• Coupled systems mechanics
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• v.12 no.4
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• pp.391-407
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• 2023

This paper presents a static study of a rectangular functional graded material (FGM) plate, simply supported on its four edges, adopting a refined higher order theory that looks for, only,four unknowns,without taking into account any corrective factor of the deformation energy with the satisfaction of the zero shear stress conditions on the upper and lower faces of the plate. We will have determined the contribution of these stresses in the transverse deflection of the plate, as well as their effects on the axial stress within the interfaces between the layers(to avoid any problem of imperfections such as delamination) and on the top and bottom edges of the plate in order to take into account the fatigue phenomenon when choosing the distribution law of the properties used during the design of the plate. A numerical statement, in percentage, of the contribution of the shear effect is made in order to show the reliability of the adopted theory. We will also have demonstrated the need to add the shear effect when the aspect ratio is small or large. Code routines are programmed to obtain numerical results illustrating the validity of the model proposed in the theory compared to those available in the literature.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.29 no.2
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• pp.117-123
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• 1993

In order to analysis the tensile properties of the high-tech fibers for fishing gear materials. tensile strength was tested on raw materials, single yarns and netting twines(plied yarns)made of nylon, kevlar 29 and techmilon respectively. The results obtained are as follows: 1. The tensile stress and tenacity of unknotted single yarns in dry and wet conditions were 3 to 3.5 times greater in the high-tech fibers than in nylon. But the elongation of the high-tech fibers was about 15% of that in nylon. 2. The tensile strength of knotted single yarns in dry and wet conditions was arranged in order of as follows : techmilon. kelver 29, and nylon. The ratio of knot strength to tensile strength, knot efficiency, was the highest in nylon. 3. The tensile strength of unknotted netting twines in dry and wet conditions was 2.3 to 2.5 times greater in the high-tech fibers than in nylon. 4. The tensile strength of knotted netting twines in dry and wet conditions was arranged in order of as follows : techmilon, kevlar 29, nylon. The knot efficiency was the highest in nylon.

• Journal of Korean Association for Spatial Structures
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• v.22 no.4
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• pp.71-79
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• 2022

Recently, the construction of tall buildings utilized by high strength-concrete in the whole world is tending to be on the rise. The application of high-rise structural system in buildings results in the excellent cut-down effect in construction materials due to section reduction. Therefore, in order to investigate the CO₂ and resource reduction effect for the high-rise structural system, comparisons of GWP and ADP in embodied energy of structural materlais between 4 type of high-rise structural system have been performed. As a result, GWP emission increased in the order of steel structure outrigger system, RC shear wall system, and RC outrigger system. On the other hand, ADP emissions increased in the order of RC shear wall system, RC outrigger system, and steel structure outrigger system.

• The Journal of the Korea Contents Association
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• v.11 no.8
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• pp.475-487
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• 2011

In this paper, we present a systematic method to derive spectrum of high-order pulse and a novel design of e-Learning system that deals with deriving the spectrum using concept-based branching method. Spectrum of high-order pulse can be derived using conventional methods including 'Consecutive Differentiations' or 'Convolutions', however, their complexity of calculation should be too high to be used as the order of the pulse increase. We develop a recursive algorithm according to the order of pulse, and then derive the formula of spectrum connected to the order with a newly designed look-up table. Moving along, we design an e-Learning content for studying the procedure of deriving high-order pulse spectrum described above. In this authoring, we use the concept-based object branching method including conventional page or title-type branching in sequential playing. We design all four Content-pages divided into 'Modeling', 'Impulse Response and Transfer Function', 'Parameters' and 'Look-up Table' by these conceptual objects. And modules and sub-modules are constructed hierarchically as conceptual elements from the Content-pages. Students can easily approach to the core concepts of the analysis because of the effects of our new teaching method. We offer step-by-step processes of the e-Learning content through unit-based branching scheme for difficult modules and sub-modules in our system. In addition we can offer repetitive learning processes for necessary block of given learning objects. Moreover, this method of constructing content will be considered as an advanced effectiveness of content itself.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.1
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• pp.12-17
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• 2018

