• The Bulletin of The Korean Astronomical Society
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• v.46 no.1
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• pp.37.2-37.2
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• 2021

One of the main limitations to the ground- based gravitational-wave (GW) detector sensitivity is quantum noise, which is induced by vacuum fluctuations entering the detector output port. The replacement of this ordinary vacuum field with a squeezed vacuum field has proven to be effective approach to mitigate the quantum noise in the interferometer detector and it is currently used in advanced detectors. However, the current frequency-independent squeezed vacuum cannot reduce quantum radiation pressure noise at low frequencies. A possible solution to reduce quantum noise in the broadband spectrum is the injection of frequency-dependent squeezed (FDS) vacuum. We will report the current status of squeezing experiment at KASI and introduce to the EPR (Einstein-Podolsky-Rosen) entangled state of light, which can realize FDS light without the need for an additional, external cavity.

• Korean Institute of Interior Design Journal
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• v.27 no.2
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• pp.45-54
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• 2018

Immersive space is a new type of space, which is converged with other domains and expressed in various ways and here, a mutual exchange between space and participants is realized with active intervention of participants. The purpose of this study is to examine boundary changes and characteristics in virtual space and reality or inside and outside, focusing on immersive space. For this study, a case analysis was conducted, based on the key words regarding flow experience and boundary characteristics in immersive space. The boundary characteristics extracted are as follow. First, while immersive space is overlapped in many different ways, the boundary in space gradually changes and one unique and convergent space is formed. Also, a combination of overlap is made with internal and external physical force and a convergent boundary is created. Second, forms are mixed in diverse ways and an unrealistic boundary space is revealed. For new experience, it has familiar, but new experiential characteristics and also shows an expanded boundary by the medium of different domains. Third, a simultaneous space, based on variability of time and space, has an ambiguous boundary due to a meaningless physical boundary of space and changing into a space region constantly, it becomes an unlimited variable space. Fourth, a linear expansion-based emergent space has nonlinearity, which creates a meaningless boundary, recognized as an irregular, dynamic and transformative space and expands to a creative space. In conclusion, it is anticipated that based on diverse characteristics found in immersive space, this study would give unlimited inspiration to many design fields and art creation activities and contribute to a further development through continued research on immersive space.

• Journal of The Korea Institute of Healthcare Architecture
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• v.11 no.2
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• pp.17-25
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• 2005

The purpose of this study is to suggest the direction of the specialized dementia hospital which can confront in the old age society of Korea changing quickly. We need to make the architectural planning guide including the form determining factors which is useful for the domestic dementia hospital. The factors can be extracted from a database by analysing and investigating the documents of the developed nations equips the excellent dementia hospital. The result of this study is like this : at first, it is very important that the patient has to have the feeling of comfort and familiarity through the external space leads a direct participation. Second, the interior space must have the composition for the patients primarily. So, this research can be used the basic document of the dementia hospital planning.

• Journal of Korean Association for Spatial Structures
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• v.15 no.4
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• pp.49-56
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• 2015

The roof grid of single-layer space frame structure, for Energy Core of Incheon Airport Second Terminal, is very simple and aesthetic, but it is apt to buckle under external force because of mild curvature and complex shape. The object of this study is to estimate the stability of single-layer space frame structures for Energy Core of Incheon Airport Second Terminal with the analytical conditions of structural design. The results show that the buckling load of model(pin-pin, uniform load, rigid joint), that is, the most similar model to the analytical conditions of structural design. was $10.7kN/m^2$.

• International Journal of Aeronautical and Space Sciences
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• v.6 no.2
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• pp.56-63
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• 2005

Some methods have been presented to avoid collisions among satellites for satellite formation flying mission. The potential function method based on Lyapunov's theory is known as a powerful tool for collision avoidance in the robotic system because of its robustness and flexibility. During the last decade, a potential function has also been applied to UAV's and spacecraft operations, which consists of repulsive and attractive potential. In this study, the controller is designed using a potential function via sliding mode technique for the configuration of satellite formation flying. The strategy is based on enforcing the satellite to move along the gradient of a given potential function. The new scalar velocity function is introduced such that all satellites reach the goal points simultaneously. Simulation results show that the controller drives the satellite toward the desired point along the gradient of the potential function and is robust against external disturbances.

