Effects of Sediment Supply on Low-Flow Channel Formation

Sediment Transport and Morphodynamic

A Setup Method of Tide Level Variations at Open Boundary in Estuaries for Numerical Tidal Flow Analysis

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

Horikawa Sen-Nin Chosatai(HSC) (Horikawa River Thousand-Citizen Survey Network 2010)

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

MgII Absorption Lines in z=2.974 Damped Lyman-alpha System toward Gravitationally Lensed QSO APM 08279+5255: Detection of Small-scale Structure in MgII Absorbing Clouds

1.02-1.16 micron spectra (R ~ 7,000) of the gravitationally lensed QSO APM 08279+5255 at z_em=3.911 were obtained during the commissioning run of IRCS, the 1-5 micron near-infrared camera and spectrograph for the Subaru 8.2 m Telescope. Strong MgII doublet at 2976,2800 angstrom and FeII (2600 angstrom), FeII (2587 angstrom) absorption lines at z_abs=2.974 were clearly detected in the rest-frame UV spectra, confirming the presence of a damped Lyman-alpha system at the redshift as suggested by Petitjean et al. Also MgI (2853 angstrom) absorption line is probably detected. An analysis of the absorption lines including velocity decomposition was performed. This is a first detailed study of MgII absorption system at high redshift (z > 2.5) where the MgII doublet shifts into the near-infrared in the observer's frame. The spectra of the lensed QSO pair A and B with 0.38 arcsec separation were resolved in some exposure frames under excellent seeing condition. We extracted the MgII doublet spectra of A and B separately. Although three velocity components (v ~ -28, +5, +45 km/s) are known to exist in this MgII system (Petitjean et al.), the v ~ +45 km/s absorption line was not detected toward source B, showing that the +45 km/s MgII cloud lies only in the line of sight to the source A. Our results suggests that the size of the MgII absorbing clouds is as small as 200 pc, which corresponds to the separation of A and B at the redshift of the absorber. This is the first direct detection of the small-scale structure of MgII clouds at high-redshift, confirming the estimated cloud sizes from photoionization model by Churchill and Charlton.Comment: ApJ in press (Vol.569, 20 April 2002 issue

Infrared Spectroscopy of CO Ro-vibrational Absorption Lines toward the Obscured AGN IRAS 08572+3915

We present high-resolution spectroscopy of gaseous CO absorption in the fundamental ro-vibrational band toward the heavily obscured active galactic nucleus (AGN) IRAS 08572+3915. We have detected absorption lines up to highly excited rotational levels (J<=17). The velocity profiles reveal three distinct components, the strongest and broadest (delta_v > 200 km s-1) of which is due to blueshifted (-160 km s-1) gas at a temperature of ~ 270 K absorbing at velocities as high as -400 km s-1. A much weaker but even warmer (~ 700 K) component, which is highly redshifted (+100 km s-1), is also detected, in addition to a cold (~ 20 K) component centered at the systemic velocity of the galaxy. On the assumption of local thermodynamic equilibrium, the column density of CO in the 270 K component is NCO ~ 4.5 x 10^18 cm-2, which in fully molecular gas corresponds to a H2 column density of NH2 ~ 2.5 x 10^22 cm-2. The thermal excitation of CO up to the observed high rotational levels requires a density greater than nc(H2) > 2 x 10^7 cm-3, implying that the thickness of the warm absorbing layer is extremely small (delta_d < 4 x 10-2 pc) even if it is highly clumped. The large column densities and high radial velocities associated with these warm components, as well as their temperatures, indicate that they originate in molecular clouds near the central engine of the AGN.Comment: 13 pages, 7 figures, accepted for publication in PASJ (Vol.65 No.1 2013/02/25

Low-Waterway Variation Due to Change of Water and Sediment Supply Conditions

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

Step length formula of bed-load sediment and its application to dune-bed

Proceedings of the Seventh International Conference on Hydroscience and Engineering, Philadelphia, PA, September 2006. http://hdl.handle.net/1860/732A stochastic sediment transport model consists of a pick-up rate and a step length of sediment particles. Einstein (1950) assumed that the mean step length of uniform bed-load sediment particle is approximately 100 times of its diameter. After that, some estimation methods and formulas have been presented. As for graded sediments, Nakagawa et al. (1982b) found that the mean step length of each particle is approximately 10-30 times of its diameter. Almost all of the previous works for step length have been conducted for coarse particles on flat beds. Therefore, step lengths for fine particles and non-flat bed have been not always discussed. Since the particle diameter and status of bed influence to the grain-size Reynolds number and variation coefficient of velocity, we propose the mean step length formula which considers these two parameters. The proposed step length formula is applied to sediments on flat bed and dune-bed, and is verified with the direct and indirect measurement values

Observing Dynamic State of River-Mouth Bar and its Control in the Yuragawa River

Sediment Transport and Morphodynamic