• International Journal of High-Rise Buildings
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• v.6 no.4
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• pp.327-332
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• 2017

This paper discusses several topics associated with the densification caused by supertall buildings and their impact on city systems. The paper covers five key areas where a supertall tower creates a concentration of needs and effects. First, the paper comments on population shifts towards the city and how they affect carbon footprint, utilities infrastructure and transport. The effect of single- and mixed-use towers is discussed in the context of population density. The second section brings the issues of transit, accessibility and master planning into focus. The use and criticality of public transport, cycling and walking is described. Servicing and deliveries using freight consolidation and shared systems is also discussed along with their contribution to the culture of sustainable travel. In the third section the paper reflects on supertall buildings' below-ground utilities and drainage provision, particularly the challenges faced in established city infrastructures. The utilities issues associated with supertall concentration (in land-use terms) compared to equivalent low-rise distribution is also commented on in the context of surface water runoff. In the fourth section, the topic of supertall sustainability is discussed and how city systems need to respond to create desirable and affordable space for occupiers. The changing need for vertical communities, 'stacked neighbourhoods' and the notion of a micro-city is described. Finally, the paper considers the energy consumption and resilience of supertall buildings in the context of basic geometry, façade design, climate and mixed-use benefits as they impact city systems.

• Journal of The Korean Astronomical Society
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• v.36 no.3
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• pp.105-110
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• 2003

Recent observations of galaxy clusters in radio and X-ray indicate that cosmic rays and magnetic fields may be energetically important in the intracluster medium. According to the estimates based on theses observational studies, the combined pressure of these two components of the intracluster medium may range between $10\%{\~}100\%$ of gas pressure, although their total energy is probably time dependent. Hence, these non-thermal components may have influenced the formation and evolution of cosmic structures, and may provide unique and vital diagnostic information through various radiations emitted via their interactions with surrounding matter and cosmic background photons. We suggest that shock waves associated with cosmic structures, along with individual sources such as active galactic nuclei and radio galaxies, supply the cosmic rays and magnetic fields to the intracluster medium and to surrounding large scale structures. In order to study 1) the properties of cosmic shock waves emerging during the large scale structure formation of the universe, and 2) the dynamical influence of cosmic rays, which were ejected by AGN-like sources into the intracluster medium, on structure formation, we have performed two sets of N-body /hydrodynamic simulations of cosmic structure formation. In this contribution, we report the preliminary results of these simulations.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.67-67
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• 2012

Exploring the distant universe by observing various astronomical objects and extending knowledge on the cosmos by applying human intuition and reasoning to observations are astronomers' professional activity. Astronomers are the people born under a lucky star since this elegant and beautiful job is their the only duty. Being in the 21st century we astronomers now know that galaxies are holding evolving stars and gas, and distribute in the infinite spacetime in an interesting way revealing the secrets of the beginning of the universe. Cosmic structures such as galaxies, large-scale structures, and cosmic microwave background fluctuations are also the tracers of the expansion of space and the invisible components of the energy contents of the universe. Unlike the past century we are in a situation where integral knowledge on various cosmic structures as well as that on a variety of observational and analysis tools are available to everyone and often required for our special mission. However, my experience made me think that accumulating critical questions on nature driven by curiosity is vital for researchers and far more important than absorbing knowledge from others and books. Transforming one's own question marks to acclamation marks is the reward of our life. That is THE fun.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.134.2-134.2
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• 2012

Discrete auroras, with unique shapes embedded in diffuse auroras, are generally associated with precipitating electrons that originate from the plasma sheet and are accelerated on the way as they travel to polar regions along the field lines. Two acceleration mechanisms have been proposed: quasi-static electric fields and dispersive Alfven waves, which are believed to yield monoenergetic peaks and broadband features in the particle spectra, respectively. Hence, it should be interesting to see how the two different mechanisms, through their characteristic spectra of the accelerated electrons, produce distinct auroral images and spectra, especially in the far ultraviolet (FUV) wavelengths as the long and short Lyman-Birge-Hopfield (LBH) bands exist as well as the strong absorption band of molecular oxygen in the FUV band. In fact, we have previously shown, using the simultaneous observations of precipitating electrons and the corresponding FUV spectra, that the discrete auroras associated with inverted-V events have a stronger relative intensity of the long LBH to the short LBH compared to diffuse auroras, especially when the peak energy is above a few keV. In this paper, we would like to focus on the differences in the FUV images and spectra between the two discrete auroras of the monoenergetic and broadband cases, again based on the study using the dataset of simultaneous observations of particles and FUV spectral images.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.213.1-213.1
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• 2012

우주방사선폭풍탐사선 (Space Radiation Storm probe: SRSP)에 탑재할 과학측정 장비들 중의 하나로 추진 중인 PD는 우주방사선 환경에서의 태양활동에 따른 고에너지 하전입자들 특히 proton의 에너지와 flux에 대한 정보를 획득하고 더불어 다른 고에너지 입자의 효과까지 포함하는 Linear Energy Transfer (LET)을 측정하기 위한 탑재체이다. 본 연구팀은 PD의 사양을 결정하기 위해서 GEANT4를 사용하여 전산모사를 수행하였으며, proton의 경우 우주 방사선 환경에서의 태양활동에 따른 고에너지 영역을 고려하여 0.1 ~ 1000 MeV 범위에서 전산 모사를 수행하였다. 본 연구팀은 특히 PD의 에너지 범위를 0 MeV ~ 5 MeV, 5 MeV ~ 10 MeV, 10 MeV ~ 20 MeV, 20 MeV ~ 35 MeV, 35 MeV ~ 52 MeV, 52 MeV ~ 72 MeV, 72 MeV 이상으로 총 7개의 channel를 결정하고 Al의 blocking material을 사용하여 검출하려는 에너지 범위를 조절한다. 또한 최적의 채널을 결정하여 silicon detector를 사용한 탑재체의 개념 설계를 실시하였다. 설계된 PD로부터 방사선대에서의 proton를 측정함으로써 태양기원 고에너지 입자에 대한 포획 및 쇠퇴에 대한 이해를 도울 것이다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.327-334
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• 2004

