• Journal of the Korean Magnetics Society
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• v.2 no.3
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• pp.222-227
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• 1992

The effects of $V_2O_5$ addition as an additive on the densification, the microstructure and the magnetic properties of Mn-Zn ferrites were studied. The maximum density was observed at 0.1 wt% $V_2O_5$ content and it was recognized that a small content of $V_2O_5$ prohibited the discontinuous grain growth. The initial permeability showed maximum at 0.1 wt% $V_2O_5$ content and the power loss minimum at 0.03 wt% $V_2O_5$ content. It was found that a small content of $V_2O_5$ went into solid solution in the Mn-Zn ferrites, but above that extent $V_2O_5$ formed a second phase to be segregated at the grain boundaries.

• Applied Microscopy
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• v.12 no.1
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• pp.11-21
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• 1982

A number of recent ultrastructural studies have shown marked differences between the two lining cell types in adult liver sinusoids, endothelial cells and Kupffer cells. In the present study, the ultrastructural features and electron microscopic cytochemistry of sinusoidal lining cells in the fetal liver were studied through fetal period to neonate in the rat. At fetal period, the sinusoid, which contains various blood component, in lined by the endothelial cells, the Kupffer cells and the fat storing cells that located in the space of Disse. As gestation proceeded, these eel's are arranged as adult liver sinusoids. The sinusoidal wall appears to be discontinuous with open fenestration between endothelial cells, but no basal lamina can observed. It seems to be morphologically and functionally distinct at the early gestation between the endothelial cells and the Kupffer cells, the latter showing marked phagocytized activity. The fat storing cells, which contain several fat droplets, are located in the space of Disse. Ultrastructural localization of the acid and alkaline phosphatase activity were noted on the sinusoidal lining cells.

• Journal of the Korean Society of Costume
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• v.62 no.5
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• pp.1-15
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• 2012

In a fast changing postmodern society, contemporary fashion is becoming more complicated and ambiguous along with other genres of art than ever before. This phenomenon reigning as a sociocultural paradigm can be defined as 'indeterminacy' and it means 'undecidability'. The purpose of this study is to clarify and analyze the indeterminate characteristics of contemporary fashion reviewing the theoretical background and the architectural formativeness as a comparative research. The core idea of deconstructivism dismantles a causal relationship between function and form in fashion and the conventional notion about clothes. Complexity theory, which is the study of chaotic dynamical systems, suggests the creative idea and concept of infinite possibilities on a formative method. Meanwhile, catastrophe theory of discontinuous change can be used as interpretative strategies for the process of deconstruction and reconstruction. As a result of this study, the indeterminacy of fashion can be analyzed into five semantic categories: irregularity, immateriality, randomness, complexity and changeability. The intrinsic value of the indeterminacy in contemporary fashion is the interaction with a sociocultural ideology and a technological environment as well as an expansion of formative expression. To conclude, it can be said that the indeterminacy in fashion is a new interpretation of the relationship among body and space, clothes and society.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.4
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• pp.510-516
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• 2013

This paper suggests a 3-phase series-resonant type high voltage capacitor charger for an EML pulsed power system. The operating principle on the charger is explained by an equivalent circuit. Additionally, we analyze the charging characteristic in one discontinuous conduction mode and three continuous conduction modes. The analysis shows that the resonant current per phase is two thirds of the 3-phase charger's average charging current and one third of the single-phase charger's average charging current with the same capacity. We suggest a design method of the 3-phase capacitor charger in each operational mode and present an example of 3.5 kW capacitor charger at ${\omega}_s=0.33{\omega}_r$. The 3.5 kW 3-phase capacitor charger prototype is assembled with a TI28335 controller and a 40 kJ, 7 kV capacitor. The design rules based on the analysis are verified by experiment.

• Journal of Power Electronics
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• v.13 no.2
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• pp.232-242
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• 2013

To obtain phase currents information in AC drives, shunt sensing technology is known to show great performance in cost-effectiveness and therefore it is widely used in low cost applications. However, shunt sensing methods are unable to acquire phase currents in certain operation conditions. This paper deals with the derivation of the boundary conditions for phase current reconstruction in three-shunt sensing inverters and proposes a voltage injection method to expand the measurable areas. As the boundary conditions are deeply dependent on the switching patterns, they are typically analyzed on the voltage vector plane for space vector pulse width modulation (SVPWM) and discontinuous pulse width modulation (DPWM). In the proposed method, the voltage injection and its compensation are conducted within one sampling period. This guarantees fast current reconstruction and the injected voltage is decided so as to minimize the current ripple. In addition to the voltage injection method, a sampling point shifting method is also introduced to improve the boundary conditions. Simulation and experimental results are presented to verify the boundary condition derivation and the effectiveness of the proposed voltage injection method.

