상용차 기반에 대한 주차보조시스템 사용자 감성 평가

전재석(Jaeseok Jeon),박현배(Hyunbae Park),문희석(Heeseok Moon),곽수진(Sujin Kwag) 한국자동차공학회 2013 한국자동차공학회 부문종합 학술대회 Vol.2013 No.5

In this paper, we described about evaluation of human sensibility using park assist system of the commercial vehicle. The perpendicular parking and parallel parking have been carried out as a user test and subjects are classified as beginning drivers, drivers with less than 1 year experience and over 3 years experience. As a result, parking duration of beginning drivers and drivers with less than 1 year experience who use automatic parking assistance system is similar to drivers with over 3 years experience. However error occurred according to sensor position and distance between vehicle and parking space. And also it occurred that the vehicle leaves from parking line or does not recognize the parking space. Therefore, if we improve its completeness by compensating problems that came up from this evaluation and distribute the automatic parking assistance system, it is expected that the park assistance system is to help driver providing convenience of parking.

THE IMPACT OF NONLINEAR STRUCTURE FORMATION ON THE POWER SPECTRUM OF TRANSVERSE MOMENTUM FLUCTUATIONS AND THE KINETIC SUNYAEV-ZEL’DOVICH EFFECT

Park (박현배), Hyunbae,Komatsu, Eiichiro,Shapiro, Paul R.,Koda, Jun,Mao, Yi American Astronomical Society 2016 The Astrophysical journal Vol.818 No.1

<P>Cosmological transverse momentum fields, whose directions are perpendicular to Fourier wave vectors, induce temperature anisotropies in the cosmic microwave background via the kinetic Sunyaev-Zel'dovich (kSZ) effect. The transverse momentum power spectrum contains the four-point function of density and velocity fields, <delta delta nu nu >. In the post-reionization epoch, nonlinear effects dominate in the power spectrum. We use perturbation theory and cosmological N-body simulations to calculate this nonlinearity. We derive the next-to-leading order expression for the power spectrum with a particular emphasis on the connected term that has been ignored in the literature. While the contribution from the connected term on small scales (k > 0.1 h Mpc(-1)) is subdominant relative to the unconnected term, we find that its contribution to the kSZ power spectrum at l = 3000 at z < 6 can be as large as ten percent of the unconnected term, which would reduce the allowed contribution from the reionization epoch (z > 6) by twenty percent. The power spectrum of transverse momentum on large scales is expected to scale as k(2) as a consequence of momentum conservation. We show that both the leading and the next-to-leading order terms satisfy this scaling. In particular, we find that both of the unconnected and connected terms are necessary to reproduce k(2).</P>

Pair-wise peculiar velocity and the redshift space distortion

Hyunbae Park,Motonari Tonegawa,Yi Zheng,Cris Sabiu,Xiao-dong Li,Changbom Park 한국천문학회 2018 天文學會報 Vol.43 No.2

THE KINETIC SUNYAEV-ZEL'DOVICH EFFECT AS A PROBE OF THE PHYSICS OF COSMIC REIONIZATION: THE EFFECT OF SELF-REGULATED REIONIZATION

Park, Hyunbae,Shapiro, Paul R.,Komatsu, Eiichiro,Iliev, Ilian T.,Ahn, Kyungjin,Mellema, Garrelt IOP Publishing 2013 The Astrophysical journal Vol.769 No.2

<P>We calculate the angular power spectrum of the cosmic microwave background temperature fluctuations induced by the kinetic Sunyaev-Zel'dovich (kSZ) effect from the epoch of reionization (EOR). We use detailed N-body+radiative-transfer simulations to follow inhomogeneous reionization of the intergalactic medium. For the first time, we take into account the 'self-regulation' of reionization: star formation in low-mass dwarf galaxies (10(8) M-circle dot less than or similar to M less than or similar to 10(9) M-circle dot) or minihalos (10(5) M-circle dot less than or similar to M less than or similar to 10(8) M-circle dot) is suppressed if these halos form in the regions that were already ionized or Lyman-Werner dissociated. Some previous work suggested that the amplitude of the kSZ power spectrum from the EOR can be described by a two-parameter family: the epoch of half-ionization and the duration of reionization. However, we argue that this picture applies only to simple forms of the reionization history which are roughly symmetric about the half-ionization epoch. In self-regulated reionization, the universe begins to be ionized early, maintains a low level of ionization for an extended period, and then finishes reionization as soon as high-mass atomically cooling halos dominate. While inclusion of self-regulation affects the amplitude of the kSZ power spectrum only modestly (similar to 10%), it can change the duration of reionization by a factor of more than two. We conclude that the simple two-parameter family does not capture the effect of a physical, yet complex, reionization history caused by self-regulation. When added to the post-reionization kSZ contribution, our prediction for the total kSZ power spectrum is below the current upper bound from the South Pole Telescope. Therefore, the current upper bound on the kSZ effect from the EOR is consistent with our understanding of the physics of reionization.</P>

Redshift Space Distortion on the Small Scale Clustering of Structure

Hyunbae Park,Cristiano Sabiu,Xiao-dong Li,Changbom Park,Juhan Kim 한국천문학회 2017 天文學會報 Vol.42 No.2

Alcock-Paczynski Test with the Evolution of Redshift-Space Galaxy Clustering Anisotropy: Understanding the Systematics

Hyunbae Park,Changbom Park,Motonari Tonegawa,Yi Zheng,Cristiano G. Sabiu,Xiao-dong Li,Sungwook E. Hong,Juhan Kim 한국천문학회 2019 天文學會報 Vol.44 No.1

