• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.9 no.1
• /
• pp.214-220
• /
• 2008

This study aims to design a digital portfolio assessment system in ubiquitous computing(DPASUbi). To achieve that goal, the following issues were worked: Review of various theoretical discussions on portfolio and an analysis of existing programs to select elements to be included in the DPASUbi. Educational evaluation scenarios for the DPASUbi were developed based on the elements. The system was designed on reflecting these elements, that is, learning activities, assessment and usage of portfolio, ubiquitous technology and database. This system will provide guidance on what methods and assessment procedures should be applied in the ubiquitous computing environment totally different from the conventional one. Also, The new system will be helpful in indicating what kind of techniques should be required in the real educational evaluation.

• International Journal of Aeronautical and Space Sciences
• /
• v.18 no.4
• /
• pp.709-718
• /
• 2017

This paper proposes the guidance laws for an agile turn of air-to-air missiles during the initial boost phase. Optimal solution for the agile turn is obtained based on the optimal control theory with a simplified missile dynamic model. Angle-of-attack command generating methods for completion of agile turn are then proposed from the optimal solution. Collision triangle condition for non-maneuvering target is reviewed and implemented for update of terminal condition for the agile turn. The performance of the proposed method is compared with an existing homing guidance law and the minimum-time optimal solution through simulations under various initial engagement scenarios. Simulation results verify that transition to homing phase after boost phase with the proposed method is more effective than direct usage of the homing guidance law.

• Journal of Astronomy and Space Sciences
• /
• v.15 no.1
• /
• pp.251-260
• /
• 1998

We consider the motion of the subsystems as separate bodies as well as the entire satellite for the attitude and orbit control of a communication satellite by multi-body modeling technique. Thus, the system, can be applied to a general communication satellite as well as a specific communication satellite, i. e. Koreasat I,II. The simulation results can be viewed by two-dimensional graphics and three-dimensional animation. The graphical user interface(GUI) makes its usage much simpler. We have simulated a couple of scenarios for Koreasat I,II which are being operated as geostationary communication satellites to verify the system performance.

• Journal of Korea Multimedia Society
• /
• v.10 no.4
• /
• pp.470-482
• /
• 2007

In this paper, we classify next generation mobile communications services into service categories and develop service evolution scenarios for developing the next generation mobile communications service roadmap in NGMC Forum. Firstly, Service categories are defined based on the purpose of service usage. Secondly, the services are classified into the categories and their relationship is analyzed. The candidates of services to be classified and analyzed include all kinds of services discussed in a conceptual level as well as current mobile/Internet services. Finally, we develop a service evolution scenario in each service category. When the next generation service road map is developed based on the results of this paper, it is expected to secure the initiative and enhance the competitive edge in the field of the next generation mobile communications.

• Journal of Korea Multimedia Society
• /
• v.10 no.7
• /
• pp.869-881
• /
• 2007

In this paper, storing and removing method of broadcasting content is proposed for personalized consumption. The main objective of this paper is to keep personalized information, such as additional contents, user creation data, usage history, with broadcasting content, and user can consume broadcasting content to accommodate individual preference. Consequently, proposed file format in this paper is based on MPEG-4 and MPEG-21 file format because they can access and extract data within file format easily and can keep spatiotemporal relation between data. In addition, TV-Anytime metadata is used for program description metadata. Finally, proposed method is verified with file format player and useful application scenarios.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.14 no.6
• /
• pp.2377-2397
• /
• 2020

Human activity recognition is widely used in smart homes, health care and indoor monitor. Traditional approaches all need hardware installation or wearable sensors, which incurs additional costs and imposes many restrictions on usage. Therefore, this paper presents a novel device-free activities recognition system based on the advanced wireless technologies. The fine-grained information channel state information (CSI) in the wireless channel is employed as the indicator of human activities. To improve accuracy, both amplitude and phase information of CSI are extracted and shaped into feature vectors for activities recognition. In addition, we discuss the classification accuracy of different features and select the most stable features for feature matrix. Our experimental evaluation in two laboratories of different size demonstrates that the proposed scheme can achieve an average accuracy over 95% and 90% in different scenarios.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.8 no.7
• /
• pp.2231-2245
• /
• 2014

Cognitive Radio (CR) has very promising potential to improve spectrum utilization by allowing unlicensed Secondary Users (SUs) to access the spectrum dynamically without disturbing licensed Primary Users (PUs). Mitigating interference is a fundamental problem in CR scenarios. This is particularly problematic for deploying CR in cellular networks, when users are located at the cell edge, as the inter-cell interference mitigation and frequency reuse are critical requirements for both PUs and SUs. Further cellular networks require higher cell edge performance, then SUs will meet more challenges than PUs. To solve the performance decrease for SUs at the cell edge, a novel Dynamic Spectrum Allocation (DSA) scheme based on Game Theory is proposed in this paper. Full frequency reuse can be realized as well as inter-cell interference mitigated according to SUs' sensing, measurement and interaction in this scheme. A joint power/channel allocation algorithm is proposed to improve both cell-edge user experience and network performance through distributed pricing calculation and exchange based on game theory. Analytical proof is presented and simulation results show that the proposed scheme achieves high efficiency of spectrum usage and improvement of cell edge SUs' performance.

• Environmental and Resource Economics Review
• /
• v.25 no.2
• /
• pp.299-320
• /
• 2016

This study estimates an energy efficiency of 16 metropolitans and provinces in Korea, and measures potential energy-saving and carbon emission reduction using a non-radial data envelopment analysis method. Based on energy mix scenarios, this study also evaluates the impact of changes in energy structural adjustment on a regional environmental performance. The empirical results show that, on average, 12.70% of energy consumption and 13.73% of carbon emission can be reduced by improvement in energy efficiency, and low efficiency of oil usage in metropolitan cities is a major source of the inefficiency. Furthermore, it is found that energy mix policy should be considered to achieve an extra energy-saving and carbon reduction.

• Korean Journal of Construction Engineering and Management
• /
• v.14 no.4
• /
• pp.15-23
• /
• 2013

Because that construction project is usually uncertain and the plan of it changes frequently, it is difficult to make a reliable and feasible plan for it. As the BIM technology is developed, we can simulate the future of the construction project visually and make more reliable plan. However, data production efficiency is not so high, it is used just for animation and presentation usage. Although, a lot of construction simulation systems are developed, it is difficult to measure performance of them. In this study, we defined the construction simulation work process and the scenarios to measure performance of them. The performance measurement method using simulation process scenario can make possible benchmark test of them.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.11 no.2
• /
• pp.765-781
• /
• 2019

This study predicts the power consumption of an Electric Propulsion Ship (EPS) in marine environment. The EPS is driven by a propeller rotated by a propulsion motor, and the power consumption of the propeller changes by the marine environment. The propulsion motor consumes the highest percentage of the ships' total power. Therefore, it is necessary to predict the power consumption and determine the power generation capacity and the propeller capacity to design an efficient EPS. This study constructs a power estimation simulator for EPS by using a ship motion model including marine environment and an electric power consumption model. The usage factor that represents the relationship between power consumption and propulsion is applied to the simulator for power prediction. Four marine environment scenarios are set up and the power consumed by the propeller to maintain a constant ship speed according to the marine environment is predicted in each scenario.