• Journal of Power Electronics
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• 제8권1호
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• pp.91-100
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• 2008

The d-q harmonic detecting algorithms are dominant methods to generate current references for active power filters (APF). They are often implemented in the synchronous frame and time domain. This paper researches the frequency characteristics of d-q synchronous transformations, which are closely related to the analysis and design issues of control system. Intuitively, the synchronous transformation is explained with amplitude modulation (AM) in this paper. Then, the synchronous filter is proven to be a time-invariant and linear system, and its transfer function matrix is derived in the stationary frames. These frequency-domain models imply that the synchronous transformation has an equivalent effect of frequency transformation. It is because of this feature, the d-q method achieves band-pass characteristics with the low pass filters in the synchronous frame at run time. To simplify these analytical models, an instantaneous positive-negative sequence frame is proposed as expansion of traditional symmetrical components theory. Furthermore, the synchronous filter is compared with the traditional bind-pass filters based on these frequency-domain analytical models. The d-q harmonic detection methods are also improved to eliminate the inherent coupling effect of synchronous transformation. Typical examples are given to verify previous analysis and comparison. Simulation and experimental results are also provided for verification.

• 한국환경성돌연변이발암원학회지
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• 제16권1호
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• pp.35-42
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• 1996

Aragonite is one of polymorphs of calcium carbonate of which main form is calcite. We found that white precipitate is formed in much amount by boiling underwater of Inchon, Korea and confirmed that it is aragonite. This study is to evaluate the dimensional characteristics, solubility, acid resistance of aragonite and the cytotoxicity, cell division disturbance and cell transforming ability of it on BALB/3T3 cells. The results are as follows: Lengths of the aragonite were reduced to the 72.7% and 22.7% respectively after 5 months and 7 months of intrapleurai injection to the Sprague-Dawley rat. Strong acid such as 1M HCl dissolved the aragonite instantly but weaker acid pH 2.0 or more could not dissolved aragonite easily. The result of cell growth inhibition showed that cell numbers were decreased as log-doses of treatment of the aragonite were increased 24 hours, 48 hours, and 72 hours later. Cell plating efficiency after the aragonite treatment also showed dose-dependent decrease. Multinuclear giant cell formation was increased in the aragonite treated cells until ID$_{50}$ and after the dose the multinucleate cells were decreased, but remained much higher than negative control cells. Morphological transformation assay showed that the aragonite did not induce transformation in all treated doses.

• Journal of Welding and Joining
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• 제25권3호
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• pp.78-84
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• 2007

Laser Material Processing has been replaced the conventional machining systems - cutting, drilling, welding and surface modification and so on. Especially, LTH(Laser Transformation Hardening) process is one branch of the laser surface modification process. Conventionally, some techniques like a gas carburizing and nitriding as well as induction and torch heating have been used to harden the carbon steels. But these methods not only request post-machining resulted from a deformation but also have complex processing procedures. Besides, LTH process has some merits as : 1. It is easy to control the case depth because of output(laser power) adjustability. 2. It is able to harden the localized and complicated a.ea and minimize a deformation due to a unique property of a localized heat source. 3. An additional cooling medium is not required due to self quenching. 4. A prominent hardening results can be obtained. This study is related to the surface hardening of the rod-shaped carbon steel applied to the lathe based complex processing mechanism, a basic behavior of surface hardening, hardness distribution and structural characteristics in the hardened zone.

• 한국주거학회논문집
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• 제22권3호
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• pp.123-134
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• 2011

'Sohawjang' is the first apartment house built in Busan the modern period, 1944. 'Sohawjang' needs to be apprised its value as an very important object of study with architectural and dwelling historic meaning because multi-family houses built in Japanese Rule Era that now exist in Korea are very rare. Thus, this study attempted to leave records to archive by conducting face to face interviews and surveying on 'Sohawjang' which is seriously in danger of extinction and its original form damage as the first step. Especially, around Korea's Liberation, this study tried to extract transformation characteristics of residential space and cultural differences appeared on differences of occupants having different nationality. Through these results, this study attempted to examine the era of apartment house and transformation characteristics and values of modern dwelling historic dimension according to changes of users appeared in Busan modern period. Through this study, it offers basic data about introduction and transition processes of an apartment house in Korea. It has an meaning of suggestion reference data for original form preservations or regenerations.

• 한국조경학회지
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• 제23권1호
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• pp.157-173
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• 1995

Seowons were first established during the Koryo Dynasty and contain primate shrines for the service of ancestors and ancient sages. Seowons were located in a scenic or rural place some distance from a residential area. The direct motive for building the Seowon came from the need for transcendental concealment and evasive retirement which developed as a result of oppression of scholars The indirect motivations were the development of loaming in an idyllic natural settings and the creation of a beautiful natural environment. he purpose of tai study is to investigate the characteristics and transformation process of the location of Seowon in the Chosen dynasty. The results of this research are summarized as fellows : 1. Seowons were in hilly areas with good geographical features including a nice view of the mountains and waters. Beowons were also built on the relation place of an ancient sage and of destroyed Buddist temples. 2. The location patterns of seowon in the Choson dynasty underwent three stages with the change of time Political and social phenomena influenced the transformation of the location patterns Research in this area is at an early stage. The present study was confined to an examination of 7he characteristics and transformation process of the location of seowons. However, it is hoped that this study will offer meaningful guide for further research.

