• Journal of Internet Computing and Services
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• v.5 no.1
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• pp.25-32
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• 2004

Mobile computing environment makes it possible for computing activities to be maintained during movement even if a user changes its network point of attachment. Mobile IP is a standard protocol designed to be used in such mobile computing environment. However, Mobile IP has a drawback to incur a lot of handoff delays and waste network resources, since CoA(Care of Address) registration packets need to go through a HA(Home Agent) first whenever a mobile node moves. To solve this long-standing problem, this paper proposes a new scheme that, for infra-domain movement, efficiently performs local handoff without notifying the HA Specifically, based on the notion of load balance, the proposed scheme allows every FA(Foreign Agent) in a domain to become the root FA(also known as domain FA) dynamically, thus distributing the registration task into many other foreign agents. The dynamic root assignment through load balancing ultimately leads to fast network response due to less frequent transmission of registration packets.

• School Mathematics
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• v.4 no.2
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• pp.161-192
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• 2002

This paper investigated the teaching and teaming of contents-related graphing in Korean secondary textbooks and suggested the improved methods of graph instruction through this analysis. reification-the case of function, In Harel, G., Dubinsky(Eds.), The Concept of Function : Aspects of Epistemology and Pedagogy Textbooks are analyzed from the viewpoint of the proportion of graphing contents, their sequencing, the proportion of each domain in graphing activities (interpretation vs. construction, quantitative vs. qualitative aspect, local vs. global aspect) and tasks (prediction, translation, scaling), and the difference in the graphing contents between the sixth and the seventh curriculum. This analysis demonstrates that graphing contents are increasing in textbooks, therefore the high school textbooks appear in almost every content area. The graphing activities concentrate on the construction, the quantitative aspects, and the local aspects, and are gradually focusing on the interpretation and global aspects of high school textbooks. Furthermore, most of graphing tasks favor translation. In contrast, the current seventh curriculum includes a balance of interpretation and construction activities and has more global aspects than the sixth curriculum based textbooks; however, the qualitative approach still rarely appears. For the graphing tasks, translation is still prevalent, but the importances of prediction tasks based on graph have increased in comparison with the sixth curriculum textbooks. Further, the seventh curriculum based textbooks are designed to stimulate more dynamic graphing instruction by introducing new tools such as graphing calculators and computer software. We suggest that the qualitative and global aspects should be emphasized in early graph instruction, a variety of graph activities in realistic contexts should be performed, and educational technology such as graphing calculator and computer can be efficient to implement these ideas.

• Journal of the Korean Society of Physical Medicine
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• v.10 no.3
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• pp.87-93
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• 2015

PURPOSE: The purpose of this study was to investigate the effects of the 8.5seconds cut-off of the 8-foot up-and-go test as a predictor of falling and a good discriminator of fallers and non-fallers in women in their 60s to 80s. METHODS: The final subjects of this study were 98 elderly women from six senior centers of B metropolitan city. The 8-foot up-and-go test evaluated agility and dynamic balance. The chair-stand test measured the muscle strength for of the lower body. Ankle dorsiflexion and plantar flexion were measured to assess the ankle mobility of the subjects in this study. RESULTS: The below 8.5seconds group showed significantly low values in age and high values in chair-stand (times/30 s), plantar flexion ($^{\circ}$), and K-MMSE (score) compared to the over 8.5seconds group. This group was significantly faster compared to the over 8.5seconds group. In the below 8.5seconds group, only plantar flexion ($^{\circ}$) of all the items showed significantly higher values among those in their 60s compared to those in their 70s and 80s. CONCLUSION: The 8.5seconds cut-off on the 8-foot up-and-go test as a good discriminator and predictor of falling showed differences among fall risk factors (age, lower extremity strength, cognition, and ankle mobility) in women in their 60s to 80s without having regular exercise and a fall experience over the past ones year.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.9
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• pp.4228-4247
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• 2018

