• International Journal of Aeronautical and Space Sciences
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• v.13 no.3
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• pp.386-397
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• 2012

The stability and structure of bluff-body stabilized hydrogen flames were investigated numerically and experimentally. The velocity of coflowing air was varied from subsonic velocity to a supersonic velocity of Mach 1.8. OH PLIF images and Schlieren images were used for analysis. Flame regimes were used to classify the characteristic flame modes according to the variation of the fuel-air velocity ratio, into jet-like flame, central-jet-dominated flame, and recirculation zone flame. Stability curves were drawn to find the blowout regimes and to show the improvement in flame stability with increasing lip thickness of the fuel tube, which acts as a bluff-body. These curves collapse to a single line when the blowout curves are normalized by the size of the bluff-body. The variation of flame length with the increase in air flow rate was also investigated. In the subsonic coflow condition, the flame length decreased significantly, but in the supersonic coflow condition, the flame length increased slowly and finally reached a near-constant value. This phenomenon is attributed to the air-entrainment of subsonic flow and the compressibility effect of supersonic flow. The closed-tip recirculation zone flames in supersonic coflow had a reacting core in the partially premixed zone, where the fuel jet lost its momentum due to the high-pressure zone and followed the recirculation zone; this behavior resulted in the long characteristic time for the fuel-air mixing.

• Computers and Concrete
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• v.12 no.2
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• pp.211-228
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• 2013

The structure analyzed in this paper has particular building style and special structural system. It is a rigid-connected twin-tower skyscraper with asymmetrical distribution of stiffness and masses in two towers. Because of the different stiffness between the north and the south towers, the torsion seismic vibration is significant. In this paper, in order to study the seismic response of the structure under both frequent low-intensity earthquakes as well as rare earthquakes at the levels of intensity 7, the analysis model is built and analyzed with NosaCAD. NosaCAD is an nonlinear structure analysis software based on second-development of AutoCAD with ObjectARX. It has convenient modeling function, high computational efficiency and diversity post-processing functions. The deformations, forces and damages of the structure are investigated based on the analysis. According to the analysis, there is no damage on the structure under frequent earthquakes, and the structure has sufficient capacity and ductility to resist rare earthquakes. Therefore the structure can reach the goal of no damage under frequent earthquakes and no collapse under rare earthquakes. The deformation of the structure is below the limit in Chinese code. The time sequence and distribution of damages on tubes are reasonable, which can dissipate some dynamic energy. At last, according to forces, load-carrying capacity and damage of elements, there are some suggestions on increasing the reinforcement in the core tube at base and in stiffened stories.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.3
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• pp.105-111
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• 2020

We defined Jeju Wind Castle and analyzed the relationship between Hallasan-Oreum-Batdam, the main subject, for the first time. In Jeju, 1.5m high Batdam(Black Silk Road), 368 Oreums, Hallasan Mountain 1950m are all unique scenery. The verification of this paper demonstrates that Samdasoo's groundwater extraction sea level is equal to the height of Hallasan and that this problem is mathematically complete in neutral plane theory. Donnaeko(700meters above sea level)-Baeknokdamdongneung-Jindallebat-Seongpanak-Gyorae(453 meters)-Witsaeoreum(1700meters) is a rain belt that hits the low-air pressure air-conditioned North Pacific humidity rising from the southeast and the high-pressure cold air of Hallasan Peak. It rains a lot because - and + are neutral plane, which adds to zero. Hallasan is called Jinsan in Jeju history. The answer is Wind Castle. The number of Oreum in Jeju is 369 including Hallasan, and Batdam, which is about 1.5m high, does not collapse even with a typhoon blowing over 50m/s. Because the wind castle's core is 1.5 meters of Batdam and it is a triangular number.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.95-95
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• 2014

