• 천문학회보
• /
• 제46권1호
• /
• pp.53.1-53.1
• /
• 2021

Dwarf galaxies are the most abundant objects in the universe. Hence, understanding the dwarfs is important but relatively little is known due to the lack of computing power and limitations in the telescope resolution. We thus use the state-of-the-art NewHorizon simulation, which is a set of cosmological hydrodynamical simulations, to dissect the quenching mechanism working on dwarf galaxies by inspecting the star formation and mass history of individual galaxies. It is known that internal (AGN, SN, stellar feedback) and external (major and minor mergers, ram pressure stripping, strangulation) mechanisms affect the quenching of dwarfs. Because of the combination of these mechanisms, periodicity in the star formation history of the dwarf galaxies is expected. To check for their periodicity, Fourier transform was performed on the star formation history. By comparing the physical timescales and the periodicity, we determine the dominant effect working on the dwarfs. Then, we compare the dominant effects working on the galaxies according to their varying properties.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2000년도 추계 학술대회논문집
• /
• pp.141-148
• /
• 2000

The discrete noise of the cross-flow fan with uniform/random pitch blades is predicted by computational methods. With the time dependent surface pressure data obtained by solving the Wavier-Stokes equation, the acoustic pressure is calculated by the Ffowcs Williams-Hawkings equation. The positions of the blade noise source are identified through investigation of the acoustic pressure history induced by one blade, and it is confirmed that the dominant noise source is near the stabilizer. Since the acoustic pressure of the random pitch fan fluctuates according to blade passing, the dominant BPF noise for the uniform pitch fan is modified into some reduced discrete noises which have a 50Hz difference from BPF.

• 한국해양공학회지
• /
• 제23권6호
• /
• pp.17-22
• /
• 2009

This study presents an investigation of the characteristics of piezoelectric sensors whose main utilization is to measure impact pressure. The piezoelectric sensors were tested from several points of view. Their characteristics were investigated for repeatability, the effect of the diameter, temperature effect, water purity, flush mounting, and AC and DC coupling. Out of these, it was revealed that the temperature effect is very significant. The characteristics of the AC and DC coupling are also very important in understanding the time history of the impact pressure.

• 설비공학논문집
• /
• 제13권7호
• /
• pp.621-626
• /
• 2001

The flow induced noise of the cross-flow fan with uniform/random pitch blades is predicted by computational methods. With the time dependent surface pressure data obtained by solving the incompressible Navier-Stokes equations in moving coordinates, the acoustic pressure is predicted by the Ffowcs Williams-Hawkings equation. The positions of the blade noise source are identified through an investigation of the acoustic pressure history induced by one blade, and it is confirmed that the dominant noise source is near the stabilizer. Since the acoustic pressure of the random pitch fan fluctuates according to the blade passin, the dominant BPF noise of the uniform pitch fan is modulated into some reduced discrete noises which have multiples of a 50Hz difference from BPF.

• 대한기계학회논문집
• /
• 제19권8호
• /
• pp.1989-1998
• /
• 1995

Characteristics of the flame propagation for normal and abnormal combustion in hydrogen premixture in a cylindrical constant-volume combustion chamber are studied numerically. A detailed hydrogen oxidation kinetic mechanism, mixture transport properties and a model describing spark ignition process are used. The calculated pressure-time history of the stable deflagration wave propagation agrees well with the experiment. The ignition of the premixture in the unburned gas, initiated by the hot spot, causes a transition from deflagration to detonation under some initial temperature and pressure. Under the initial conditions with high temperature and pressure, excessive ignition energy initiates a strong blast wave and a detonation wave that follows. The chemical reaction in the detonation wave is much more vigorous than that in the deflagration wave and the peak pressure in the detonation wave is much higher than the equilibrium value.

• Advances in aircraft and spacecraft science
• /
• 제4권4호
• /
• pp.437-448
• /
• 2017

The problem of flow through the vent is formulated as an unsteady, nonlinear, ordinary differential equation and solved using Runge-Kutta method to obtain pressure inside payload faring. An inverse problem for prediction of the discharge coefficient is presented employing measured internal pressure of the payload fairing during the ascent phase of a satellite launch vehicle. A controlled random search method is used to estimate the discharge coefficient from the measured transient pressure history during the ascent period of the launch vehicle. The algorithm predicts the discharge coefficient stepwise with function of Mach number. The estimated values of the discharge coefficients are in good agreement with differential pressure measured during the flight of typical satellite launch vehicle.