Many methods have been developed for the vehicles to create clusters in vehicular ad hoc networks (VANETs). Usually, nodes are vehicles in the VANETs, and they are dynamic in nature. Clusters of vehicles are made for making the communication between the network nodes. Cluster Heads (CHs) are selected in each cluster for managing the whole cluster. This CH maintains the communication in the same cluster and with outside the other cluster. The lifetime of the cluster should be longer for increasing the performance of the network. Meanwhile, lesser the CH's in the network also lead to efficient communication in the VANETs. In this paper, a novel algorithm for clustering which is based on the social behavior of Gray Wolf Optimization (GWO) for VANET named as Intelligent Clustering using Gray Wolf Optimization (ICGWO) is proposed. This clustering based algorithm provides the optimized solution for smooth and robust communication in the VANETs. The key parameters of proposed algorithm are grid size, load balance factor (LBF), the speed of the nodes, directions and transmission range. The ICGWO is compared with the well-known meta-heuristics, Multi-Objective Particle Swarm Optimization (MOPSO) and Comprehensive Learning Particle Swarm Optimization (CLPSO) for clustering in VANETs. Experiments are performed by varying the key parameters of the ICGWO, for measuring the effectiveness of the proposed algorithm. These parameters include grid sizes, transmission ranges, and a number of nodes. The effectiveness of the proposed algorithm is evaluated in terms of optimization of number of cluster with respect to transmission range, grid size and number of nodes. ICGWO selects the 10% of the nodes as CHs where as CLPSO and MOPSO selects the 13% and 14% respectively.

• Journal of the Korean Solar Energy Society
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• v.29 no.2
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• pp.31-38
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• 2009

This study was conducted to forecast inner water temperature strata change by extracting deep water from a dam. For the methodology, the scope wherein the balance between the volume of low-temperature water intake through the virtual water intake opening as installed within the stored water area and the volume of water intake from the surrounding area is not destroyed was calculated through the CFD simulation technique using the computational fluid dynamics(CFD) interpretation method. This study suggested a supplementary method(diffuser) to avoid destroying the water temperature strata, and the effect was reviewed. In case of intake of the same volume, when the velocity of flow of water intake is reduced by increasing the pipe diameter, the destruction of water temperature strata can be minimized. When the area(height) where the intake of water is possible is low, a diffuser for interrupting the vertical direction inflow should be installed to secure favorable water intake conditions in case of water intake on the upper part. This study showed that there was no problem if the intake-enabled, low-temperature area was secured approximately 10m from the bottom when the scope that does not destroy the water temperature strata in case of water intake was forecast using the regression formula.

• Nuclear Engineering and Technology
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• v.48 no.4
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• pp.859-869
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• 2016

Component-scale modeling of boiling is predominantly based on the Eulerian-Eulerian two-fluid approach. Within this framework, wall boiling is accounted for via the Rensselaer Polytechnic Institute (RPI) model and, within this model, the bubble is characterized using three main parameters: departure diameter (D), nucleation site density (N), and departure frequency (f). Typically, the magnitudes of these three parameters are obtained from empirical correlations. However, in recent years, efforts have been directed toward mechanistic modeling of the boiling process. Of the three parameters mentioned above, the departure diameter (D) is least affected by the intrinsic uncertainties of the nucleate boiling process. This feature, along with its prominence within the RPI boiling model, has made it the primary candidate for mechanistic modeling ventures. Mechanistic modeling of D is mostly carried out through solving of force balance equations on the bubble. Forces incorporated in these equations are formulated as functions of the radius of the bubble and have been developed for, and applied to, low-pressure conditions only. Conversely, for high-pressure conditions, no mechanistic information is available regarding the growth rates of bubbles and the forces acting on them. In this study, we use direct numerical simulation coupled with an interface tracking method to simulate bubble growth under high (up to 45 bar) pressure, to obtain the kind of mechanistic information required for an RPI-type approach. In this study, we compare the resulting bubble growth rate curves with predictions made with existing experimental data.