Spectroscopic and electrostatic probe measurements were made to examine plasma characteristics with or without a metal plate for a 10-㎾-class direct-current arcjet Heat fluxes into the plate from the plasma were also evaluated with a Nickel slug and thermocouple arrangement. Ammonia and mixtures of nitrogen and hydrogen were used. The NH$_3$ and $N_2$+3H$_2$ plasmas in the nozzle and in the downstream plume without a plate were in thermodynamical nonequilibrium states. As a result, the H-atom electronic excitation temperature and the $N_2$ molecule-rotational excitation temperature intensively decreased downstream in the nozzle although the NH molecule-rotational excitation temperature did not show an axial decrease. Each temperature was kept in a small range in the plume without a plate except for the NH rotational temperature for NH$_3$ gas. On the other hand, as approaching the plate, the thermodynamical nonequilibrium plasma came to be a temperature-equilibrium one because the plasma flow tended to stagnate in front of the plate. The electron temperature had a small radial variation near the plate. Both the electron number density and the heat flux decreased radially outward, and an increase in H$_2$ mole fraction raised them at a constant radial position. In cases with NH$_3$ and $N_2$+3H$_2$ a large number of NH radical with a radially wide distribution was considered to cause a large amount of energy loss, i.e., frozen flow loss, for arcjet thrusters.

• Multiscale and Multiphysics Mechanics
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• v.1 no.3
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• pp.225-231
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• 2016

The formation of silicon-on-nothing (SON) structure during an annealing process from the silicon substrate including the trench structures has been considered as an effective technique to construct the structure that has an empty space under the closed flat surface. Previous studies have demonstrated the mechanism of the formation of SON structure, which is based on the surface diffusion driven by the minimization of their surface energy. Also, it has been fragmentarily shown that the morphology of SON structure can be affected by the initial design of trench (e.g., size, number) and the annealing conditions (e.g., temperature, pressure). Based on the previous studies, here, we report a comprehensive study for the design of the cavity-embedded structure (i.e., SON structure). To do this, a dynamic model has been developed with the phase field approach. The simulation results represent that the morphology of SON structures could be detailedly designed, for example the position and thickness of cavity, the thickness of top and bottom layer, according to the design parameters. This study will give us an advantage in the effective design of SON structures.

• Korean Journal of Materials Research
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• v.30 no.11
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• pp.636-640
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• 2020

Due to the serious air pollution problem, interest in eco-friendly vehicles is increasing. Solving the problem of pollution will necessitate the securing of high energy storage technology for batteries, the driving force of eco-friendly vehicles. The reason for the continuing interest in the transition metal oxide LiMO₂ as a cathode material with a layered structure is that lithium ions reveal high mobility in two-dimensional space. Therefore, it is important to investigate the effective intercalation and deintercalation pathways of Li⁺, which affect battery capacity, to understand the internal structure of the cathode particle and its effect on the electrochemical performance. In this study, for the cathode material, high nickel Ni_0.8Co_0.1Mn_0.1(OH)₂ precursor is synthesized by controlling the ammonia concentration. Thereafter, the shape of the primary particles of the precursor is investigated through SEM analysis; X-ray diffraction analysis is also performed. The electrochemical properties of LiNi_0.8Co_0.1Mn_0.1O₂ are evaluated after heat treatment.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.7
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• pp.541-548
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• 2006

A hybrid ventilation system was introduced to predict the ventilation performance of the apartments. This ventilation system was composed of the natural supply-air inlet and the forced exhaust-air outlet. Analysis was conducted by CFD technique and was performed on three ventilating flow rates; 30, 60, $120m^3/h$. As the results, residents feel comfortable thermally for $60m^3/h$. In the case of $120m^3/h$, however, residents feel uncomfortable both thermally and in air currents. In this study the energy saving for space heating is also an important factor. In the case of whole region with $180m^3/h$, residents feel comfortable at each region of the model apartment. It is shown that this hybrid ventilation system is possible method for the apartment house.

• 한국태양에너지학회:학술대회논문집
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• 2009.11a
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• pp.285-290
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• 2009

The main thrust of this paper is to investigate acceptable supply air conditions of a dedicated outdoor air system (DOAS) for highrise apartment buildings. As for a typical $132-m^2$ apartment unit, it was assumed that centralized DOAS-Ceiling Radiant Cooling Panel was installed. Transient behavior and control characteristics of each system were modeled numerically using a commercial equation solver program. The optimized dew point temperature of the DOAS was discussed on the basis of the ASHRAE standard 62.1-2007 and the current Korean ventilation standard for apartments. It was found that the optimized dew point temperature of the DOAS supply air accommodating total latent load of a space is $11-12^{\circ}C$ and the appropriate supply air temperature of the DOAS is $11-12^{\circ}C$ in cooling period and neutral temperature of $18-20^{\circ}C$ in intermediate period.