• 제어로봇시스템학회:학술대회논문집
• /
• 2005.06a
• /
• pp.700-705
• /
• 2005

The purpose of this project is the derivation and development of techniques for the new estimation of robustness for the systems having uncertainties. The basic ideas to analyze the system which is the originally nonlinear is Lyapunov direct theorems. The nonlinear systems have various forms of terms inside the system equations and this investigation is confined in the form of bounded uncertainties. Bounded means the uncertainties are with same positive/negative range. The number of uncertainties will be the degree of freedoms in the calculation of the stability region. This is so called the robustness bounds. This proposition adopts the theoretical analysis of the Lyapunov direct methods, that is, the sign properties of the Lyapunov function derivative integrated along finite intervals of time, in place of the original method of the sign properties of the time derivative of the Lyapunov function itself. This is the new sufficient criteria to relax the stability condition and is used to generate techniques for the robust design of control systems with structured perturbations. Using this relaxing stability conditions, the selection of Lyapunov candidate function is of various forms. In this paper, the quadratic form is selected. this generated techniques has been demonstrated by recent research interest in the area of robust control design and confirms that estimation of robustness bounds will be improved upon those obtained by results of the original Lyapunov method. In this paper, the symbolic algebraic procedures are utilized and the calculating errors are reduced in the numerical procedures. The application of numerical procedures can prove the improvements in estimations of robustness for one-and more structured perturbations. The applicable systems is assumed to be linear with time-varying with nonlinear bounded perturbations. This new techniques will be extended to other nonlinear systems with various forms of uncertainties, especially in the nonlinear case of the unstructured perturbations and also with various control method.

• Journal of Power Electronics
• /
• v.16 no.2
• /
• pp.631-642
• /
• 2016

Usually, the output characteristics of a photovoltaic (PV) array are significantly affected by non-uniform irradiance which is caused by ambient obstacles, clouds, orientations, tilts, etc. Some local maximum power points (LMPP) in the current-voltage (I-V) curves of a PV array can result in power losses of the array. However, the output power at the global maximum power point (GMPP) is different in different interconnection schemes in a PV array. Therefore, based on the theoretical analysis and mathematical derivation of different topological structures of a PV array, this paper investigated the output characteristics of dual series PV arrays with different interconnections. The proposed mathematical models were also validated by experimental results. Finally, this paper also concluded that in terms of performance, the total cross tied (TCT) interconnection was not always the optimal structure, especially in a dual series PV array. When one of the PV modules was severely mismatched, the TCT worked worse than the series parallel (SP) structure. This research can provide guidance for switching the interconnection to gain the greatest energy yield in a changeable- structure PV system.

• Korean Institute of Interior Design Journal
• /
• v.22 no.1
• /
• pp.231-238
• /
• 2013

As the technical medium evolves, the method of accepting information is changing. The technical medium also appears in various ways through the combination with art. This study aims to conduct research on how hypermedia, appearing from this, will reveal itself in the urban public design in terms of its expression mode. First, this study looks at the characteristics for expression representation of hypermedia art through theoretical considerations on the hypermedia. Second, this study identifies how hypermedia art is introduced in the urban public design through art cases. Third, this study reveals the characteristics depending on the expression mode of hypermedia art shown in the urban public design based on the analyzed cases. As a result, first, hypermedia appeared in various image lighting expression modes that use 'light' in the urban public design and interacted with the public. Second, hypermedia reacted to 'motion' and was the expression mode of using bodies in the urban public design and using peripheral devices and external environment and characterized by having complex patterns of multi-layered structure through multi-media. It also applied sight, hearing, and touch partially or integratedly to attract synesthesia from the public and checked mutual interaction rapidly in an improvised way. Third, such a complex digital technology was the network expression mode beyond space and time by medium of urban public design and characterized by the new experience of virtual space expansion through the world wide network and the communication mode of participation. With such a role change of media and combination with art, hypermedia has been achieving varied extended representations. It is considered to change our monotonous urban environment, restore our relationship with the public, and open a new field of communication. Accordingly, the significance of this study can be identified through how it aimed to display the expression method of hypermedia which caused its extension in the field of urban public design as well as through the derivation of relevant characteristics.