• KSBB Journal
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• v.7 no.1
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• pp.59-65
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• 1992

Hydrodynamics and mixing characteristics such as circulation time, mixing time, circulation velocity and axial dispersion coefficient were investigated using highly viscous pseudoplastic solutions of carboxymethyl cellulose(CMC) in an external circulation loop air-lift reactor with 13$\ell$ working volume. The superficial gas velocity was changed from 1.9 to 6.2cm/s and CMC concentration from 0 to 1.0wt%. The theoretical model based on the pressure balance is developed mathematically to predict liquid circulation velocity. Gas hold-up, circulation velocity and axial dispersion coefficient of liquid phase increased with increasing gas velocity and decreased slightly with increasing liquid viscosity. Mixing time and circulation time decreased with increasing gas velocity and increased with increasing liquid viscosity. Experimental data on liquid circulation velocity were in good agreement with the predicted values.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.5
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• pp.259-268
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• 2017

This paper proposes a hydrogen-based social economy derived from fuel cells capable of replacing fossil fuels and resolving global warming, It thus provides an entry for developing economically feasible social configurations to make use of bio-hydrogen production systems. Bio-hydrogen production works from the principle that microorganisms decompose water in the process of converting CO to $CO_2$, thereby producing hydrogen. This study parts from an analysis of an existing 157-ton class NA1 bio-hydrogen reactor that identifies the state of feedstock and reactor conditions. Based on this analysis, we designed a 1-ton class bio-hydrogen reactor process simulator. We carried out thermal analyses of biological heat reactions, sensible heat, and heat radiation in order to calculate the thermal load of each system element. The reactor temperature changes were determined by modeling the feed mixing tank capacity, heat exchange, and heat storage tank. An analysis was carried out to confirm the condition of the feed mixing tank, heat exchanger, heat storage tank capacity as well as the operating conditions of the system so as to maintain the target reactor temperature.

• Molecules and Cells
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• v.40 no.3
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• pp.211-221
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• 2017

Transforming growth factor ${\beta}1$ $(TGF{\beta}1)/Smad4$ signaling plays a pivotal role in maintenance of the dynamic balance between bone formation and resorption. The microRNA miR-155 has been reported to exert a significant role in the differentiation of macrophage and dendritic cells. The goal of this study was to determine whether miR-155 regulates osteoclast differentiation through $TGF{\beta}1/Smad4$ signaling. Here, we present that $TGF{\beta}1$ elevated miR-155 levels during osteoclast differentiation through the stimulation of M-CSF and RANKL. Additionally, we found that silencing Smad4 attenuated the upregulation of miR-155 induced by $TGF{\beta}1$. The results of luciferase reporter experiments and ChIP assays demonstrated that $TGF{\beta}1$ promoted the binding of Smad4 to the miR-155 promoter at a site located in 454 bp from the transcription start site in vivo, further verifying that miR-155 is a transcriptional target of the $TGF{\beta}1/Smad4$ pathway. Subsequently, TRAP staining and qRT-PCR analysis revealed that silencing Smad4 impaired the $TGF{\beta}1$-mediated inhibition on osteoclast differentiation. Finally, we found that miR-155 may target SOCS1 and MITF to suppress osteoclast differentiation. Taken together, we provide the first evidence that $TGF{\beta}1/Smad4$ signaling affects osteoclast differentiation by regulation of miR-155 expression and the use of miR-155 as a potential therapeutic target for osteoclast-related diseases shows great promise.

• International Journal of Aeronautical and Space Sciences
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• v.13 no.1
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• pp.117-125
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• 2012

This paper presented the design of SRPS, ground function test, and the deployment test on a high speed taxi of KC-100 airplane. KAI has developed a spin recovery system in collaboration with Airborne Systems for KC-100 general aviation airplane. Spin mode analysis, rotary balance and forced oscillation tests were performed to obtain the rotational, dynamic derivatives in the preliminary design phase. Prior to the detailed design process of SRPS, approximations for initial estimation of design parameters- fineness ratio, parachute porosity, parachute canopy filling time, and deployment method- were considered. They were done based on the analytical disciplines such as aerodynamics, structures, and stability & control. SRPS consists of parachute, tractor rocket assembly for deployment, attach release mechanism (ARM) and cockpit control system. Before the installation of SRPS in KC-100 airplane, all the control functions of this system were demonstrated by using SBTB(System Breakout Test Box) in the laboratory. SBTB was used to confirm if it can detect faults, and simulate the firing of pyrotechnic devices that control the deployment and jettison of SRPS. Once confirmed normal operation of SRPS, deployment and jettison of parachute on the high speed taxiing were performed.