• The Journal of the Korea Contents Association
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• v.11 no.4
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• pp.414-427
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• 2011

The Means-end theory has successfully been applied in academics circles and is one of the qualitative methodologies, aiming at classifying into groups based on the specific values that they pursue. The more specific purposes of this study is to identify the relationship between the levels of abstraction and HVM(Hierarchical Value Map) and to identify the statistical changes in frequency activated cell and ladders among A-C-V. And lastly, to suggest the HVM according to the levels of abstraction. The subjects of this study includes the 100 hikers who joined the hiking at least once a year for 2007. The results of analysis show that as the level of abstraction goes up, the HVM itself is depicted more simple and the loss of information is also occurred. Consequently, the decision of levels of abstraction is should be made on the basis of objective validity.

• Korean Journal of Optics and Photonics
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• v.10 no.1
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• pp.27-31
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• 1999

We designed and fabricated a monocolor holographic reflector for reflective LCDs with DuPont holographic photopolymer as a holographic recording media. By recording at 514 nm as holographic operating wavelength, it was possible to get the brightest image in green color. High contrast ratio is possible due to misalignment of the images with surface reflection and we achieved on/off contrast ratio of 6:1 by applying the fabricated holographic reflector to a TN-LC cell.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.1138-1144
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• 2008

To study the feasibility of applying wireless communication technology to the control of train for the effective control of train and for the reduction of cost and time to construct the necessary infra structure, we investigate into the application of the existing commercial WCDMA network to CBTC (communication-based train control) to grasp the obstacles and propose the solutions to circumvent them. The obstacles can be categorized into the hand-off problem, the interference problem near the stations, and the problem of radio shadow areas. We propose, as solutions, the cell overlap method and multi-terminal approach for the hand-off problem, the cell sectoring method for the interference problem, and establishment of new base stations along the railroad both to provide the wireless train control and communication service to the customers on the train which was otherwise impossible because of the shadowing effect.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.8B
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• pp.904-909
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• 2011

Cell zooming adjusts the cell range of base stations depending on traffic condition. The cell zooming can be implemented by the adjustment of antenna angles, the clustering of the base stations, and the cell relay. The base stations can adjust the cell range in term of energy efficiency, which can then reduce the overall energy consumption of cellular networks. There is, however, a trade-off between the energy savings and the blocking probability of user calls. A periodic scheme that manages the cell zooming of the base stations was proposed but it was inadequate for dealing with the dynamic nature of traffic patterns. This paper proposes a semi-periodic cell zooming scheme along with the algorithms that select such base stations and define the operation procedure. Simulation results show that the proposed method outperforms the existing scheme in terms of the energy savings without the degradation of the blocking probability.

• Journal of the Korean Electrochemical Society
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• v.9 no.3
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• pp.118-123
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• 2006

Degradation of polymer electrolyte membrane fuel cell (PEMFC) that is facilitated by on/off cycles is one of the most important issues for commercialization of fuel cell vehicles. When a PEMFC stack is shut down, residual hydrogen and induce high voltage equivalent to open circuit voltage to the cathode side that might cause sintering of Pt catalyst and facilitate formation of hydrogen peroxide at the anode side that might decompose $Nafionc\'{A}$ membrane. In this study, degradation of PEMFC exposed to repetitive on/off cycles was investigated by measuring i-V characteristics, ac impedance, cyclic voltammograms, gas leak, cross-sectional SEM images, and TEM images. To prevent degradation of PEMFC caused by the residual gases, hydrogen was removed from anode gas channel by gas-purging and by using a dummy resistance, that were found to be a very effective method.

