• ETRI Journal
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• 제21권1호
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• pp.1-27
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• 1999

We present a new description of envelope-function equation of the superlattice (SL). The SL wave function and corresponding effective-mass equation are formulated in terms of a linear combination of Bloch states of the constituent material with smaller band gap. In this envelope-function formalism, we review the fundamental concept on the motion of a wave packet in the SL structure subjected to steady and uniform electric fields F. The review confirms that the average of SL crystal momentums K = ($k_x,k_y,q$), where ($K_x,k_y$) are bulk inplane wave vectors and q SL wave vector, included in a wave packet satisfies the equation of motion = $_0+Ft/h$; and that the velocity and acceleration theorems provide the same type of group velocity and definition of the effective mass tensor, respectively, as in the Bulk. Finally, Schlosser and Marcus's method for the band theory of metals has been by Altarelli to include the interface-matching condition in the variational calculation for the SL structure in the multi-band envelope-function approximation. We re-examine this procedure more thoroughly and present variational equations in both general and reduced forms for SLs, which agrees in form with the proposed envelope-function formalism. As an illustration of the application of the present work and also for a brief investigation of effects of band-parameter difference on the subband energy structure, we calculate by the proposed variational method energies of non-strained $GaAs/Al_{0.32}Ga_{0.68}As$ and strained $In_{0.63}Ga_{0.37}As/In_{0.73}Ga_{0.27}As_{0.58}P_{0.42}SLs$ with well/barrier widths of $60{\AA}/500{\AA}$ and 30${\AA}/30{\AA}$, respectively.

• Journal of The Korean Association of Information Education
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• 제23권6호
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• pp.655-663
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• 2019

Recent interest in software education has naturally led to interest in computer science. Computer science is the study of theory and principle of computer and computational systems. This knowledge and concept of computer science is fundamental to software education. Recently, "Computer Science (CS) Unplugged", which is an educational method for introducing students to concepts of computer science without using a computer, has been widely used in classes around the world. CS Unplugged is a method for learning the basic principles of computer science through diverse playing activities. The problem, however, is that these CS unplugged activities take place in class without an analysis of how closely they relate to the core subjects learned in real computer science. Therefore, in this study, we will study on the comparison between the core contents of computer science and the core contents of computer science contained in the various activities of CS Unplugged.

• Journal of Digital Convergence
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• 제9권3호
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• pp.47-58
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• 2011

As China's international status is more and more uplifted, the active shaping and effective propagation of China's national image has been regarded as an important means to demonstrate China's soft power, demolish the so-called "China Threat Theory", and compete for China's share in international discourse power. This article first makes a discussion on the fundamental concepts and related theories of national image, and then explores the precise positioning of China's image as "a responsible power" and the connotation that should be contained in this image. Finally, this article presents a tactic of "complex propagation" for the shaping of China's national image, which includes the propagation by new media and advertisement, the marketing of international sport games and other international events, public diplomacy and public relations tactics.

• Geotechnical Engineering
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• 제13권1호
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• pp.5-18
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• 1997

In order to make reliable ground shock predictions in saturated geological media, it is necessary to use multi -phase material models and numerical codes. This paper presents the results of theoretical study of the fundamental behavior of multi-phase porous media subjected to high dynanlic loadings, and deals with the development of numerical code MPDAP with JWL(Jones-Wilkins-Lee) model, which is capable of considering the kinds and characters of explosives. To check the global equilhorium equations of the numerical code, we carried out some verifications. In the cases of the elastic spherical wave propagation in a single phase medium, one-dimensional linear ronsolidation, and one timensional wave propagation in saturated linear elastic soils and rocks, the results calculated by MPDAP show close agreement with closed-form solutions or numerical solutions generated with two phase code.

• The Journal of Korean Institute of Communications and Information Sciences
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• 제33권5A호
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• pp.526-535
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• 2008

Recently, several MAC protocols using the directional antennas have been proposed for wireless mobile ad hoc networks. In the theory, it can improve spatial reuse and communication throughput in the Mobile Ad-hoc networks. But, or However even though direction transmissions using the Directional MAC protocol(D-MAC) are expected to provide significant improvements, they causes other problems such as deafness problem and fairness problem. In this paper, we analyze the D-MAC protocol in Mobile Ad-hoc network for Vehicle to vehicle(V2V) communication. Through the results of the analysis, We the fundamental problem of D-MAC protocol and finally we suggest new D-MAC protocol for V2V networks.

• Journal of Navigation and Port Research
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• 제35권5호
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• pp.371-380
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• 2011

Traditionally, UNCLOS stipulates that States have the obligation and responsibility to protect and preserve the marine environment and exercise their rights in Principle of Non-Discrimination with respect to foreign ships visiting to port states. UNFCCC and Kyoto protocol established Common but Differentiated Responsibility as the basis which is established on the historic responsibility. The principle in which IMO is presently developing the regulations of Green House Gas emitted from ships is contradict with the principle of UNFCCC regime. In this paper, the development and the principle of UNFCCC and Kyoto protocol is surveyed and it provides the tendency of the IMO activities regarding GHG emission from ships. Also, through consideration of the problems and restrictions drawn from comparison between two principles, the conclusion suggests the fundamental theory and implementation means in order to carry out the purpose of IMO regulations in accordance with the principles of UNCLOS and IMO Convention.

