• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.5
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• pp.483-490
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• 2008

Minimization of nozzle induces many flow losses in micro-propulsion system. In this study, we studied about thermal transpiration based micro propulsion system to overcome these losses. Thermal transpiration device(Knudsen pump) having no moving parts can self-pump the gaseous propellant by temperature gradient only (cold to hot). We designed, fabricated the Knudsen pump and analyzed pressure gradient efficiency of membrane according to Knudsen number under vacuum condition. Experimental results showed that thick membranes are more effective than thin membranes in transition flow regime, and pressure gradient efficiency according to Knudsen number is increased to maximum 82% apart from membrane thickness in free molecular regime.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1997.11a
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• pp.98-103
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• 1997

Defuzzification plays a great role in fuzzy control system. Defuzzification is a process which maps from a space defined over an output universe of discourse into a space of nonfuzzy(crisp) number. But, it's impossible to convert a fuzzy set into a numeric value without losing some information during defuzzification. Also it's very hard to find a number that best represents a fuzzy set. Many methods have been used for defuzzification but most of then were problem dependent. There has been no rule which guides how to select a method that is suitable to solve given problem. Here, we have investigated most widely used methods and we have analyzed their characteristics and evaluated them. D. Driankov and Mizumoto have suggested 5 criteria which the‘ideal’defuzzification method should satisfy. But, they didn't considered about control action. Output fuzzy set if not only a fuzzy set but also a sequence of control action. We suggested 4 new criteria which describe sequence of cont ol action from some experiments. In addition, we have compared each method in simple adaptive fuzzy control. COG(Center of Gravity), or COS(Center of Sums) methods were successful in fuzzy control. However, at transition region, MOM(Mean of Maxima) was best among others in adaptive fuzzy control.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.140.2-140.2
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• 2012

The silicate carbon star IRAS 09425-6040 shows very conspicuous crystalline silicate dust features and excessive emission at far infrared. To investigate properties of dusty envelopes around the object, we use radiative transfer models for axisymmetric and sphericallly symmetric dust distributions. We perform model calculations for various possible combinations of dust shells and disks with various dust species. We compare the model results with the observed spectral energy distributions (SEDs) including the IRAS, ISO, AKARI, MSX and 2MASS data. We find that a model with multiple disks of amorphous and crystalline silicate and multiple spherical shells of carbon dust can reproduce the observed SED fairly well. This supports the scenario for the origin of silicate carbon stars that oxygen-rich material was shed by mass loss when the primary star was an M giant and the O-rich material is stored in a circumbinary disk. Highly (about 75 %) crystallized forsterite dust in the disk can reproduce the conspicuous crystalline features of the ISO observational data. This object looks to have a detached silicate and H2O ice shell with a much higher mass-loss rate. It could be a remnant of the chemical transition phase. The last phase of stellar winds of O-rich materials looks to be a superwind.

• The Journal of Korea Robotics Society
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• v.12 no.1
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• pp.42-54
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• 2017

Using an inverse of the geometric Jacobian matrix is one of the most popular ways to control robot manipulators, because the Jacobian matrix contains the relationship between joint space velocities and operational space velocities. However, the control algorithm based on Jacobian matrix has algorithmic singularities: The robot manipulator becomes unstable when the Jacobian matrix loses rank. To solve this problem, various methods such as damped and filtered inverse have been proposed, but comparative studies to evaluate the performance of these algorithms are insufficient. Thus, this paper deals with a comparative analysis of six representative singularity avoidance algorithms: Damped Pseudo Inverse, Error Damped Pseudo Inverse, Scaled Jacobian Transpose, Selectively Damped Inverse, Filtered Inverse, and Task Transition Method. Especially, these algorithms are verified through computer simulations with a virtual model of a humanoid robot, THORMANG, in order to evaluate tracking error, computational time, and multiple task performance. With the experimental results, this paper contains a deep discussion about the effectiveness and limitations of each algorithm.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.112.2-112.2
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• 2014

We propose simultaneous monitoring observations of 22 GHz $H_2O$ and 43/86/129 GHz SiO masers toward ~15 evolved stars in order to investigate spatial structure and dynamical effect from SiO to $H_2O$ maser regions including mass-loss process and development of asymmetry in circumstellar envelopes. We also aim at investigating mutual association and difference between SiO and $H_2O$ masers for establishing SiO and $H_2O$ maser models coupled to hydrodynamical model of circumstellar envelope. In addition, the correlation and difference of SiO maser properties among J=1-0, J=2-1, and J=3-2 transition masers are traced according to different type of stars for constraining SiO pumping models. These scientific goals and target sources were determined based on KVN single dish and VLBI feasibility test observations at 4 bands. As a total observing time of every 2 month monitoring, about 90 and 360 hours (in average per year) are required for single dish and VLBI observations, respectively. From the 2014B observing season, these monitoring observations will be derived as one of KVN key science programs.

