• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.6
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• pp.1191-1196
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• 2017

Lately, the three mobile telecom companies in Korea are competing for the launch of Internet of Things services for using home. Typical launched services are in the smart home related fields. However, Internet of Things as mobile telecom based are at an early stage, expected that various services will be started continuously. At this point, we have been planning to analyze the preference of Internet of Things for objects based on the services already launched. In order to apply the analytic hierarchy method, the first stage factors were designed as Safety, Security, Health care, Intelligence and Home appliances. In addition, the second stage factors were organized into 18 detailed services presented in the conceptual model. As a result, Health care (23.2%) was the most preferred priority. These results can be interpreted as the result of interest in health by improving income. We presented the theoretical and practical implications of these results.

• Fire Science and Engineering
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• v.26 no.3
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• pp.79-84
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• 2012

In this study thermal characteristics of heat-responsive element considering conduction, convection and rate of change of element using Response Time Index (RTI) applied to sensitivity test of sprinkler head at home and aborad are theoretically investigated. Analytic solution of temperature distributions with radial direction and time is obtained form energy transport equations, non-homogeneous 2th order partial differential equation, applying to constant wall temperature and symmetric condition in order to analyze thermal characteristics of heat-responsive element for circular cylindrical geometry. Base on the results, the analytic method of this study is fundamental data to practical use for sensitivity test of sprinkler head and design of heat-responsive element.

• Journal of Korean Society of Transportation
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• v.26 no.4
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• pp.195-204
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• 2008

Multi-Criteria Analysis is one method for optimizing decisions that include numerous characteristics and objective functions. The Analytic Hierarchy Process (AHP) is used as a general Multi-Criteria Analysis considering many critical issues. However, since validation procedures for the decision reliability of AHP valuers had been left off existing methodologies, a new methodology including such validation procedures is required to make more reliable decisions. In this research, idea decision results are derived using Monte Carlo Simulation in cases where AHP valuers do not have expertise in the specific project, and these results are compared with the results derived from experts to develop a new analysis model to make more reliable decisions. Finally, this new analysis is applied to various field case studies of road and rail carried out by the Korea Development Institute (KDI) between 2003 and 2006 to validate the new analysis model. The study found that approximately 20% of decisions resulting from the existing methodology are considered prudent. In future studies, the authors suggest analyzing the correlation between initial weights and final results since final results are enormously influenced by the initial weight.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.1
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• pp.35-41
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• 2010

In developing modern aircraft, the reconfiguration control that can improve the safety and the survivability against the unexpected failure by partitioning control surfaces into several parts has been actively studied. This paper deals with the reconfiguration control using model predictive control method considering the saturation of control surfaces under the control surface failure. Linearized aircraft model at trim condition is used as the internal model of model predictive control. We propose the controller that performs optimization using LMI (linear matrix inequalities) based semi-definite programming in case that control surface saturation occurs, otherwise, uses analytic solution of the model predictive control. The performance of the proposed control method is evaluated by nonlinear simulation under the flight scenario of control surface failure.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2000.09a
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• pp.105-115
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• 2000

As large underground projects such as radioactive waste disposal, hot water and heat storage, and geothermal energy become influential, the study, which consider all aspects of thermics, hydraulics and mechanics would be needed. Thermo Hydro-Mechanical coupling analysis is one of the most complex numerical technique because it should be implemented with the combined three governing equations to analyze the behavior of rock mass. In this study, finite element code, which is based on Biot's consolidation theory, was developed to analyze the thermo-hydro-mechanical coupling in continuum rock mass. To verify the implemented program, one-dimensional consolidation model under the isothermal and non-isothermal conditions was analyzed and was compared with the analytic solution. The parametric study on two-dimensional consolidation was also performed and the effects of several factors such as poisson's ratio and hydraulic anisotropy on rock mass behavior were investigated. In the future, this program would be revised to be used for analysis of general discontinuous media with incorporating discrete joint model.