• The Transactions of the Korean Institute of Power Electronics
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• 제8권6호
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• pp.576-584
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• 2003

This paper presents a new control method of single-phase active power filter(APF) for the compensation of harmonic current components in nonlinear loads. Constructing a imaginary second-phase giving time delay to load currents, making single-phase system into the system that has two phases, complex calculation is possible. In the previous method, it made a imaginary-phase lagged to the load current T/4(here T is the fundamental cycle), but in proposed method, the new signal, which has the delayed phase through the filter, using the phase-delay property of low-pass filter, was used to the second phase. Instantaneous calculation of harmonic current is possible, because two phase have different phase. In this paper, it was done with instantaneous calculation using the rotating reference frames(RRF) that synchronizes with source-frequency, a reference of compensation currents, not applying to instantaneous reactive power theory which uses the existed fixed reference frames. The simulation and experiment about R-L loads using the current source were carried out, and the effect of the proposed method was preyed through the result of this experiment.

• Journal of the Korean Society of Clothing and Textiles
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• 제35권11호
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• pp.1399-1408
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• 2011

This study analyzes the current educational curricula in the field of clothing construction to provide some fundamental information for developing more appropriate educational courses and to activate the fashion business. A total of 82 different departments related to fashion and apparel were selected from four-year domestic universities and the curricula recently posted on their internet websites were analyzed by descriptive statistics. More than half (53.7%) of the 82 departments were offering classes in the clothing construction field for 3 credits and 4 class hours. College affiliation of the departments that offered curricula in the clothing construction field was classified into 5 categories: the arts (34), human ecology (22), natural sciences (14), humanities/culture (9), and others (3). Human ecology category showed the highest results in the average class hours (3.9), the number of classes in the clothing construction field (7.6), and the percentage of the classes in the clothing construction field out of all major classes offered by the clothing department (19.9%). All 82 departments were classified into 3 categories of: fashion design (32), clothing (28), and fashion business (22). The clothing category showed the highest results in the average credits (2.8), class hours (3.8), the number of classes offered by the clothing construction field (7.6), and the percentage of the classes that offer clothing construction education out of all major classes offered by the clothing department (19.9%). The educational contents of clothing construction area were classified into 8 different categories of: basic theory and sewing, clothing construction, flat pattern, draping, tailoring and advanced clothing construction, pattern CAD, sewing science and apparel manufacturing process, and clothing construction for special needs. Among these categories, the draping category constituted 21.7% as the largest part. In addition, the distribution of classes offered by 4 academic years were analyzed into 8 different categories.

• Journal of the Korean Society of Clothing and Textiles
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• 제40권6호
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• pp.1085-1099
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• 2016

This article is designed to establish fundamental design criterion for theme park cast costumes in accordance with play type and space. There is an understanding that theme parks act as a play space that is designed to meet diverse playing desires. To analyze cast costumes, the theme park - 'Everland' in South Korea as an example, area was divided into attraction space and non-attraction space. Attraction space is mainly for full-scale play content areas and the non-attraction space is to enforce the attraction space experience. Roger Caillois's play theory states that there are 4 play types; Illinx, Mimicry, $Ag{\hat{o}}n$, and Alea. All 4 play types were shown through attraction and Mimicry at non-attraction. Each cast costume was analyzed in terms of apparel design elements - silhouette, textile, color, detail, and props - related to play type facility and cast role. Criteria for theme park cast costume designs were suggested based on the results. Illinx cast members who fulfill a safety-checking role wear high chroma warm color costumes with the accent on details in bodice cutting lines, collar edges, pockets, buttons and decorative ornaments. A complementary contrast is also used. The guidance cast in Illinx may wear a suit in bright/vivid color. Mimicry guidance cast costumes show meticulous perfection in imitation with the figure in its space. From head to toe, color, textile, and silhouette - every detail and even props should match the character. $Ag{\hat{o}}n$ cast costumes are strictly limited in detail and decorative ornament usage as well as in color, since they are in charge of the management and operation of a competition. Alea cast's role is a self-demonstrator. Alea cast members should be a real tarot card reader. However, a manual should control their costumes. A total of 10 cast roles at a non-attraction space should be designed to show job patterns clearly in accordance with the whole theme at the park.

• Transactions of the Korean Society of Automotive Engineers
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• 제2권6호
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• pp.94-101
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• 1994

About vibration model of Six-degrees-of-freedom(DOF), in mass load, examined results for knowing dynamic interference and response variation is as follows; In case of putting mass load upon the object, experimented results on two-degrees-of-freedom of the translation-1 direction and the rotation-1 direction at open-loop-control system, about 0.19 arcsed in input of the translation-$0.1{\mu}m$ and $0.022{\mu}m$ on input of the rotation-0.5 arcsec, the justicse of motion equation is acknowledged as confirming the appearance of the interference-$0.022{\mu}m$. In establishing calculation of transformation matrix by using analogue circuit, as simulating results that used incomplete differentiation, interference is $1.7{\times}10^{-3}$ arcsec on input of the translation-$0.1{\mu}m$ and $1.4{\times}10^{4}{\mu}m$ on input of the rotation-0.5 arcsec in open-loop-control system. Also it is $4.2{\times}10^{-4}$ arcsec on input of the translation-$0.1{\mu}m$ and $5.6{\times}10^{-5}{\mu}m$ on input of the rotation-0.5 arcesc in closed-loop-control system. As closed-loop-control system is better than open-loop-control system, equivalent accordance is confirmed on original response. Finally, fundamental validity of this theory is acknowledged.