• Journal of the Korean Institute of Landscape Architecture
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• v.28 no.4
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• pp.132-137
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• 2000

In June, the City of Seoul held a design competition for $\ulcorner$Seoul Park$\lrcorner$in Paris to promote friendly relations with its sister city. The purpose of this paper is to articulate the design concept of a scheme submitted by the author. The author interpreted the object of this design competition as follows: if we regards a park not as one of urban planning facilities but as a space for expressing a culture, $\ulcorner$Seoul Park$\lrcorner$in Paris is a space expressing Korean culture, or a culture of the City of Seoul in Paris, France. Three points were emphasized in this scheme: 1. Physical and non-physical aspects of Korean culture, or a culture of the City of Seoul were expressed separately. In physical part, a traditional Korean garden was reappeared to express its authenticity compared to its counterpart, French classical garden - its formal and grand style. In nonphysical part, Seoul's features and its citizen's facial expression were engraved on 'free standing walls' named 'Seoul Expression'. In addition, Korean traditional and modern performing arts will be performed in a square named as 'Seoul madang' surrounded by the free standing walls. 2. A space clearly divided by the fence was necessary to distinguish a traditional Korean garden from the place which looks like an amusement park. Traditional wall, mounding and pine tree groves were included. 3. Bamboo grove with the way taking a walk was introduced. The author expected that Parisian feels oriental mystery, the sound of wind, and the time lag of past and present in this sounding bamboo grove.

• Korean Journal of Remote Sensing
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• v.37 no.6_2
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• pp.1819-1827
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• 2021

Land-use/cover change caused by rapid urbanization in South Korea is one of the concerns in flood risk management because groundwater recharge by precipitation hardly occurs due to an increase in impermeable surfaces in urban areas. This study investigated the hydrologic effects of land-use/cover on groundwater recharge in the Yeonje-gu district of Busan, South Korea. A statistical time series analysis was conducted with temporal variations of precipitation and groundwater level to estimate lag-time based on correlation coefficients calculated from auto-correlation function (ACF), cross-correlation function (CCF), and moving average (MA) at five sites. Landform and land-use/cover within 250 m radius of the monitoring wells(GW01, GW02, GW03, GW04, and GW05) at five sites were identified by land cover and digital map using Arc-GIS software. Long lag-times (CCF: 42-71 days and MA: 148-161 days) were calculated at the sites covered by mainly impermeable surfaces(GW01, GW03, and GW05) while short lag-times(CCF: 4 days and MA: 67 days) were calculated at GW04 consisting of mainly permeable surfaces. The results suggest that lag-time would be one of the good indicators to evaluate the effects of land-use/cover on estimating groundwater recharge. The results of this study also provide guidance on the application of statistical time series analysis to environmentally important issues on creating an urban green space for natural groundwater recharge from precipitation in the city and developing a management plan for hydrological disaster prevention.

• Journal of The Korean Astronomical Society
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• v.52 no.4
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• pp.109-119
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• 2019

While the reverberation mapping technique is the best available method for measuring black hole mass in active galactic nuclei (AGNs) beyond the local volume, this method has been mainly applied to relatively low-to-moderate luminosity AGNs at low redshift. We present the strategy of the Seoul National University AGN Monitoring Project, which aims at measuring the time delay of the $H{\beta}$ line emission with respect to AGN continuum, using a sample of relatively high luminosity AGNs out to redshift z ~ 0.5. We present simulated cross correlation results based on a number of mock light curves, in order to optimally determine monitoring duration and cadence. We describe our campaign strategy based on the simulation results and the availability of observing facilities. We present the sample selection, and the properties of the selected 100 AGNs, including the optical luminosity, expected time lag, black hole mass, and Eddington ratio.

• Membrane Journal
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• v.25 no.3
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• pp.248-255
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• 2015

Aminated polyetherimide membrane synthesized in the laboratory according to amine ratio was used for measurement of gas permeability, diffusivity, and solubility about carbon dioxide, nitrogen, methane, oxygen, and sulfur dioxide with Time-lag method at room temperature. Generally, gas permeability is totally decreased because the more amination rate reacted to the main chain of amine groups, the more intermolecular space became narrow. However, gas permeability of sulfur dioxide was increased due to combination of sulfur dioxide and amine groups have acid and base properties respectively. Diffusivity and solubility of dry gas are totally decreased excluding sulfur dioxide as increasing amination rate. In case of sulfur dioxide, however, diffusivity as well as solubility was increased as increasing amination rate. Selectivity of carbon dioxide/nitrogen showed 60 when amination rate was 3. In case of humid gas, gas permeability of carbon dioxide was 70 barrer when relative humidity showed 100, and selectivity with nitrogen approximately showed 18.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.7
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• pp.13-19
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• 2007

This study relates to a new high-speed drive method for the full-HD PDP with 1080 horizontal scanning lines. The characteristics of the new drive method is evaluated considering the characteristics of the display discharge by the high-speed addressing. In this drive method, if the width of the address pulse narrows, the relati0[V]e discharge strength and the discharge time lag of the first display discharge are received the influence of it. Though the change in the applied position of the address pulse is unrelated to the discharge strength, it influences at the discharge time lag. However, the stable display discharges can be induced regardless of the address pulse position and width if the address pulse position is within [$6{\mu}s$] and the width is up to [$0.7{\mu}s$]. From the experiments, it has been understood that the high-speed drive technique with the address pulse of narrow width is sensitively influenced by the space charge because of the insufficiency of wall charge.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.1
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• pp.28.3-29
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• 2017

