• Journal of Digital Convergence
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• v.16 no.8
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• pp.263-267
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• 2018

In this study, it is aimed to solve the problems of energy depletion, environmental pollution, climate change and traffic congestion in the coming generations. In Korea, the usage of public bicycle, which is a short-distance transportation system, is continuously increasing. Therefore, we analyzed the public bicycles of 'Taungryei' in Seoul and 'Nubiza' in Changwon City. We also conducted in-depth interviews with Stephen Anderson based on six principles of Creating Pleasurable Interfaces. As a result, users' discomfort was found in the functional part and the usability part of the public bicycle. Also, it was confirmed that the users were satisfied with the public bicycle in the meaningful part. Therefore, public bicycles should consider the user experience aspects to complement functional and usability parts for users.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.37 no.6
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• pp.417-426
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• 2019

Conventional visualization of PM (Particulate Matter)10 flows applies superimposition of concentration distribution maps and wind field maps. This method is efficient for small scale maps where only macro flow trends are of interest. However, in the case of urban areas, local flows are difficult to model at micro level using wind fields, and therefore different methods of flow extraction is deemed necessary. In this study, flow information is extracted and visualized directly from the PM10 density data by using the gravity model. This method has the advantage that additional information such as wind field is not necessary for estimating the intensity and direction of PM10 flow. The extracted spatio-temporal flow patterns of PM10 are analyzed with relation to traffic information.

• Journal of Applied Reliability
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• v.14 no.4
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• pp.213-219
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• 2014

Wind turbine, which is attracting part of the renewable energy and is researching continuously, is going to be large size for high efficiency. There is a yaw system rotating the nacelle, weighted about 600 tons, to be perpendicular with the wind direction blowing in the large wind turbine. The wind turbine is focusing on the reliability improvement because working environment effect is bigger than any other points and specially, the reliability improvement of the yaw drive is required by the customer because it is the key component of the wind turbine. Because of this, the establishment of criteria for yaw drive is required because yaw drive system is the part of the wind turbine closely related with ensuring the reliability. So, this study did the failure analysis of the yaw drive system, which is consisted with 10 sets of yaw drives through researching and analyzing the site conditions. Also this study designed the life test method based on the failure analysis and working condition of the yaw drive. To design the accelerated life test of the yaw drive, this study reviewed the torque, lubrication condition, and frequency of use and etc. Finally, this selected the torque as the acceleration factor which is affected mainly to the system and also, the test equipment was developed based on the requirement of the life and performance test.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.1
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• pp.81-94
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• 2015

The purpose of this study is to find ways to build a desirable risk governance to respond to these uncertainties like such as increased risk due to the rapid development of modern science and technology in S. Korea. This study is about model of risk communication with scientific technology for additional construction of nuclear power plants. This study analyzed risk communication with scientific technology through new explanatory models between approval opinions of scientific professional group and opposition opinions of the public with Kori nuclear power plant of S. Korea. And then This study investigated related system for policy promotion in the field of nuclear energy of the current S. Korea. Consequently, Governance to strengthen the negotiations on nuclear technology at the time of the interaction in risk communication have been identified and the future of policy direction of the Korean Standard Nuclear Power Plant was detected.

• Journal of the Korean earth science society
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• v.25 no.7
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• pp.629-636
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• 2004

In order to study developments of the marine atmosphere boundary layer in cloud incoming, important parameters like heat advection, surface layer heat flux, and radiation energy were estimated using the rawinsonde, AWS data, satellite images, and buoy data which was installed at the East Sea. We explained the variation and the development of mixed layer in terms of surface layer heat flux and long wave radiation under the cloudy sky. The heat flux was obtained by means of the bulk method. Conservation of heat was analysed by heat budget equation, which was consist of buoy data in the East sea, and sounding data at Ulleungdo and at Pohang. During the inflow of cloud, radiative cooling at the surface after was suppressed and long wave radiation from cloud played a role of warming. The surface layer temperature was also remained warm by influence of warm advection from south-easterly direction. The air temperature in night was increased, as a result, mixed layer was not destroyed and The nocturnal boundary layer was composed of the mixed layer and the residual layer.

