• International Journal of Computer Science & Network Security
• /
• v.24 no.3
• /
• pp.71-82
• /
• 2024

This paper proposes a new communication system for e-learning applications to mitigate the negative impacts of COVID-19 where the online massive demands impact the current commu-nications systems infrastructures and capabilities. The proposed system utilizes high-altitude platforms (HAPs) for fast and efficient connectivity provision to bridge the communication in-frastructure gap in the current pandemic. The system model is investigated, and its performance is analyzed using adaptive antenna arrays to achieve high quality and high transmission data rates at the student premises. In addition, the single beam and multibeam HAP radio coverage scenarios are examined using tapered uniform concentric circular arrays to achieve feasible communication link requirements.

• Journal of Korea Water Resources Association
• /
• v.42 no.12
• /
• pp.1091-1102
• /
• 2009

This study developed an integrated approach to climate change and urbanization impact assessment by linking models of SDSM (statistical downscaling model), HSPF (hydrological simulation program?Fortran) and ICM (impervious cover model). A case study of the Anyangcheon watershed illustrated how the proposed framework can be used to analyze the impacts of climate change and urbanization in terms of flood control, water security and water quality. The evaluation criteria were the variations of flow and pollutant concentration duration curves. In this study, nine scenarios including three climate (present condition, A1B and A2) and three urbanization scenarios were analyzed using HSPF model. As a result, climate change is a large influence on the flowrate and the urbanization affects the pollutant concentration. Therefore, the impacts of both climate change and urbanization must be included into the watershed management and water resources planning for sustainable development.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.12 no.6
• /
• pp.2595-2618
• /
• 2018

In this paper, we investigate secure communication with the presence of multiple eavesdroppers (Eves) in a two-tier downlink dense heterogeneous network, wherein there is a macrocell base station (MBS) and multiple femtocell base stations (FBSs). Each base station (BS) has multiple users. And Eves attempt to wiretap a macrocell user (MU). To keep Eves ignorant of the confidential message, we propose a physical-layer security scheme based on cross-layer cooperation to exploit interference in the considered network. Under the constraints on the quality of service (QoS) of other legitimate users and transmit power, the secrecy rate of system can be maximized through jointly optimizing the beamforming vectors of MBS and cooperative FBSs. We explore the problem of maximizing secrecy rate in both non-colluding and colluding Eves scenarios, respectively. Firstly, in non-colluding Eves scenario, we approximate the original non-convex problem into a few semi-definite programs (SDPs) by employing the semi-definite relaxation (SDR) technique and conservative convex approximation under perfect channel state information (CSI) case. Furthermore, we extend the frame to imperfect CSI case and use the Lagrangian dual theory to cope with uncertain constraints on CSI. Secondly, in colluding Eves scenario, we transform the original problem into a two-tier optimization problem equivalently. Among them, the outer layer problem is a single variable optimization problem and can be solved by one-dimensional linear search. While the inner-layer optimization problem is transformed into a convex SDP problem with SDR technique and Charnes-Cooper transformation. In the perfect CSI case of both non-colluding and colluding Eves scenarios, we prove that the relaxation of SDR is tight and analyze the complexity of proposed algorithms. Finally, simulation results validate the effectiveness and robustness of proposed scheme.

• Information Systems Review
• /
• v.10 no.2
• /
• pp.21-48
• /
• 2008

The Korean on-line game industry is going through a rapid change. The future business environments for potential on-line game companies are very uncertain due to the new service and the different market trends. In this paper, I propose the use of morphological analysis approach for scenario generation about the future of the On-line game industry. The stages of research process were as follows; Firstly, digital contents analysis and key issues were drawn on IPTV in the on-line game industry. Secondly, each key issue was analyzed and the influence factors and directivity flow were found. Thirdly, highly probable future on-line game industry scenarios were derived. In this case, morphological analysis. On the basis of the developed scenarios, I formulated some implications for business strategy of a potential on-line game companies.

• Science of Emotion and Sensibility
• /
• v.10 no.4
• /
• pp.555-569
• /
• 2007

Ubiquitous computing environment is the new surroundings, currently being realized by modern technology. Since previous usability tests are not suitable for this new technological environment, new research on psychological factors needs to be conducted. The evaluation of service scenarios also will be required in tandem with traditional usability tests of operation devices. Consequently, this study classified usability factors from a scenario perspective and was conducted with a focus on the psychological elements of controllability from a mechanical perspective. Study 1 reclassified the factors of existing usability tests according to similarity and application scenarios, and ten important groups of factors were newly created. Study 2 focused specifically on the design side of a device and showed that the degree of familiarity with the ubiquitous computing device and its complexity brought about a difference in perceived controllability of the device.