The mass measurement of neutron stars or black holes is of fundamental importance in our understanding of the evolution of massive stars and core-collapse supernova explosions as well as some exotic physics of the extreme conditions. Despite the importance, however, it's very difficult to measure mass of these objects directly. One way to do this, if they are in binary systems, to measure their binary motions (i.e., Doppler shifts) which can give us direct information on their mass. Recently many new highly-obscured massive X-ray binaries have been discovered by new hard X-ray satellites such as INTEGRAL and NuSTAR. The new highly-obscured massive X-ray binaries are faint in the optical, but bright in the infrared with many emission lines. Based on the near-infrared spectroscopy, one can first understand the nature of stellar companions to the compact objects, determining its spectral types and luminosity classes as well as mass losses and conditions of (potential) circumstellar material. Next, spectroscopic monitoring of these objects can be used to estimate the mass of compact objects via measuring the Doppler shifts of the lines. For the former, broad-band spectroscopy is essential; for the latter, high-resolution spectroscopy is critical. Therefore, IGRINS appears to be an ideal instrument to study them. An IGRINS survey of these new highly-obscured massive X-ray binaries can give us a rare opportunity to carry out population analyses for understanding the evolution of massive binary systems and formation of compact objects and their mass ranges. In this talk, we will present a sample near-infrared high resolution spectra of HMXB, IGR J19140+0951 and discuss about its spectral feature. These spectra are obtained on 13th July, 2014 from IGRINS commissioning run at McDonald 2.7m telescope. And at final, we will introduce the upgrade plan of IGRINS Operation Software (IGOS), to gather the input from IGRINS observer.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.11
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• pp.2866-2874
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• 2000

This paper is concerned with the optimum design for external reinforcement of a nuclear reactor pressure vessel(RPV) in a severe accident. During the severe reactor accident of molten core, the temperature and the pressure in the nuclear reactor rise to a certain level depending on the initial and subsequent condition of a severs accident. The reis of the temperature and the internal pressure cause deterioration of the load carrying capacity and could cause failure of the RPV lower head. The deterioration of failure can be mitigated by the external cooling or the reinforcement of the lower head with additional structures. While the external cooling forces the temperature of an RPV to drop to the desired level, the reinforcement of the lower head can attain both the increase of the load carrying capacity and the temperature drop. The reinforcement of the lower head can be optimized to have the maximum effect on the collapse pressure and the temperature at the inner wall. Optimization results are compared to both the result without the reinforcement and the result with the designated reinforcement.

• Fire Science and Engineering
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• v.29 no.6
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• pp.84-90
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• 2015

Multi-layered material (sandwich panel) consists of double-sided steel plate which is incombustible material or similar material and core material which is not incombustible material. In case of sandwich panel which uses combustible material as insulation, flames spread inside the steel plate at the time of fire so that it is difficult to extinguish fire from the outside and flames spread rapidly and may cause the building to collapse. The current Building Act requires the sandwich panel to secure fire-retardant performance according to the purpose and size of building. In this study, the fire spreading prevention structure applied to partial exterior walls was applied to multi-layered material and its effect was measured through full scale fire test and the possibility to secure fire safety of buildings by applying the fire spreading prevention structure to multi-layered material in future was presented.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.139-143
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• 2015

We describe a survey of nearby core-collapse supernova (SN) explosion sites using integral field spectroscopy (IFS) techniques, which is an extension of the work described in Kuncarayakti et al. (2013). The project aims to constrain SN progenitor properties based on the study of the immediate environment of the SN. The stellar populations present at the SN explosion sites are studied by means of integral field spectroscopy, which enables the acquisition of both spatial and spectral information of the object simultaneously. The spectrum of the SN parent stellar population gives an estimate of its age and metallicity. With this information, the initial mass and metallicity of the once coeval SN progenitor star are derived. While the survey is mostly done in optical, the additional utilization of near-infrared integral field spectroscopy assisted with adaptive optics (AO) enables us to examine the explosion sites in high spatial detail, down to a few parsecs. This work is being carried out using multiple 2-8 m class telescopes equipped with integral field spectrographs in Chile and Hawaii.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.57.2-57.2
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• 2011