• Journal of Radiation Protection and Research
• /
• v.26 no.4
• /
• pp.357-365
• /
• 2001

Intervention levels for protection of the public in a radiological emergency are theoretically derived by the cost-benefit approach with the concept of justification and optimization. Intervention levels on the sheltering, evacuation, temporary relocation and permanent resettlement for protection of the public are estimated with the cost to protective countermeasures and the value from dose averted which are the site specific parameters. As a result, it is confirmed that IAEA guidelines for intervention levels are applicable to the radiological emergency in Korea. Optimum ranges of 5 - 10 mSv/2days for sheltering, 25 - 130 mSv/week for evacuation, 15 - 90 mSv/month lot temporary relocation and 600 - 3,500 mSv/lifetime for permanent resettlement for intervention levels are also provided. The result can be applied as useful data to update intervention levels under the theoretical background in Korea.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
• /
• v.6 no.3
• /
• pp.15-23
• /
• 1995

The antenna height of the mobile communications lower than its typical surroundings causes multipath fading usually resulting in fast fluctuations of both signal strength and wave length in mobile radio communications. Therefore, there have been developed and used various wave be- havior prediction models, in some other foreign countries, based on the measurement data rather than on theoretical derivation. The main purpose of this paper is to examine the wave propagation characteristics particularly in Korean terrain with the measurements made in four types of different areas - a large city area, a small city area, a flat terrain area, and a mountain area. Those areas have been classified according to the terrain characteristics with which the particular area contains, such as scale and number of buildings, highways, trees, and so on. With the measured data of the field strength in the frequency band of pager system obtained from those four different areas, we compared the calculated ones from both Hata's and TIREM prediction models which are often applied in Korea.

• Smart Structures and Systems
• /
• v.15 no.1
• /
• pp.1-13
• /
• 2015

This paper proposes an analytical mode decomposition (AMD) and Hilbert transform method for structural nonlinearity quantification and damage detection under earthquake loads. The measured structural response is first decomposed into several intrinsic mode functions (IMF) using the proposed AMD method. Each IMF is an amplitude modulated-frequency modulated signal with narrow frequency bandwidth. Then, the instantaneous frequencies of the decomposed IMF can be defined with Hilbert transform. However, for a nonlinear structure, the defined instantaneous frequencies from the decomposed IMF are not equal to the instantaneous frequencies of the structure itself. The theoretical derivation in this paper indicates that the instantaneous frequency of the decomposed measured response includes a slowly-varying part which represents the instantaneous frequency of the structure and rapidly-varying part for a nonlinear structure subjected to earthquake excitations. To eliminate the rapidly-varying part effects, the instantaneous frequency is integrated over time duration. Then the degree of nonlinearity index, which represents the damage severity of structure, is defined based on the integrated instantaneous frequency in this paper. A one-story hysteretic nonlinear structure with various earthquake excitations are simulated as numerical examples and the degree of nonlinearity index is obtained. Finally, the degree of nonlinearity index is estimated from the experimental data of a seven-story building under four earthquake excitations. The index values for the building subjected to a low intensity earthquake excitation, two medium intensity earthquake excitations, and a large intensity earthquake excitation are calculated as 12.8%, 23.0%, 23.2%, and 39.5%, respectively.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.25 no.3
• /
• pp.239-250
• /
• 2022

In this paper, we analyze the performance of an FM radio based passive radar in the presence of deception jamming such as false-target generation. To do this, we examine the effects of applying the deception jamming signal to the passive radar through the derivation of the construction of the amplitude-range-Doppler(ARD) plot. The analysis results show that applying the deception jamming signal with the low power similar to the target echo signal generates false targets at positions set by the jamming variables compared to the real target position in the ARD plot. Also, it is possible to induce the jamming effect so that only false targets are detected by selecting appropriate jamming power. Simulations are included to verify the theoretical results and to discuss on the effectiveness of the deception jamming on the FM radio based passive radar.

