• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.3
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• pp.997-1005
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• 2010

Recently, there has been a growing interest in the use of WLAN technology due to its easy deployment, flexibility and so on. Examples of WLAN applications range from standard internet services such as Web access to real-time services with strict latency/throughput requirements such as multimedia video and voice over IP on wireless network environments. Fair and efficient distribution of the traffic loads among APs(Access Points) has become an important issue for improved utilization of WLAN. This paper focuses on an AP selection scheme for achieving better load balance, and hence increasing network resource utilization for each user on wireless network environments. This scheme makes use of active scan patterns and the network delay as main parameters of load measurement and AP selection. This scheme attempts to estimate the AP traffic loads by observing the up/down delay and utilize the results to maximize the link resource efficiency through load balancing. We compared the proposed scheme with the original SNR(Signal to Noise Ratio)-based scheme using the NS-2(Network Simulation.2). We found that the proposed scheme improves the throughput by 12.5% and lower the network up/down link delay by 36.84% and 60.42%, respectively. All in all, the new scheme can significantly increase overall network throughput and reduce up/down delay while providing excellent quality for voice and video services.

• Journal of Internet Computing and Services
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• v.19 no.3
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• pp.67-77
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• 2018

This paper suggests that LOD establishes its own link policy and publishes it to LOD cloud to provide identity among entities in different LODs. For specifying the link policy, we proposed vocabulary set founded on RDF model as well. We implemented Policy based In-depth Searching and Cleansing(PISC for short) system that proceeds in-depth searching across LODs by referencing the link policies. PISC has been published on Github. LODs have participated voluntarily to LOD cloud so that degree of the entity identity needs to be evaluated. PISC, therefore, evaluates the identities and cleanses the searched entities to confine them to that exceed user's criterion of entity identity level. As for searching results, PISC provides entity's detailed contents which have been collected from diverse LODs and ontology customized to the content. Simulation of PISC has been performed on DBpedia's 5 LODs. We found that similarity of 0.9 of source and target RDF triples' objects provided appropriate expansion ratio and inclusion ratio of searching result. For sufficient identity of searched entities, 3 or more target LODs are required to be specified in link policy.

• Information Systems Review
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• v.21 no.1
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• pp.135-152
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• 2019

Recently there are many development and support policies for start-up companies because of successful venture companies related to ICT services. However, as these policies have focused on the support for the initial stage of start-up, many start-up companies have difficulties to continuously grow up. The main reason for these difficulties is that they recognize start-up tasks as independent activities. However, many experts or related articles say that start-up tasks are composed of related processes from the initial stage to the stable stage of start-up firms. In this study, we models the start-up processes based on the survey collected by the start-up companies, and analyze the start-up process of ICT service companies with process mining techniques. Through process mining analysis, we can draw a sequential flow of tasks for start-ups and the characteristics of them. The analysis of start-up businessman, idea derivation, creating business model, business diversification processes are resulted as important processes, but marketing activity and managing investment funds are not. This result means that marketing activity and managing investment funds are activities that need ongoing attention. Moreover, we can find temporal and complementary tasks which could not be captured by independent individual-level activity analysis. Our process analysis results are expected to be used in simulation-based web-intelligent system to support start-up business, and more cumulated start-up business cases will be helpful to give more detailed individual-level personalization service. And our proposed process model and analyzing results can be used to solve many difficulties for start-up companies.

• Journal of Bio-Environment Control
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• v.31 no.4
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• pp.485-496
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• 2022

Modern agriculture is being transformed into smart agriculture to maximize production efficiency along with changes in the 4th industrial revolution. However, rural areas in Korea are facing challenges of aging, low fertility, and population outflow, making it difficult to transition to smart agriculture. Among ICT technologies, simulation allows users to observe or experience the results of their choices through imitation or reproduction of reality. The combination of the three-dimension (3D) model and the greenhouse simulator enable a 3D experience by virtual greenhouse for fruits and vegetable cultivation. At the same time, it is possible to visualize the greenhouse under various cultivation or climate conditions. The objective of this study is to apply the greenhouse climate management model for simulation development that can visually see the state of the greenhouse environment under various micrometeorological properties. The numerical solution with the mathematical model provided a dynamic change in the greenhouse environment for a particular greenhouse design. Light intensity, crop transpiration, heating load, ventilation rate, the optimal amount of CO₂ enrichment, and daily light integral were calculated with the simulation. The results of this study are being built so that users can be linked through a web page, and software will be designed to reflect the characteristics of cladding materials and greenhouses, cultivation types, and the condition of environmental control facilities for customized environmental control. In addition, environmental information obtained from external meteorological data, as well as recommended standards and set points for each growth stage based on experiments and research, will be provided as optimal environmental factors. This simulation can help growers, students, and researchers to understand the ICT technologies and the changes in the greenhouse microclimate according to the growing conditions.