• 한국산업정보학회논문지
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• 제4권3호
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• pp.90-94
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• 1999

디지틀 의사 랜덤변환의 출력이 같은 랜덤성을 갖는 것을 방지하기 위해서 카오스적인 처리과정이라 부르는 보다 랜덤하고, 결정론적인 변환과정을 소개하였다. 카오스적인 변환과정을 거치면, 카오스적인 랜덤순서가 발생하는 데, 이 카오스 변환은 결정론적 카오스함수를 기본으로 설계하였으며, 쉬프트 레지스터와 같은 간단한 하드웨어로 구현할 수 있었다. 본 논문에서는 쉬프트 레지스터로 구현한 카오스변환 회로를 제시하였고, 제시한 회로의 카오스적인 거동은 카오스 거동을 갖는 톱니함수 특성으로 설명하였다.

• 대한가정학회지
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• 제44권12호
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• pp.167-178
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• 2006

The purpose of this study is to analyze the transformed fashion design based on the principles of visual design. Wucius Wong classified the kinds of transformation techniques as internal variation, external variation, extension, superimposition, transfiguration, dislocation, and distortion, which create and modify the shape. And the kinds of shape grammar for transformation are rule deletion, rule addition, and rule transformation, which are applied to interpretate for the change of wearing, the specialization & development of clothes, and the avant-garde styles in subculture groups. The formative meanings of the transformed fashion design are multi-transformation with complexity, formal beauty pretending confusion, and the basis for new trend.

• 한국실천공학교육학회논문지
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• 제2권2호
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• pp.36-41
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• 2010

푸리에 변환과 관련하여 많은 참고할 수 있는 문헌이 존재하지만, 수식의 복잡성과 차이로 인해, 초보자가 푸리에 변환을 이해하고 활용하는 데에는 어려움이 따른다. 본 논문에서는 관련된 수식을 정리하고 수치 결과의 비교를 통하여 푸리에 변화을 이해하고자 하였다. 대표적인 입력신호에 대하여 푸리에 변환 결과를 도시하였고 푸리에 변환의 특성을 정리하였다.

• 한국주조공학회지
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• 제28권1호
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• pp.31-36
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• 2008

Ti-Ni-Cu alloys are very attractive shape memory alloys for applications as actuators because of a large transformation elongation and a small transformation hysteresis. Rapidly solidified Ti-Ni alloy ribbons have been known to have the shape memory effect and superelasticity superior to the alloy ingots fabricated by conventional casting. In this study, solidification structures and shape memory characteristics of $Ti-Ni_{30}-Cu_{20}$ alloy ribbons prepared by melt spinning were investigated by means of DSC and XRD. Operating parameters to fabricate the amorphous ribbons were the wheel velocity of 55 m/s and the melt spinning temperature of $1500^{\circ}C$. The crystallization temperature was measured to be $440^{\circ}C$. The crystallized ribbons exhibited very fine microstructure after annealing at $440^{\circ}C$ for 10 minutes and $460^{\circ}C$ for 5 minutes and was deformed up to about 6.8% and 6.23% in ductile manner, respectively. Stress-strain curve of the ribbon exhibited a flat stress-plateau at 64 MPa and this is associated with the stress-induced a B2-B19 martensitic transformation. During cycle deformation with the applied stress of 220 MPa, transformation hysteresis and elongation associated with the B2-B19 transformation were observed to be $4.3^{\circ}C$ and 3.6%.

• Journal of Advanced Marine Engineering and Technology
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• 제31권8호
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• pp.961-969
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• 2007

The laser material processing has replaced a conventional material processing such as a welding, cutting, drilling and surface modification and so on. LTH(Laser Transformation Hardening) is one branch of the laser surface modification process. A lot of energy is needed for the LTH process to elevate workpiece surface to temperature of the austenite transformation($A_3$), which results from utilizing a beam with a larger size and lower power intensity comparatively. The absorptivity of the laser energy with respect to material depends on the wave length of a beam. This study is related to the surface hardening for the rod-shaped carbon steel by the high power diode laser(HPDL) whose beam absorptivity is better than conventional types of lasers such as $CO_2$ or Nd:YAG laser. Because a beam proceeds on the rotating specimen the pretreated hardened-phase can be tempered and softened by the overlapping between hardened tracks. Accordingly, the longitudinal hardness measurement and observation of the micro structure was carried out for an assessment of the hardening characteristics. In addition, a hardening characteristics as a hardenability of materials was compared in the point of view of the hardness distribution and hardening depth and width.