GRAVITATIONAL POTENTIAL ENVIRONMENT OF GALAXIES. I. SIMULATION

Park, Hyunbae,Kim, Juhan,Park, Changbom IOP Publishing 2010 The Astrophysical journal Vol.714 No.1

<P>We extend the concept of galaxy environment from the local galaxy number density to the gravitational potential and its functions like the shear tensor. For this purpose, we examine whether or not one can make an accurate estimation of the gravitational potential from an observational sample which is finite in volume, biased due to galaxy biasing, and subject to redshift space distortion. Dark halos in a Lambda CDM simulation are used in this test. We find that one needs to stay away from the sample boundaries by more than 30 h(-1) Mpc to reduce the error within 20% of the rms values of the potential or the shear tensor. The error due to the galaxy biasing can be significantly reduced by using the galaxy mass density field instead of the galaxy number density field. The error caused by the redshift space distortion can be effectively removed by correcting galaxy positions for the peculiar velocity effects. We inspect the dependence of dark matter halo properties on four environmental parameters: local density, gravitational potential, and the ellipticity, and prolateness of the shear tensor. We find that the local density has the strongest correlation with halo properties. This is evident that the internal physical properties of dark halos are mainly controlled by small-scale physics. In high-density regions dark halos are on average more massive and spherical and have higher spin parameter and velocity dispersion. We also study the relation between the environmental parameters and the subtypes of dark halos. The spin parameter of satellite halos depends only weakly on the local density for all mass ranges studied, while that of isolated or central halos depends more sensitively on the local density. The gravitational potential and the shear tensor have weaker correlations with halo properties, but have environmental information independent of the local density.</P>

THE HYDRODYNAMIC FEEDBACK OF COSMIC REIONIZATION ON SMALL-SCALE STRUCTURES AND ITS IMPACT ON PHOTON CONSUMPTION DURING THE EPOCH OF REIONIZATION

Park(박 현배), Hyunbae,Shapiro, Paul R.,Choi, Jun-hwan,Yoshida, Naoki,Hirano, Shingo,Ahn, Kyungjin American Astronomical Society 2016 The Astrophysical journal Vol.831 No.1

<P>Density inhomogeneity in the intergalactic medium (IGM) can boost the recombination rate of ionized gas substantially, affecting the growth of H II regions during reionization. Previous attempts to quantify this effect typically failed to resolve down to the Jeans scale in the preionization IGM, which is important in establishing this effect, along with the hydrodynamical back-reaction of reionization on it. Toward that end, we perform a set of fully coupled, radiation-hydrodynamics simulations from cosmological initial conditions, extending the mass resolution of previous work to the scale of minihalos. Pre-reionization structure is evolved until a redshift z(i) at which the ionizing radiation from external sources arrives to sweep an R-type ionization front supersonically across the volume in a few million years, until it is trapped on the surfaces of minihalos and converted to D-type, after which the minihalo gas is removed by photoevaporative winds. Small-scale density structures during this time lead to a high (>10) clumping factor for ionized gas, which hugely boosts the recombination rate until the structures are disrupted by the hydrodynamic feedback after similar to 10-100. Myr. For incoming stellar radiation with intensity J(21) in a 200. h(-1). kpc box with the mean density contrastd (alpha) over bar, the number of extra recombinations per H atom, on top of what is expected from homogeneously distributed gas, is given by 0.32[J(21)](0.12) [(1 + Z(i))/11]-(1.7) [1 + (delta) over bar](2.5). In models in which most of the volume is ionized toward the end of reionization, this can add more than one recombination per H atom to the ionizing photon budget to achieve reionization.</P>

The Impact of Baryonic Physics on the Kinetic Sunyaev-Zel’dovich Effect

Park, Hyunbae,Alvarez, Marcelo A.,Bond, J. Richard American Astronomical Society 2018 The Astrophysical journal Vol.853 No.2

<P>Poorly understood 'baryonic physics' impacts our ability to predict the power spectrum of the kinetic SunyaevZel'dovich (kSZ) effect. We study this in a sample high-resolution simulation of galaxy formation and feedback, Illustris. The high resolution of Illustris allows us to probe the kSZ power spectrum on multipoles l = 10(3)-3 x 10(4). Strong AGN feedback in Illustris nearly wipes out gas fluctuations at k greater than or similar to 1hMpc(-1) and at late times, likely somewhat underpredicting the kSZ power generated at z less than or similar to 1. The post-reionization kSZ power spectrum for Illustris is well-fit byD(l)(z<6) = 1.38[l/3000](0.21) mu K-2 over 3000 less than or similar to l less than or similar to 10,000, somewhat lower than most other reported values but consistent with the analysis of Shaw et al. Our analysis of the bias of free electrons reveals subtle effects associated with the multi-phase gas physics and stellar fractions that affect even linear scales. In particular, there are fewer electrons in biased galaxies, due to gas-cooling and star formation, and this leads to an electron bias of less than one, even at low wavenumbers. The combination of bias and electron fraction that determines the overall suppression is relatively constant, f(e)(2)b(e0)(2) similar to 0.7, but more simulations are needed to see if this is Illustris-specific. By separating the kSZ power into different terms, we find that at least 6% (10%) of the signal at l = 3000 (10,000) comes from non-Gaussian connected four-point density and velocity correlations, <delta nu delta nu >(c), even without correcting for the Illustris simulation box-size. A challenge going forward will be accurately modeling long-wave velocity modes simultaneously with Illustris-like high resolution to capture the complexities of galaxy formation and its correlations with large-scale flows.</P>

Post-reionization Kinetic Sunyaev-Zel'dovich Effect in Illustris Simulation

Hyunbae Park,Cristiano Sabiu,Xiao-dong Li,Changbom Park,Juhan Kim 한국천문학회 2017 天文學會報 Vol.42 No.1