• Information Systems Review
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• v.15 no.3
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• pp.1-37
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• 2013

This study is conducted to explore the possibility of service convergence to promote mobile learning. This study has attempted to identify how mobile learning service is provided, which services among them are considered most popular, and which services are highly demanded by users. This study has also investigated the potential opportunities for service convergence of mobile service and e-learning. This research is then extended to examine the possibility of active convergence of common services in mobile services and e-learning. Important variables have been identified from related web pages of portal sites using social network analysis (SNA) and association rules. Due to the differences in number and type of variables on different web pages, SNA was used to deal with the difficulties of identifying the degree of complex connection. Association analysis has been used to identify association rules among variables. The study has revealed that most frequent services among common services of mobile services and e-learning were Games and SNS followed by Payment, Advertising, Mail, Event, Animation, Cloud, e-Book, Augmented Reality and Jobs. This study has also found that Search, News, GPS in mobile services were turned out to be very highly demanded while Simulation, Culture, Public Education were highly demanded in e-learning. In addition, It has been found that variables involving with high service convergence based on common variables of mobile and e-learning services were Games and SNS, Games and Sports, SNS and Advertising, Games and Event, SNS and e-Book, Games and Community in mobile services while Games, Animation, Counseling, e-Book, being preceding services Simulation, Speaking, Public Education, Attendance Management were turned out be highly convergent in e-learning services. Finally, this study has attempted to predict possibility of active service convergence focusing on Games, SNS, e-Book which were highly demanded common services in mobile and e-learning services. It is expected that this study can be used to suggest a strategic direction to promote mobile learning by converging mobile services and e-learning.

• Journal of Korea Multimedia Society
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• v.7 no.8
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• pp.1066-1077
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• 2004

Dramatic increase in the number of Internet users want highly qualified service of continuous media contents on the web. To solve these problems, we present two network caching schemes(PPC, PPCwP) which consider the characteristics of continuous media objects and user access pattern in this paper. While there are plenty of reasons to create rich media contents, delivering this high bandwidth contents over the internet presents problems such as server overload, network congestion and client-perceived latency. PPC scheme periodically calculates the popularity of objects based on the playback quantity and determines the optimal size of the initial fraction of a continuous media object to be cached in proportion to the calculated popularity. PPCwP scheme calculates the expected popularity using the series information and prefetches the expected initial fraction of newly created continuous media objects. Under the PPCwP scheme, the initial client-perceived latency and the data transferred from a remote server can be reduced and limited cache storage space can be utilized efficiently. Trace-driven simulation have been performed to evaluate the presented caching schemes using the log-files of iMBC. Through these simulations, PPC and PPCwP outperforms LRU and LFU in terms of BHR and DSR.

• Journal of the Korean Association of Geographic Information Studies
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• v.20 no.1
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• pp.98-112
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• 2017

Recently, various research has been conducted on the use of a game engine instead of a commercial geographic information system (GIS) engine for the development of 3D GIS. The advantage of the 3D game engine is that it allows developers to develop various modules according to their abilities. In particular, in the area of disasters, a wide range of alternatives for prevention as well as prediction can be presented when new analyses are attempted by combining geographic information and disaster-related information. Furthermore, 3D analysis can be an important factor in analyzing the phenomena occurring in the real 3D world because of the nature of disasters. Therefore, in this study, we tried to develop a visualization module for flood disaster information through a 3D game engine by considering the solutions for cost and manpower problems and the degree of freedom of development. Raw flood data was mapped onto spatial information and interpolation was performed for the natural display of the mapped flood information. Furthermore, we developed a module that intuitively shows dangerous areas to users by generating cumulative information in order to display multidimensional information based on this information. The results of this study are expected to enable various flood information analyses as well as quick response and countermeasures to floods.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.7
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• pp.56-64
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• 2012