We present the results of very long baseline interferometry (VLBI) observations of gamma-ray bright blazar S5 0716+714 using the Korean VLBI Network (KVN) at the 22, 43, 86, and 129 GHz bands, which are part of the KVN key science program known as the Interferometric Monitoring of Gamma-ray Bright AGNs (iMOGABA). Multi-frequency VLBI observations were conducted in 29 sessions from January 16, 2013 to March 1, 2016. The source was detected and imaged in all available frequency bands. For all observed epochs, the source is compact on the milliarcsecond (mas) scale, yielding a compact VLBI core dominating the synchrotron emission on the mas scale. Based on the multi-wavelength data at 15 and 230 GHz, we found that the source shows multiple prominent enhancements of the flux density at the centimeter (cm) and millimeter (mm) wavelengths, with mm enhancements leading cm enhancements with a time lag of $18{\pm}5$ days. Turnover frequency is found to vary over our observations between 22 to 69GHz. Taking into account the synchrotron self-absorption model of the relativistic jet in S5 0716+714, we estimated the magnetic field strength in the mas emission region to be 0.4-66 mG during the observing period, finding that the magnetic field strength is strongly correlated with the turnover frequency and the relatively strong magnetic field (e.g., B > 40 mG) is correlated with flux enhancements at mm wavelengths (e.g., 86 GHz).

• Journal of Korea Water Resources Association
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• v.33 no.2
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• pp.159-167
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• 2000

The purpose of this study is to estimate the stochastic monthly runoff model for the Kunwi south station of Wi-stream basin in Nakdong river system. This model was based on the theory of Box-Jenkins multiplicative ARlMA and the state-space model to simulate changes of monthly runoff. The forecasting monthly runoff from the pair of estimated effective rainfall and observed value of runoff in the uniform interval was given less standard error then the analysis only by runoff, so this study was more rational forecasting by the use of effective rainfall and runoff. This paper analyzed the records of monthly runoff and effective rainfall, and applied the multiplicative ARlMA model and state-space model. For the P value of V AR(P) model to establish state-space theory, it used Ale value by lag time and VARMA model were established that it was findings to the constituent unit of state-space model using canonical correction coefficients. Therefore this paper confirms that state space model is very significant related with optimization factors of VARMA model.

• Structural Engineering and Mechanics
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• v.34 no.3
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• pp.285-300
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• 2010

The two-dimensional deformation of a homogeneous, isotropic thermoelastic half-space with voids with variable modulus of elasticity and thermal conductivity subjected to thermomechanical boundary conditions has been investigated. The formulation is applied to the coupled theory(CT) as well as generalized theories: Lord and Shulman theory with one relaxation time(LS), Green and Lindsay theory with two relaxation times(GL) Chandrasekharaiah and Tzou theory with dual phase lag(C-T) of thermoelasticity. The Laplace and Fourier transforms techniques are used to solve the problem. As an application, concentrated/uniformly distributed mechanical or thermal sources have been considered to illustrate the utility of the approach. The integral transforms have been inverted by using a numerical inversion technique to obtain the components of displacement, stress, changes in volume fraction field and temperature distribution in the physical domain. The effect of dependence of modulus of elasticity on the components of stress, changes in volume fraction field and temperature distribution are illustrated graphically for a specific model. Different special cases are also deduced.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.1
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• pp.26-31
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• 2014

This study looks into changing building energy use by application of phase change material (PCM). PCM does not need extra energy for operation and is used for reducing building energy use and, CO2 output by displaying semi-permanent effects after installation. It also is able to avoid the maximum electric power time-zone by inducing a time lag phenomenon of cooling and heating loads with high thermal capacity using latent heat. To verify the efficiency of blinds and PCM, tests about the PCM operation mechanism using air conditioning machinery and nocturnal panel cooling were done. In the test results of the case using PCM installation, a $45^{\circ}$ blind angle with machinery air conditioning and nocturnal panel cooling at the same time shows a 22 percent energy saving effect against general space. The test results of each case were compared and analyzed based on the blind and window opening settings. Finally, the energy reduction of existing buildings using PCM application was reviewed based on the final measurement results.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.3
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• pp.8-16
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• 2002

The implicit formulation of rotor dynamics for helicopter flight simulation has been derived and and presented. The generalized vector kinematics regarding the relative motion between coordinates were expressed as a unified matrix operation and applied to get the inertial velocities and accelerations at arbitaty rotor blade span position. Based on these results the rotor aeromechanic equations for flapping dynamics, lead-lag dynamics and torque dynamics were formulated as an implicit form. Spatial integration methods of rotor dynamic equations along blade span and the expanded applicability of the present implicit formulations for arbitrary hings geometry and hinge sequences have been investigated. Time integration methods for present DAE(Differential Algebraic Equation) to calculate dynamic response calculation are recommenaded as future works.