• Interaction and multiscale mechanics
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• v.4 no.4
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• pp.291-311
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• 2011

To simulate the self excited torsional vibrations of rotating drill strings (DSs) in vertical bore-holes, the nonlinear wave models of homogeneous and sectional torsional pendulums are formulated. The stated problem is shown to be of singularly perturbed type because the coefficient appearing before the second derivative of the constitutive nonlinear differential equation is small. The diapasons ${\omega}_b\leq{\omega}\leq{\omega}_l$ of angular velocity ${\omega}$ of the DS rotation are found, where the torsional auto-oscillations (of limit cycles) of the DS bit are generated. The variation of the limit cycle states, i.e. birth (${\omega}={\omega}_b$), evolution (${\omega}_b<{\omega}<{\omega}_l$) and loss (${\omega}={\omega}_l$), with the increase in angular velocity ${\omega}$ is analyzed. It is observed that firstly, at birth state of bifurcation of the limit cycle, the auto-oscillation generated proceeds in the regime of fast and slow motions (multiscale motion) with very small amplitude and it has a relaxation mode with nearly discontinuous angular velocities of elastic twisting. The vibration amplitude increases as ${\omega}$ increases, and then it decreases as ${\omega}$ approaches ${\omega}_l$. Sectional drill strings are also considered, and the conditions of the solution at the point of the upper and lower section joints are deduced. Besides, the peculiarities of the auto-oscillations of the sectional DSs are discussed.

• Asian-Australasian Journal of Animal Sciences
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• v.12 no.5
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• pp.702-707
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• 1999

A percoll density gradient technique was developed for producing high quality turkey semen and improving the fertility by removing deleterious cellular components, including spermiophages, bacteria, abnormal or dead spermatozoa, and other cellular debris. The combination of three different percoll densities, 1.05, 1.07, and 1.08 showed the best resolution and was selected to prepare a discontinuous percoll density gradient to obtain healthy spermatozoa from semen smples. Bacteria, spermiophages, and abnormal or dead spermatozoa were detected from the density range from 1.05, 1.05 to 1.07, and 1.07 to 1.08, respectively. Healthy spermatozoa were collected from the density greater than 1.08. Spermatozoa obtained from percoll density gradient centrifugation showed better sperm motility than those from unprocessed pooled semen. Bacteria including Escherichia coli, Staphylococcus aureus, and Proteus spp., were predominant contaminants in turkey semen, and the numbers of cells were approximately $5{\times}10^5$ to $1{\times}10^9cfu/ml$. The overall fertility rates in hens inseminated with processed percoll density gradient were higher than those in hens with unprocessed semen especially for unhealthy sperm. In conclusion, semen quality can be improved by percoll density gradient centrifugation, which augmented the fertility of turkey breeders.

• Korean Institute of Interior Design Journal
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• v.20 no.6
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• pp.88-96
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• 2011

In contemporary urban space, the identify is absent because of the object-oriented plans that ignore the context of urban space, and the ignorance of the regional characteristics and the historicity of places. Due to this reason, urban space lost its unique characteristics and becomes a mismatch with its surroundings. To solve these problems, the ideological trend of post-modernism emerged and new spatial paradigm rose based on the contextual concept to go with this trend. This contextual concept should be considered more importantly in the public space with discontinuous many and unspecified behavioral patterns. The components of space do not exist independently with individual identity. They should be considered based on a holistic view formed by the relations among elements and the establishment of those relations, and through this, correct identity can be established. Thus, this paper aims to analyze the context of spatial components through new contextual views on public spaces and study the expressional characteristics unveiled between these relations.

• Korean Institute of Interior Design Journal
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• v.20 no.6
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• pp.236-243
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• 2011

The digital space color of new media environment denied not only the deterministic relationship of designed color and circumjacent color but also the deduced an special elements of digital space color. Such phenomena historical perspective of Gernot Wersig, new media principle of Lev Manovich and remediation of Bolter, J.K & Grusin, R. are expressed in various new media environment across. In particular, development of digital technology is moving away from its previous space color based on scientific, statistical and quantitative perspective by using diverse variables. The following research focuses on the fundamental concept of space color by type, composition of digital space color. The paper reflects on the meaning and concept of contemporary which enables the application of digital space color system on space through advanced technology. The principle of digital space color such as multidimensional malerisch, discontinuous video, vague original and copy, irregular repetitiveness of 'copy of copy', selective color of observer, experiential color of observer, and etc. makes it possible to extract the expressed element and method of digital space color. Meanwhile, the features of digital space color such as divided field of form, non-systematized of process and collage of communication can be inferred from case analysis.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.3
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• pp.275-281
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• 2011

When a flat bar type metal specimen for general tension test is subject to incremental uniaxial tension, a narrow plastic shear band, so called luders band, is generated at some instance. This band typically has an angle to the axis of specimen and many early researches have been done to investigate the condition and angle of this localized deformation phenomenon by many researchers. This study follows the procedure of Thomas(1961) under plane stress boundary condition. $J_2$ plasticity theory, balance of linear momentum, and constitutive equations are used to derive the angle of luders band under plain strain boundary condition. The result was confirmed by other angle based on acoustic tensor theory.