• Journal of Marine Bioscience and Biotechnology
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• v.7 no.2
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• pp.52-57
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• 2015

The purpose of this study was to investigate a relationship between ultraviolet radiation and initial cell density (ICD) of microalgae using a floating marine photobioreactor (PBR). To examine the effect of ultraviolet (UV) radiation in sunlight on biomass productivity as a function of ICD, 0.5-L floating PBRs covered with or without UV cut-off film were placed in an outdoor rectangular tank containing 200 L of water. At the lower ICDs, 0.01 and 0.05 g/L, biomass productivities in the PBRs without UV cut-off film decreased by $278{\pm}21%$ and $222{\pm}3%$ compared with those with the film, respectively. In contrast, the presence of UV cut-off film did not have a significant effect on biomass productivities at the higher ICDs, 0.25 and 1.25 g/L. When the differences in biomass productivity made by the UV cut-off film were plotted against the sum of cell projection area per light receiving area of the PBR, the results revealed that the inhibitory effect of UV on biomass productivity can be negligible when the sum of cell projection area is equal to the light receiving area of the PBR. These results show that photoinhibition caused by UV radiation could be eliminated via operating the PBR with a proper ICD.

• KSBB Journal
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• v.6 no.3
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• pp.263-270
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• 1991

The optimal cell concentration and dilution rate for maximum ethanol productivity were obtained using dynamic simulation in cell recycled continuous bioreactor. The good control performance was observed using rule-based STR (self-tuning regulator) compared to conventional STR. Rule-base contained the scheme to implement the STR in an efficient on-off way and the scheme for the controlled variable to reach the optimal value in a short time. Since a mathematical model was used to analyze and estimate the changes of the state variables and the parameters, it was possible to understand the physical meaning of the system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.12
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• pp.1135-1144
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• 2013

Deploying small cells is a reliable and influential solution to handle the skyrocketing traffic increase in the cellular network, and the small cell technology is evolving to ultra-dense network (UDN). In this paper we propose a small cell on/off algorithm with a simple but essential framework composed of access point (AP), user equipment (UE), and small cell controller (SCC). We propose Device-Assisted Networking for Cellular grEening (DANCE) algorithms that save the energy consumption by tying to minimize the number of turned-on APs while maintaining the network throughput. In doing so, SCC firstly gathers the feedback messages from UEs and then makes a decision including a set of turned-on APs and user association. DANCE algorithm has several variations depending on the number of bits of the UE's feedback message (1 bit vs. N bit), and is divided into AP-first, UE-first, or Proximity ON according to the criteria of selecting the turned-on APs. We perform extensive simulations under the realistic UDN environment, and the results confirm that the proposed algorithms, compared to the baseline, can significantly enhance the energy efficiency, e.g., more than a factor of 10.

• Journal of Internet Computing and Services
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• v.19 no.2
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• pp.9-15
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• 2018

This paper proposes an energy efficient adaptive relay station ON/OFF scheme with different frequency reuse factors (FRFs) to enhance the system throughput and reduce the transmission energy consumption for the transparent mode of 2-hop cellular relay networks (CRNs) based on orthogonal frequency division multiple access and time division duplex. In the proposed scheme, the base station turns on or off the relay stations (RSs) when they are overutilized and undertuilized based on the traffic density of the cell coverage, respectively. Through the simulation results, we show that the proposed scheme outperforms the conventional CRN in terms of the energy consumption with the same system throughput. Further, in order to increase the system throughput with low energy consumption, the best way is FRF 1 when the number of operating RSs is up to 4 and FRF 2 otherwise.

• Journal of KIISE:Information Networking
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• v.31 no.5
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• pp.482-489
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• 2004

Paging extensions for Mobile IP was proposed to avoid unnecessary registration signaling overhead of Mobile IP. In order to support the paging function in Mobile IP, the slates of a mobile node arc divided into active on, active off, idle. The active on state means when any incoming or outgoing data session arrives to a mobile node. After data session is completed, the state of the motile node is changed into active off from active on. At this moment, the active timer starts to be operated. If the active timer expires, the mobile node moves to idle state. If a mobile node has very frequently data sessions at the same cell, the mobile node is better to move slowly into idle state. The other way, if the mobile node very frequently moves into new cell area and receives or sends little data, the mobile node is better to move earlier into idle state. In this raper, the active timer is adaptively set by the mobile nodes traffic and mobility characteristics and the paging scheme using this active timer is proposed to reduce the location registration cost.