In order to enhance the realism of a virtual environment, a method of maximizing the stiffness of the virtual environment model is needed, which maintains the stability of the haptic system. In our previous research, we proposed a haptic system with a first order hold, instead of a zero order hold, and showed that the maximum available stiffness of a virtual spring with the first-order hold is larger than that with the zero-order hold. However, in terms of real system implementation, the zero order hold is a more common and easy method. In this paper, we propose an extrapolation method and a high frequency zero-order-hold output method in order to obtain the stability region using a zero order hold, which is equivalent to the method using the first-order-hold. The simulation results shows that the stability range of the virtual spring becomes almost the same as that of the method using the first order hold when the sampling period of the high frequency zero-order-hold method is decreased. Moreover, the stability range of the proposed method is several times to several tens of times greater than that of the method using the zero order hold only. Therefore, it is expected that the proposed method can enhance the realism of rigid bodies in a virtual environment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.2C
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• pp.191-199
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• 2006

In this paper, we propose a method to implement a predistorter of the $rho$-th order inverse filter structure to prevent signal distortion and spectral re-growth due to the high PAPR (peak-to-average ratio) of the OFDM signals and the non-linearity of high-power amplifiers. We model the memory-less non-linearity of the high-power amplifier with a polynomial model and utilize the inverse of the model, the $rho$-th order inverse filter, for the predistorter. Once the non-linearity is modeled with a polynomial, since we can determine the $rho$-th order inverse filter only with the coefficients of the polynomial, large memory is not required. To update the coefficients of the non-linear high-power amplifier model, we can use LMS or RLS algorithms. The convergence speed is high since the number of coefficients is small, and the computation is simple since manipulation of complex numbers is not necessary.

• 전기의세계
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• v.24 no.5
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• pp.67-71
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• 1975

A dynamic stability analysis of a large interconnected power system takes much time even though the modern large computer is used because of the high order of the system dynamic equations. By the necessity of the low order power system models, a simplified power system model of the generator with the high speed solid state exciter is developed in this paper. The usefulness of the reduced model is confirmed by comparing its eigenvalues and the transient responses with those of the original model in the single machine to infinite bus power system.

• Wind and Structures
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• v.31 no.5
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• pp.473-482
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• 2020

The first-order method for estimating the extreme wind pressure on building envelopes with consideration of the directionality of wind speed and wind pressure is improved to enhance its computational efficiency. In this improved method, the result is obtained directly from the empirical distribution of a random selection of annual maximum wind pressure samples generated by a Monte Carlo method, rather than from the previously utilized extreme wind pressure probability distribution. A discussion of the relationship between the first- and full-order methods indicates that when extreme wind pressures in a non-typhoon climate with a high return period are estimated with consideration of directionality, using the relatively simple first-order method instead of the computationally intensive full-order method is reasonable. The validation of this reasonableness is equivalent to validating two assumptions to improve its computational efficiency: 1) The result obtained by the full-order method is conservative when the extreme wind pressure events among different sectors are independent. 2) The result obtained by the first-order method for a high return period is not significantly affected when the extreme wind speeds among the different sectors are assumed to be independent. These two assumptions are validated by examples in different regions and theoretical derivation.

• Journal of Fisheries and Marine Sciences Education
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• v.18 no.2
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• pp.122-136
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• 2006

The purpose of this study is to explore the features and features of causes of communicative deficits in high-functioning autistic children in order to intervene educational programs. When communicating with others, high-functioning autistic children have difficulties in the aspects of syntax and semantics, especially pragmatics. These causes of communicative deficits of high-functioning autistic children can be explained respectively by theory of mind, executive function, and central coherence theory. According to theory of mind, qualitative impairment of interaction and communication accounts for communicative deficits. Executive function argues that communicative deficits of high-functioning autistic children be caused by limited concern. Central coherence theory suggests that communicative deficits be caused by the inappropriate integration of cues. Considering these causes of communicative deficits in high-functioning autistic children, we proposed educational strategies order to intervene educational programs.

• Corrosion Science and Technology
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• v.7 no.1
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• pp.61-67
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• 2008

In this paper, electrochemical and microstructural characteristics of nickel-plated Alloy 600 were investigated in order to identify the performance of electroless Ni-plating on Alloy 600 in high-temperature aqueous condition with the comparison of electrolytic nickel-plating. For high temperature corrosion test of nickel-plated Alloy 600, specimens were exposed for 770 hours to typical PWR primary water condition. During the test, open circuit potentials (OCP's) of all specimens were measured using a reference electrode. Also, resistance to flow accelerated corrosion (FAC) test was examined in order to check the durability of plated layers in high-velocity flow environment at high temperature. After exposures to high flow rate aqueous condition, the integrity of surfaces was confirmed by using both scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). For the field application, a remote process for electroless nickel-plating was demonstrated using a plate specimen with narrow gap on a laboratory scale. Finally, a practical seal design was suggested for more convenient application.