• Structural Engineering and Mechanics
• /
• v.85 no.5
• /
• pp.679-691
• /
• 2023

Many codes allow designers to use the bending moment diagram computed by elastic analysis and modify it by a certain amount of moment redistribution (MR) to account for plastic behaviour of continuous beams. However, several researchers indicated that the MR at the ultimate limit state (𝛽_u) for some beams deviate significantly from the specified values of various codes. This paper examines the applicability of the provisions on 𝛽_u in ACI 318-19 and Eurocode 2 through numerical investigations and comprehensively explores the influencing factors. The results show that some parameters not considered in those codes influence 𝛽_u to a certain extent, where the ratio of tensile reinforcement ratio at intermediate support to tensile reinforcement ratio at midspan (𝜌_s1/𝜌_s2) and load type are crucial parameters to consider. The specific combination of these two parameters may make the codes overestimate or significantly underestimate the 𝛽_u. On the other hand, the yield state of both critical sections is found to have an important influence on the influence degree of each parameter on 𝛽_u. The yield conditions are investigated, and an empirical judgment equation is proposed. In addition, the influence laws of the critical parameters on 𝛽_u have been further proved by theoretical derivation. Finally, due to 𝜀_t is found to have a better linear correlation with 𝛽_u than x_u/d, equations as a function of 𝜀_t for predicting the 𝛽_u of continuous beams under the two loads are proposed, respectively.

• Structural Engineering and Mechanics
• /
• v.84 no.3
• /
• pp.375-391
• /
• 2022

This paper discussed and analyzed the interfacial stress distribution characteristic of adjacent cracks in Carbon Fiber Reinforced Polymer (CFRP) plate strengthened concrete slabs. One un-strengthened concrete test beam and four CFRP plate-strengthened concrete test beams were designed to carry out four-point flexural tests. The test data shows that the interfacial shear stress between the interface of CFRP plate and concrete can effectively reduce the crack shrinkage of the tensile concrete and reduces the width of crack. The maximum main crack flexural height in pure bending section of the strengthened specimen is smaller than that of the un-strengthened specimen, the CFRP plate improves the rigidity of specimens without brittle failure. The average ultimate bearing capacity of the CFRP-strengthened specimens was increased by 64.3% compared to that without CFRP-strengthen. This indicites that CFRP enhancement measures can effectively improve the ultimate bearing capacity and delay the occurrence of debonding damage. Based on the derivation of mechanical analysis model, the calculation formula of interfacial shear stress between adjacent cracks is proposed. The distributions characteristics of interfacial shear stress between certain crack widths were given. In the intermediate cracking region of pure bending sections, the length of the interfacial softening near the mid-span cracking position gradually increases as the load increases. The CFRP-concrete interface debonding capacity with the larger adjacent crack spacing is lower than that with the smaller adjacent crack spacing. The theoretical calculation results of interfacial bonding shear stress between adjacent cracks have good agreement with the experimental results. The interfacial debonding failure between adjacent cracks in the intermediate cracking region was mainly caused by the root of the main crack. The larger the spacing between adjacent cracks exists, the easier the interfacial debonding failure occurs.

• Journal of Aerospace System Engineering
• /
• v.18 no.2
• /
• pp.12-20
• /
• 2024

The application of reinforcement design to ensure the structural safety of electronics in small satellites is limited by the spatial constraints of the satellite structure during launch vibrations. Additionally, a reliable evaluation approach is needed for mounting highly integrated devices that are susceptible to fatigue failure. Although the Steinberg fatigue failure theory has been used to assess the structural integrity of electronic devices, recent studies have highlighted its theoretical limitations. In this paper, we propose a structural methodology based on the critical strain theory to design the digital control unit (DCU) of the X-band SAR payload component for the small SAR technology experimental project (S-STEP), a small satellite constellation. To validate the design, we conducted modal and random analyses using simplified modeling techniques. Based on our methodology, we ultimately demonstrated the structural safety of the electronics through analysis results, safety margin derivation, and functional tests conducted both before and after the launch test.