A smart grid is the next generation power grid which combines the existing power grid with information technology, so an energy efficient power grid can be provided. In this paper, in order to build an efficient smart grid an AMI system, which gears with the existing home network and provides an user friendly management function, is proposed. The proposed AMI system, which is based on an extended home network, consists of various functional units; smart meters, communication modules, home gateway, security modules, meter data management modules (MDMM), electric power application modules and so on. The proposed home network system, which can reduce electric power consumption and transmit data more effectively, is designed by using IEEE 802.15.4. The extended home gateway can exchange energy consumption information with the outside management system via web services. The proposed AMI system is designed to enable two-way communication between the home gateway and MDMM via the Internet. The AES(Advanced Encryption Standard) algorithm, which is a symmetric block cipher algorithm, is used to ensure secure information exchange. Even though the results in this study could be limited to our experimental environment, the result of the simulation test shows that the proposed system reduces electric power consumption by 4~42% on average compared to the case of using no control.

• Archives of design research
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• v.18 no.1 s.59
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• pp.17-26
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• 2005

Nowadays, display-contents are developing to an informative environment. that is under the logic of the media operating system. To perceive the media-environments and produce the cultural contents, the cultural designers seek to understand a skin structure from making up for shape. To appreciate operating system in data and database is not only systematization of form and contents of visual contents but also variety contents into multiple-platform and integrative environments. These days, the spectacle exhibition try to express for their surface design between algorithm of data and database. the information is expressing aesthetic which means presents the integrated contents through the play instinct environment to end-user. That was given web or game to participation is developing with the cellular device and ubiquitous computing system. in the linear perspective, the end-user should be immerse more and more hyper-simulation system because of the operating algorithm of database. To do this, human have need to get the information-ability from multi-platform society. In the virtual environment, database offer the experience of an unheard-of event to end-user that prepare the participants the circumstances priority of signifiers. To do that already based on a fixed sensibility endow with narrative of the freshness- experience.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.315-315
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• 2017

In Japan, more than 80 % of soybean growing area is converted fields and excess water is one of the major problems in soybean production. For example, recent study (Yoshifuji et al., 2016) suggested that in the fields of shallow groundwater level (GWL) (< 1m depth), rising GWL even in a short period (e.g. 1 day) causes inhibition of soybean growth. Thus it becomes more and more important to predict GWL and soil moisture in detail. In addition to conventional surface drainage and underdrain, FOEAS (Farm Oriented Enhancing Aquatic System), which is expected to control GWL in fields adequately, has been developed recently. In this study we attempted to predict GWL and soil moisture condition at the converted field with FOEAS in Biwa lake reclamation area, Shiga prefecture, near the center of the main island of Japan. Two dimensional HYDRUS model (Simuinek et al., 1999) based on common Richards' equation, was used for the calculation of soil water movement. The calculation domain was considered to be 10 and 5 meter in horizontal and vertical direction, respectively, with two layers, i.e. 20cm-thick of plowed layer and underlying subsoil layer. The center of main underdrain (10 cm in diameter) was assumed to be 5 meter from the both ends of the domain and 10-60cm depth from the surface in accordance with the field experiment. The hydraulic parameters of the soil was estimated with the digital soil map in "Soil information web viewer" and Agricultural soil-profile physical properties database, Japan (SolphyJ) (Kato and Nishimura, 2016). Hourly rainfall depth and daily potential evapo-transpiration rate data were given as the upper boundary condition (B.C.). For the bottom B.C., constant upward flux, which meant the inflow flux to the field from outside, was given. Seepage face condition was employed for the surrounding of the underdrain. Initial condition was employed as GWL=60cm. Then we compared the simulated and observed results of volumetric water content at depth of 15cm and GWL. While the model described the variation of GWL well, it tended to overestimate the soil moisture through the growing period. Judging from the field condition, and observed data of soil moisture and GWL, consideration of soil structure (e.g. cracks and clods) in determination of soil hydraulic parameters at the plowed layer may improve the simulation results of soil moisture.