• Atmosphere
• /
• v.27 no.2
• /
• pp.189-197
• /
• 2017

Progressing from weather forecasts and warnings to multi-hazard impact-based forecast and warning services represents a paradigm shift in service delivery. Urban flooding is a typical meteorological disaster. This study proposes support plan for urban flooding impact-based forecast by providing inundation risk matrix. To achieve this goal, we first configured storm sewer management model (SWMM) to analyze 1D pipe networks and then grid based inundation analysis model (GIAM) to analyze 2D inundation depth over the Gangnam drainage area with $7.4km^2$. The accuracy of the simulated inundation results for heavy rainfall in 2010 and 2011 are 0.61 and 0.57 in POD index, respectively. 20 inundation scenarios responding on rainfall scenarios with 10~200 mm interval are produced for 60 and 120 minutes of rainfall duration. When the inundation damage thresholds are defined as pre-occurrence stage, occurrence stage to $0.01km^2$, 0.01 to $0.1km^2$, and $0.1km^2$ or more in area with a depth of 0.5 m or more, rainfall thresholds responding on each inundation damage threshold results in: 0 to 20 mm, 20 to 50 mm, 50 to 80 mm, and 80 mm or more in the rainfall duration 60 minutes and 0 to 30 mm, 30 to 70 mm, 70 to 110 mm, and 110 mm or more in the rainfall duration 120 minutes. Rainfall thresholds as a trigger of urban inundation damage can be used to form an inundation risk matrix. It is expected to be used for urban flood impact forecasting.

• The Journal of the Korea Contents Association
• /
• v.3 no.4
• /
• pp.63-68
• /
• 2003

This paper is to measure the sensitivity of relations in communication network operation. In order to procure an important adequacy in the network operation and quality improvement, it is necessary to increase network operation efficiency and analyze the characteristic of network operation. Finally, we analyze costing appropriate operation, propose profit increase scheme and apply realistic business. First of all it's important to improve and estimate a proper operating cost thoroughly and comprehensively. Because the important issue of this process is quality process and this quality process occurs customers' satisfaction, therefore, to make a mutual relation in-between individual change of each element is to analyze a reasonable standard. So, for this reason we study on structuring nice moods for network operation and estimating many scenarios for measuring efficiency. Especially those in economic and sensitivity based. It will be the development of analyzing methods which suites the service and communication system. The result of this study gives a basis for making a flexible and highly predictable system by pre configured sensitivity analysis of each scenarios.

• Smart Media Journal
• /
• v.3 no.1
• /
• pp.9-15
• /
• 2014

In these days, along with the extreme popularity of online social network services, it becomes an important problem understanding the role of social network in the research of message dissemination. Past studies of message dissemination over online social network services mostly consider the coverage of message dissemination and the methods to maximize it. But, these works lack of the consideration of the impact of multi channel social network, which has multiple communication channel with distinct properties of message transfer and various users with distinct channel preferences. In this paper, the new message dissemination model over multi-modal multi-channel social network, the Delay Weighted Independent Cascade Model, is proposed. The proposed model considers various channels including online social network service, email, SMS messaging, phone and mouth-to-mouth and their distinct message transfer properties. In order to consider the various user properties, the different value of probability of forwarding a message and the different preference of communication channel is considered. Moreover, the proposed model considers the distribution of user location and allows to analyze the properties of message dissemination under various scenarios. Based on the proposed model, a message dissemination simulator is generated and the message disseminations on various scenarios are analyzed.

• The Transactions of the Korea Information Processing Society
• /
• v.7 no.1
• /
• pp.181-199
• /
• 2000

In this paper, we implemented and tested MPOA(MutiProtocol Over ATM) standardized in ATM Forum, which provides service for various layer 3 protocols as well as legacy LAN applications over ATM networks. The functions of MPCs(MPOA Clients) and MPSs(MPOA Servers) which are the components in MPOA systems are implemented. MPCs are located at the edge device and MPOA hosts and MPSs exist in routers. The implemented MPCs have the functions such as exchances of primitives between an LEC(LAN Emulation Client) and an MPC, management and maintenance of Egress/Ingress cache, default transmission through LECs and shortcut transmission. Assuming that routing, convergence and NHRP(Next Hop Resolution Protocol) functions exist in routers, the implemented MPSs have the functions such as exchanges of primitives between an LEC and an MPC, conversion and exchanges of frames between MPOA and NHRP, and management and maintenance of Egress/Ingress cache. All of the possible scenarios are made up to test whether they run correctly. The implemented system is tested by simulation according to the scenarios.

• Broadcasting and Media Magazine
• /
• v.11 no.4
• /
• pp.118-131
• /
• 2006

With rapid development in ultra fast communication and digital multimedia, the realistic broadcasting technology, that can stimulate five human senses beyond the conventional audio-visual service is emerging as a new generation broadcasting technology. In this paper, we introduce a haptic broadcasting system and related core system and component techniques by which we can 'touch and feel' objects in an audio-visual scene. The system is composed of haptic media acquisition and creation, contents authoring, in the haptic broadcasting, the haptic media can be 3-D geometry, dynamic properties, haptic surface properties, movement, tactile information to enable active touch and manipulation and passive movement following and tactile effects. In the proposed system, active haptic exploration and manipulation of a 3-D mesh, active haptic exploration of depth video, passive kinesthetic interaction, and passive tactile interaction can be provided as potential haptic interaction scenarios and a home shopping, a movie with tactile effects, and conducting education scenarios are produced to show the feasibility of the proposed system.