Recent studies find that some early-type galaxies host Type II or Ibc supernovae (SNe II, Ibc). This may imply recent star formation activities in these SNe host galaxies, but a massive star origin of the SNe Ib so far observed in early-type galaxies has been questioned because of their intrinsic faintness and unusually strong Ca lines shown in the nebular phase. To address the issue, we investigate the properties of early-type SNe host galaxies using the data with Galaxy Evolution Explorer (GALEX) ultraviolet photometry and the Sloan Digital Sky Survey optical data. Our sample includes eight SNe II and one peculiar SN Ib (SN 2000ds) host galaxies as well as 32 SN Ia host galaxies. The host galaxy of SN 2005cz, another peculiar SN Ib, is also analyzed using the GALEX data and the NASA/IPAC Extragalactic Database optical data. We find that the NUV?optical colors of SN II/Ib host galaxies are systematically bluer than those of SN Ia host galaxies, and some SN II/Ib host galaxies with NUV - r colors markedly bluer than the others exhibit strong radio emission. We perform a stellar population synthesis analysis and find a clear signature of recent star formation activities in most of the SN II/Ib host galaxies. Our results generally support the association of the SNe II/Ib hosted in early-type galaxies with core collapse of massive stars. We briefly discuss implications for the progenitors of the peculiar SNe Ib 2000ds and 2005cz.

• Journal of the Korean Institute of Gas
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• v.21 no.3
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• pp.26-32
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• 2017

Outer tank concretes of LNG storage tank are composed of prestressed concrete structures that act as a protective wall. The danger such as the collapse of structures will exist if concrete structures is not secured due to the deterioration. Concrete compressive strength directly related to the safety of structures can be predicted by using estimation equation of compressive strength through rebound hardness test and ultrasonic wave velocity method. But, there is no the estimation equation of LNG storage tank for a relation between NDT data and real strength. In this study, to obtain more accurate real strengths for LNG storage tank, core specimens were sampled from walls of pilot LNG storage tank. The rebound hardness test of general NDT for concrete structures was carried out at each 3 positions for the four areas. The compressive strength estimation equation of LNG storage tank was developed by using the data for rebound hardness test of pilot LNG storage tank and compressive strength test of sampled concrete cores.

• Analyses & Alternatives
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• v.2 no.2
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• pp.93-110
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• 2018

Due to its speciality, Johannesburg has drawn wide attention from the international academia, which the existing urban theory cannot easily explain. This paper focuses on the spatial pattern of Johannesburg, and finds that it is highly fragmented: first North-South Division due to apartheid and gold mining, secondly, the continuous sprawl due to population densification, and thirdly formation of city-region due to the fill-in spatial policy. The fragmented spatial pattern undermines the social integration and weakens the potential economic sustainability, which make the balanced multi-core spatial pattern inevitable under the influence of the international planning thought. The Johannesburg's spatial transformation comes not only from social integration, but also from the development vison of world-class status of an African city. In reality, since the collapse of apartheid, the municipal government has released series of strategic planning in different executive phase. These different plannings unanimously focus on the world class status although since 2008, the social inclusiveness is more emphasized. Thus, Johannesburg implements some spatial policies, as promoting the corridor of freedom, identifying the key nodes in the city then developing with high density, implementing the in-filling policy, managing the urban growth boundary, effectively preserving the natural system. However, the industrial structure in Johannesburg is already quite high-ended which cannot produce many jobs and also require much investment in advanced infrastructure. Thus, the strategic goals of world-class status of an African city and social inclusiveness which really need widely shared public services to some extent are in tension. After evaluation, we can see that spatial transformation is quite limited. Obviously spatial transformation largely depends on the social-economy. The population is still in flow. In this sense Johannesburg must energetically support the employment-based industry, effectively control the spatial sprawl and carry out institutional innovation which further incentive investment, gradually build an integrated regional governance. In general, how Johannesburg combines globalization and its own condition is still worth thinking in both theory and practice.