• 한국지진공학회:학술대회논문집
• /
• 한국지진공학회 2006년도 학술발표회 논문집
• /
• pp.89-96
• /
• 2006

Recently, many researches on the dissipation of excess pore pressure in liquefied sand grounds have been performed to evaluate post-liquefaction behaviors of structures. In this paper. centrifuge tests were performed to simulate liquefaction behaviors of prototype soil. The evaluation model of solidified layer thickness was developed to simulate non-linear variation of solidified layer thickness with time. Also, the dissipation of excess pore pressure in liquefied sand was evaluated by applying the solidification theory and the consolidation theory. The developed model gives a good estimation of the solidified layer thickness and the time history of excess pore pressure.

• 천문학회보
• /
• 제44권1호
• /
• pp.77.2-77.2
• /
• 2019

NGC 4522 is one of the best-known examples among the Virgo galaxies undergoing active ram pressure stripping. There have been a number of detailed observational and theoretical studies on this galaxy to constrain its stripping and star formation history. However, the impact of ram pressure on the multi-phased ISM, in particular molecular gas which plays an important role in star formation, is still not fully understood. NGC 4522, as a system where the extra-planar molecular gas is identified, is an ideal case to probe in depth how ram pressure affects molecular gas properties. Aiming to get more theoretical insights on the detailed stripping process of multi-phased ISM and its consequences, we have conducted simulations using the TIGRESS which could reproduce the realistic ISM under comparable conditions as NGC 4522. In this work, we compare the fraction of gas mass to stellar mass, star formation rates and gas depletion time scales of NGC 4522 with those measured from the simulations, not only inside the disk but also in the extra-planar space.

• 한국해양공학회지
• /
• 제15권4호
• /
• pp.92-100
• /
• 2001

It is very important to determine the coefficient of earth pressure at rest accurately in order to estimate the behavior of soil structure. For estimation of K/sub 0/-value depending upon the stress history of dry sand, a new type of K/sub 0/-oedeometer apparatus is devised, and the horizontal earth pressure is accurately measured. For this study, 2 types of one-cyclic K/sub 0/-Loading/unloading models have been studied experimentally using four relative densities of the sand. The results obtained in this test are as follows : K/sub on'/ the coefficient of earth pressure at - rest for virgin loading is a function of the angle of internal friction Φ' of the sand and is determined as K/sub on/=1 - 0.914 sin Φ', K/sub ou'/ the coefficient of earth pressure at rest for virgin unloading is a function of K/sub on/ and over consolidation ratio(OCR), and is determined as K/sub ou/=K/sub on/(OCR)K/sup a/. The exponent α, increases as the relative density increases. K/sub or'/ the coefficient of earth pressure at rest for virgin reloading decreases in hyperbola type as the vertical stress, σ/sub v/’, increases. And, the stress path at virgin reloading leads to the maximum prestress point, independent upon the value of the minimum unloading stress. The gradient of this curve, m/sub r/ increases as OCR increases.

• 건축역사연구
• /
• 제16권5호
• /
• pp.55-66
• /
• 2007

Through analysing on construction cases of stupa built in A.D. 7,8th, I have researched about these : constructive methods of inner soil of stupa, spatial compositions, characteristics of structures, arrangements of inner soil and etc. And cases analysed are six ; Mireuksajiseoktap(stone pagoda of Mireuksa Temple site), Gameunsajisamcheumgseoktap(three storied stone pagoda of Gameunsa Temple site), Goseonsajisamcheungseoktap(three storied stone pagoda of Goseonsa Temple site), Wolseong nawolliocheungseoktap(five storied stone pagoda in Nawonri, Wolseong), Guksagokseoktap(three storied stone pagoda in Guksa valley), Giamgokseoktap(three storied stone pagoda in Giam valley). Additionally we researched about inner soil of Sacheonwangsaji tapji(basement of stone stupa site in Sacheonwang Temple site) to speculate on composition of Synthetically, the foundation could be divided as core space and outer space. ; the former as structural function and the latter as ornamental function. And the core area could be divided again as center column space and buffer space. The relationship between core spaces and its formation are as belows; First, according to the area of foundation and scale of stone pagoda, formations of core are differed. As the scale of stone pagoda goes bigger, and the area of foundation goes larger, the structure of stone pagoda comprised by center column type and layered-core which endure upper load independently. On the contrary, as the scale of stone pagoda goes smaller, and the area of foundation goes lesser, the structure of stone pagoda tend to use only center column to endure upper part. Second, spatial composition of core area is comprised as two spaces, one which endure upper load and buffer space which absorb side pressure and upper pressure. The buffer space tend to be used in case of those structures which could not endure side pressure or have lots of joint. In some cases, it was located below the cover stone of foundation and gained upper load. And in case that have not gained pressure from side stone, the buffer space are comprised by smalle stone or roof tile to get structural supplement.