• Journal of Environmental Science International
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• v.8 no.3
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• pp.299-307
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• 1999

In order to fast predict the wind-driven current in a small bay, a convolution method in which the wind-driven current can be generated only with the local wind is developed and applied in the idealized bay and the idealized Sachon Bay. The accuracy of the convlution method is assessed through a series of the numerical experiements carried out in the jidealized bay and the idealized Sachon Bay. The optimum response function for the convolution method is obtained by minimizing the root man square (rms) difference between the current given by the numerical model and the current given by the convolution method. The north-south component of the response function shows simultaneous fluctuations in the wind and wind-driven current at marginal region while it shows "sea-saw" fluctuations (in which the wind and wind-driven current have opposite direction) at the central region in the idealized Sachon Bay. The present wind is strong enough to influence on the wind-driven current especially in the idealized Sachon Bay. The spatial average of the rms ratio defined as the ratio of the rms error to the rms speed is 0.05 in the idealized bay and 0.26 in the idealized Sachon Bay. The recover rate of kinetic energy(rrke) is 99% in the idealized bay and 94% in the idealized Sachon Bay. Thus, the predicted wind-driven current by the convolution model is in a good agreement with the computed one by the numerical model in the idealized bay and the idealized Sachon Bay.achon Bay.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.2
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• pp.36.3-37
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• 2015

4C39.25 (0923+392) is a distant radio loud AGN placed at redshift 0.695. The motivation of our work is peculiar properties 4C39.25. Firstly, it has a conspicuous distinction of jet direction between kilo-parsec scale observation made by VLA (Kollgaard et al. 1990) and the parsec scale observation by VLBA (Kellermann et al. 1998). This might indicate episodic-jet activity which recently turned on. This object currently shows two stationary compact parsec-scale components which are bright jet component on east and less luminous core on west. Also, it is known that there have been superluminal jet components which are flowing from the core toward east, and then merging with the bright jet component (Marscher et al. 1991, Alberdi et al. 2000, Lister et al. 2013). Although 4C39.25 seems to be a blazar-like source having broad emission lines (SDSS) and superluminal motion, its property that jet component is brighter than the core is different from ordinary blazars. Furthermore, it has young radio galaxy-like properties such as non-variation in total flux (Alberdi et al. 1997, 2000, MOJAVE database) and high frequency peak at spectral energy distribution (Orienti et al 2007). Such complex properties led us to make recent observations to reveal precise properties and new changes of the source. We used Korean VLBI Network (KVN) and VLBI Exploration of Radio Astronomy (VERA) Array (KaVA) which provide high-frequency (23GHz and 43GHz) and high spatial resolution (1.2mas and 0.6mas). Therefore, this system is suitable for morphological and physical research on parsec scale structure. We present results for several epochs observed during 2013 to 2014, mainly focusing on morphological changes of 4C39.25 using KaVA images.

• Journal of the Korean Electrochemical Society
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• v.15 no.2
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• pp.74-82
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• 2012

Proton exchange membrane fuel cell performance is changed by the complicated physical phenomenon. In this study, water discharge performance of proton exchange membrane fuel cell were performed numerically to compare serpentine channel flow fields of 5-pass 4-turn serpentine and 25 $cm^2$ reaction surface between with and without sub-channel at the rib. Through the supplement of sub channel flow field, it is shown from the results that water removal characteristic inside channel improves because the flow direction of under-rib convection is changed into the sub channel. Reacting gases supplied from entrance disperse into sub channel flow field and electrochemical reaction occurs uniformly over the reaction surface. The results obtained that total current density distributions become uniform because residence time of reacting gases traveling to sub-channel flow field is longer than to main channel.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.4 no.1
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• pp.63-70
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• 1994

Single crystals of the superionic conductor ${\beta}-Ag_3SI$ were prepared by thermal treatmentr from the reactant mixture of AgI and $Ag_2S$. The growing single crystals were made to spherical shape of $200{mu}m$ in diameter. The detailed structures analyses revealed that $Ag^+$ in ${\beta}-Ag_3SI$ distribute on 12h site of 4-coordination inpreference to 3c site of 6-coordination. The effective one-particle potential (o.p.p.). of $Ag^+$ along [110] direction was evaluated from the probability density function(p.d.f.) Activation energy calculated from the o.p.p. curve has been found to be 0.012 eV for the diffusion of $Ag^+$ on (001) plane in the ${\beta}-Ag_3SI$ structure.

• Progress in Medical Physics
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• v.14 no.1
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• pp.1-7
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• 2003

In this work we developed a EGS4 control code to calculate the dose distributions for high energy electron beams in water phantom applied longitudinal magnetic field. We reviewed the electron's motion in magnetic field and delivered equations for direction changs of the electron by the external magnetic field. The mathematical results are inserted into the EGS4 code system to account for the presence of external magnetic fields in phantom. The electron pencil beam paths of 6 MeV in water phantom are calculated for magnetic fields of 1-3 T and the dose distributions for a field of 1.0 cm in diameter are calculated for magnetic fields of 0.6-1 T using the code. From the results of path calculations we found that the lateral ranges of the electrons are reduced in the magnetic field of 3 T. For a field of 1 cm diameter and a magnetic field of 1 T, the small dose enhancement near the range of the electrons on the depth dose and the penumbra reduction of 0.15 cm on the beam profile are observed. We discussed and evaluated the results from the theoretical concepts.