• Bulletin of the Korean Chemical Society
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• v.31 no.1
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• pp.41-46
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• 2010

In this work, we report on the characterization of six low-$T_g$ poly[methyl-3-(9-carbazolyl) propylsiloxane] based photorefractive (PR) composites sensitized with poly(3-hexylthiophene) (P3HT) in different concentrations, ranging from 0.2 to 1 wt %. At 632.8 nm, photoconductivity, space charge field, refractive index modulation, and grating buildup time were measured versus external electric field. The photoconductivity was strongly dependent on the visible light absorption and mobility. The magnitude of space charge field was affected by the conductivity contrast $\sigma_{ph}/(\sigma_{ph}+\sigma_d)$. The refractive index modulation increased with the magnitude of space charge field and the PR grating buildup speed increased with the photoconductivity.

• Transactions on Electrical and Electronic Materials
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• v.16 no.3
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• pp.107-111
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• 2015

Our work is based on the development of a numerical model to develop a methodology for predicting the aging and breakdown in insulation due to the dynamics of space charge packets. The model of bipolar charge transports is proposed to simulate space charge dynamic for high DC voltage in law-density polyethylene (LDPE), taking into account the trapping and detrapping of recombination phenomena, this model has been developed and experimentally validation. Theoretical formulation of the physical problem is based on the Poisson, the continuity and the transport equations as well as on the appropriate models for injection. Numerical results provide temporal and local distributions of the electric field, the space charge density for the different kinds of charges, conduction and displacement current densities, and the external current.

• Journal of Astronomy and Space Sciences
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• v.32 no.1
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• pp.1-11
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• 2015

Earth's magnetopause separating the fast and often turbulent magnetosheath and the relatively stagnant magnetosphere provides various forms of free energy that generate low-frequency surface waves. The source mechanism of this energy includes current-driven kinetic physical processes such as magnetic reconnection on the dayside magnetopause and flux transfer events drifting along the magnetopause, and velocity shear-driven (Kelvin-Helmholtz instability) or density/pressure gradient-driven (Rayleigh-Taylor instability) magnetohydro-dynamics (MHD) instabilities. The solar wind external perturbations (impulsive transient pressure pulses or quasi-periodic dynamic pressure variations) act as seed fluctuations for the magnetopause waves and trigger ULF pulsations inside the magnetosphere via global modes or mode conversion at the magnetopause. The magnetopause waves thus play an important role in the solar wind-magnetosphere coupling, which is the key to space weather. This paper presents recent findings regarding the generation of surface waves (e.g., Kelvin-Helmholtz waves) at the Earth's magnetopause and analytic and observational studies accountable for the linking of the magnetopause waves and inner magnetospheric ULF pulsations, and the impacts of magnetopause waves on the dynamics of the magnetopause and on the inner magnetosphere.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.1252-1254
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• 2003

Debris flows associated with landslides occur as one of the most devastating natural disasters that threat Taiwan. Typically, three essential factors are needed simultaneously to trigger debris flow, namely sufficient soils and rocks, favorable slope, and abundant water. Among the three essentials, the slope is natural and static without external forcing, while the landslide is generally induced by earthquake or rainfall events, and the water is produced by heavy rainfall events. In this study, we analyzed the landslides triggered by the typhoons Herb (1996) and typhoon Troaji (2001). It is concluded that the statistical data are useful to quantify the threshold of the potential landslide area. Then, the possibility to prevent the debris flow occurrence may be increased.

• The Journal of Korea Robotics Society
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• v.14 no.4
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• pp.311-317
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• 2019

Direct teaching is an essential function for collaborative robots for easy use by non-experts. For most robots, direct teaching is implemented only in joint space because the realization of Cartesian space direct teaching, in which the orientation of the end-effector is fixed while teaching, requires a measurement of the end-effector force. Thus, it is limited to the robots that are equipped with an expensive force/torque sensor. This study presents a Cartesian space direct teaching method for torque-controlled collaborative robots without either a force/torque sensor or joint torque sensors. The force exerted to the end-effector is obtained from the external torque which is estimated by the disturbance observer-based approach with the friction model. The friction model and the estimated end-effector force were experimentally verified using the robot equipped with joint torque sensors in order to compare the proposed sensorless approach with the method using torque sensors.