• Journal of the Korean Ceramic Society
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• v.18 no.2
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• pp.75-78
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• 1981

The electrical conductivity of $(M_2O_3)_x (BaTiO_3)_{1-x}$ has been measured over the temperature range of 30 to 27$0^{\circ}C$. The substitution of rare earth oxide such as $La_2O_3$, $Nd_2O_3$, or $Dy_2O_3$ can be represented by $M_2O_3$. The additional mole fraction of the rare earth oxide is ranged over 0.0015 to 0.0030. The electrical conductivity exhibits an anomalous decrease near the tetragonal to cubic transition about 12$0^{\circ}C$. The decrease in the electrical conductivity is observed at the higher impurity concentrations owing to space charge layer. The increase in the electrical conductivity is observed as the impurity ion is varied from $La^{+3}$$Nd^{+3}$ to $Dy^{+3}$, due to overlap of 4f electrons of the inner shell.

• Lingua Humanitatis
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• v.5
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• pp.293-310
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• 2003

This study starts with a remark on the frequent usage of the term 'generation culture' in the explanations of cultural change. The term 'generation culture' itself does have neither a clear meaning nor any academic consensus for its operational definition yet. Depending on intuitions or common senses, in most cases, of everyday lift experience, the tends to designate the co-existence of different cultural layers as composing subsystems of a little broader Korean cultural trend. I tried here to analyze different positions and perspectives in the employment of this term, sometimes with strategic intentions of each social groups. Economic or political positions, for example, are intertwined with the quest of identification concerning 'we' and 'other' grouping dynamics in the Age of Globalization, which accelerates the speed of cultural re-territorialization. And the role of consumption activity as a kind of cultural indication has gained more weight in that process. This analysis will remind us, also, of the post-modem society's assumption about the space-and-time in transition, and its fluctuation.

• Korean Institute of Interior Design Journal
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• v.15 no.2 s.55
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• pp.91-98
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• 2006

The aged population increasing rapidly, the population rate of over 65 years old was over 7.5% in 2000 in Korea and it means that Korea is aging society. Increasing participation of woman in public affairs, becoming a nuclear family and increasing old aged people who want to stand alone brought about more the old households. But the aged welfare accommodation are still insufficient and more facilities accommodating the aged should be built. 80.5% of people according to poll by the Ministry of Health and Welfare responded the support of the aged is a serious problem in Korea. This result indicates the reality that the system for the aged are unsatisfied. Although these situations made a new concept of 'silver-town' of the welfare facility for the aged, it is under a transition in the aspect of the social system and the architectural aspect as well. This study will select good examples among facilities in the metropolitan area, analysis space and propose resonable program.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.2
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• pp.52.2-52.2
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• 2018

The shape of a galaxy's spectral energy distribution ranging from ultraviolet (UV) to infrared (IR) wavelengths provides crucial information about the underlying stellar populations, metal contents, and star-formation history. Therefore, analysis of the SED is the main means through which astronomers study distant galaxies. However, interstellar dust absorbs and scatters UV and optical light, re-emitting the absorbed energy in the mid-IR and Far-IR. I present the updated 3D Monte-Carlo radaitive transfer code MoCafe to compute the radiative transfer of stellar, dust emission through a dusty medium. The code calculates the emission expected from dust not only in pure thermal equilibrium state but also in non-thermal equilibrium state. The stochastic heating of very small dust grains and/or PAHs is calculated by solving the transition probability matrix equation between different vibrational, internal energy states. The calculation of stochastic heating is computationally expensive. A pilot study of radiative transfer models of SEDs in clumpy (turbulent), galactic environments, which has been successfully used to understand the Calzetti attenuation curves in Seon & Draine (2016), is also presented.

• Korean Institute of Interior Design Journal
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• v.20 no.3
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• pp.110-118
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• 2011

Today aesthetics expression could be a 'Everyday-life Beauty', because today art & design are closely related with a contemporary life. This thesis dealt with a everyday-life and sensitive design which sublimate from everyday-life material to the concept of aesthetics, such a purpose of this thesis establishes a base of everyday-life design through everyday-life aesthetics. This purpose made to pay attention to Japan's aesthetics concept, because Japan has been maintained and developed its own everyday-life aesthetics. Even if Japan doesn't have only everyday-life aesthetics, it is useful that is studies as some kind of a prototype. So this study analyzed about a everyday-life aesthetics and the expression method through the case-study of Japan. According to Yonagi Muneyoshi and Leonard Koren, the Wabi-Sabi has three conceptual characteristics like impermanent, incomplete, and imperfect and six expression characteristics like implication, tranquility, simplicity, coarseness, purity, and association. This study process is as follows. In the first a vocabulary of interior design was derived from three conceptual characteristics and six expression characteristics, and spatial facts was abstracted from it, and then volume, form, and then shape of composition facts of interior space was extracted from it. Finally the expression characteristics of the Wabi-Sabi in interior design was derived from these processes. In conclusion, the expression characteristics of the Wabi-Sabi in interior design is the transitional space through a Shadow, the conversional space through form and material composition, and the copying space through a natural friendship.