improve the process to maintain over DO of 1 mg/L and is required to install a flow control tank to minimize the rainfall effect. Gangbyun STP shows a about 70.2% T-N removal efficiency with A2O+GFF(gravity fiber filtration). However, in order to improve T-N removal efficiency, it is needed to install MLE process to treat recycle water. Noksan STP shows a T-N removal efficiency of about 71.0% with MLE+Chemical treatment and shows stable T-N concentration in effluent. However, it is required a toxic chemical management process because bad wastewater flows into the STP, also is necessary a process improvement in order to increase internal recycling ratio. Especially, it is required a process improvement to increase HRT of nitrification tank because Suyoung and Gangbyeon STPs shows low nitrification efficiency during winter season.

• The Bulletin of The Korean Astronomical Society
• /
• v.41 no.1
• /
• pp.45.2-45.2
• /
• 2016

In this study we investigate 195 spacecraft anomalies from 1998 to 2010 from Satellite News Digest (SND). We classify these data according to types of anomaly : Control, Power, Telemetry etc. We examine the association between these anomaly data and daily peak particle (electron and proton) flux data from GOES as well as their occurrence rates. To determine the association, we use two criteria that electron criterion is >10,000 pfu and proton criterion is >100 pfu. Main results from this study are as flows. First, the number of days satisfying the criteria for electron flux has a peak near a week before the anomaly day and decreases from the peak day to the anomaly day, while that for proton flux has a peak near the anomaly day. Second, we found a similar pattern for the mean daily peak particle (electron and proton) flux as a function of day before the anomaly day. Third, an examination of multiple spacecraft anomaly events, which are likely to occur by severe space weather effects, shows that anomalies mostly occur either when electron fluxes are in the declining stage, or when daily proton peak fluxes are strongly enhanced. This result is very consistent with the above statistical studies. Our results will be discussed in view of the origins of spacecraft anomaly.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.20 no.4
• /
• pp.321-329
• /
• 2015

The static synchronous compensator (STATCOM) of cascaded H-bridge configuration accompanying multiple separate DC sides is inherently subject to the problem of uneven DC voltages. These DC voltages in one leg can be controlled by adjusting the AC-side output voltage of each cell inverter, which is proportional to the active power. However, when the phase current is extremely small, large AC-side voltage is required to generate the active power to balance the cell voltages. In this study, an alternative zero-sequence current injection method is proposed, which facilitates effective cell balancing controllers at no load, and has no effect on the power grid because the injected zero sequence current only flows within the STATCOM delta circuit. The performance of the proposed method is verified through simulation and experiments.

• Journal of computational fluids engineering
• /
• v.7 no.1
• /
• pp.10-19
• /
• 2002

The non-staggered(collocated) grid approach in which all the solution variables are located at the centers of control volumes is very popular for incompressible flow analyses because of its numerical efficiency on the curvilinear or unstructured grids. Rhie and Chow's paper is the first in using non-staggered grid method for SIMPLE algorithm, where pressure weighted interpolation was used to prevent decoupling of pressure and velocity. But it has been known that this non-staggered grid method has stability problems when pressure fields are nonlinear like in natural convection flows. Also Rhie-Chow scheme generates large numerical diffusion near curved walls. The cause of these unwanted problems is too large pressure damping term compared to the magnitude of face velocity. In this study the magnitude of pressure damping term of Rhie-Chow's method is limited to 1∼10% of face velocity to prevent physically unreasonable solutions. The wall pressure extrapolation which is necessary for cell-centered FVM is another source of numerical errors. Some methods are applied in a unstructured FV solver and analyzed in view of numerical accuracy. Here, two natural convection problems are solved to check the effect of the Rhie-Chow's method on numerical stability. And numerical diffusion from Rhie-Chow's method is studied by solving the inviscid flow around a circular cylinder.