• Tunnel and Underground Space
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• v.10 no.3
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• pp.355-365
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• 2000

As large underground projects such as radioactive waste disposal, hot water and heat storage, and geothermal energy become influential, the study, which consider all aspects of thermics, hydraulics and mechanics would be needed. Thermo-Hydro-Mechanical coupling analysis is one of the most complex numerical technique because it should be implemented with the combined three governing equations to analyze the behavior of rock mass. In this study, finite element code, which is based on Biot's consolidation theory, was developed to analyze the thermo-hydro-mechanical coupling in continuum rock mass. To verify the implemented program, one-dimensional consolidation model under the isothermal and non-isothermal conditions was analyzed and was compared with the analytic solution. The parametric study on two-dimensional consolidation was also performed and the effects of several factors such as poisson's ratio and hydraulic anisotropy on rock mass behavior were investigated. In the future, this program would be revised to be used for analysis of general discontinuous media with incorporating discrete joint model.

• Journal of the Geological Society of Korea
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• v.54 no.6
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• pp.677-682
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• 2018

Magnetic anomalies are sensitive to magnetic properties present in deep Earth and near surface structures. Such geophysical characteristics often can be quantified by numerical analyses. In this study, we developed a finite element method (FEM) approach to compute magnetic anomalies using COMOL $Multiphysics^{(R)}$. This FEM approach was verified by comparing its numerical results with the previously known analytic solution for a uniformly magnetized sphere. Then, we used the method to compute magnetic reversal patterns near mid-ocean ridge with various faulting scenarios. This COMSOL-based approach can be incorporated into advanced multi-physical numerical models to understand the Earth.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.1
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• pp.141-149
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• 2009

In this paper, quasi-static FDTD method is implemented by FORTRAN programming, and it is used for analysis of body induced current in middle frequencies. The quasi-static FDTD program is validated by comparing the calculation result with analytic solution of the test model, to which it is difficult to apply conventional FDTD. It is confirmed that the time-step is reduced by $5.68{\times}10^6$ times. Using validated numerical technique, body induced current distribution in high resolution 3-D human model is calculated for 20[kHz] magnetic field exposure and 1[MHz] electric field exposure. Also, the effect of grounding condition of both feet on the distribution and amplitude of the induced current is analyzed. It is expected that this research can be applied to various fields including safety assessment of body induced current and development of diagnosis devices using bio-electricity.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.18 no.1
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• pp.84-96
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• 2006

This paper presents a simplified numerical method that can be used to incorporate the partial reflection and transmission of water waves in the hyperbolic mild-slope equation. For given reflection and transmission coefficients, wave fields around a porous breakwater including reflection, transmission, and diffraction can be simulated accurately. For the verification of the proposed method, numerical experiments have been carried out and compared with analytic solutions given by Yu(1995) and McIver(1999). The proposed method is easy to implement and is computationally efficient. It is demonstrated that the method performs well with a sloping bottom bathymetry and varying incident wave angles.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.5C
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• pp.486-495
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• 2002

In this paper, we propose a delay reduction method for frame-based packet transmit scheduling algorithm. A high-speed network such as ATM network has to provide some performance guarantees such as bandwidth and delay bound. Framing strategy naturally guarantees bandwidth and enables simple rate-control while having the inherently bad delay characteristics. The proposed delay reduction method uses the same hierarchical frame structure as HRR (Hierarchical Round-Robin) but does not use the static priority scheme such as round-robin. Instead, we use a dynamic priority change scheme so that the delay unfairness between wide bandwidth connection and narrow bandwidth connection can be eliminated. That is, we use FIFO (First-In First-Out) concept to effectively reduce the occurrence of worst-case delay and to enhance delay distribution. We compare the performance for the proposed algorithm with that of HRR. The analytic and simulation results show that HFIFO inherits almost all merits of HRR with fairly better delay characteristics.