DIRECT NUMERICAL SIMULATION OF FLUIDIZED BED WITH IMMERSED BOUNDARY METHOD

The applicability of the immersed boundary (IB) method, which is one of direct numerical simulations (DNS) for multiphase flow analyses, has been examined to simulate a fluidized bed. The volumetric-force type IB method developed by Kajishima et al. (2001) has been applied in the present work. While particle-fluid interaction force is calculated with the surface integral of fluid stress at the interface between particle and fluid in the standard IB method, the volume integral of interaction force is used in the volumetric-force type IB method. In order to validate the present simulation code, drag force and lift force firstly were calculated with IB method. Then calculated drag coefficients were compared with values estimated with Schiller-Nauman and Ergun equations, while calculated lift coefficients were compared with the previous simulated results. The difference of drag was within approximately 1% except in the range of low Reynolds number. Thus, the accuracy of the present simulation code was confirmed. Next, simulation of fluidized bed was carried out. Since DNS requires a large computer capacity, only 400 particles were used. The particle is 1.0mm in diameter and 2650kg/m3 in density. From the simulated results, concentrated upward stream lines from the bottom wall were observed in some regions. This inhomogeneous flow would be attributed to particulate structure

Photodisintegration cross section of ⁴He in the giant dipole resonance energy region

We have performed for the first time the simultaneous measurement of the two-body and three-body photodisintegration cross sections of ⁴He in the energy range from 21.8 to 29.8 MeV using monoenergetic pulsed photons and a 4π time projection chamber containing ⁴He gas as an active target in an event-by-event mode. The photon beam was produced via the Compton backscattering of laser photons with high-energy electrons. The ⁴He(γ,p)³H and ⁴He(γ,n)³He cross sections were found to increase monotonically with energy up to 29.8 MeV, in contrast to the result of a recent theoretical calculation based on the Lorentz integral transform method that predicted a pronounced peak at around 26–27 MeV. The energy dependence of the obtained ⁴He(γ,n)³He cross section up to 26.5 MeV is marginally consistent with a Faddeev-type calculation predicting a flat pattern of the excitation function. The cross section ratio of ⁴4He(γ,p)³H to ⁴He(γ,n)³He is found to be consistent with the expected value for charge symmetry of the strong interaction within the experimental uncertainty in the measured energy range. The present results for the total and two-body cross sections of the photodisintegration of ⁴He are compared to previous experimental data and recent theoretical calculations.Murata M., Kawabata T., Adachi S., et al. Photodisintegration cross section of ⁴He in the giant dipole resonance energy region. Physical Review C 107, 21 (2023); https://doi.org/10.1103/PhysRevC.107.064317

Photodisintegration of 80Se^{80}Se as a probe of neutron capture for the s-process branch-point nucleus 79Se^{79}Se

Photoneutron cross sections were measured for 80Se near the neutron separation energy with the laser Compton scattering γ rays. The stellar neutron capture rate for 79Se was evaluated by using the photodisintegration data as constraints on the E1 γ strength function within the framework of the Hauser-Feshbach statistical model. The result is compared with the model calculation of Bao and Käppeler. © Copyright owned by the author(s).SCOPUS: cp.pinfo:eu-repo/semantics/publishe

Photo-disintegration cross section measurements on 186^{186}W, 187^{187}Re and 188^{188}Os: Implications for the Re-Os cosmochronology

Cross sections of the $^{186}$W, $^{187}$Re, $^{188}$Os($\gamma,n$) reactions were measured using quasi-monochromatic photon beams from laser Compton scattering (LCS) with average energies from 7.3 to 10.9 MeV. The results are compared with the predictions of Hauser-Feshbach statistical calculations using four different sets of input parameters. In addition, the inverse neutron capture cross sections were evaluated by constraining the model parameters, especially the $E1$ strength function, on the basis of the experimental data. The present experiment helps to further constrain the correction factor $F_{\sigma}$ for the neutron capture on the 9.75 keV state in $^{187}$Os. Implications of $F_{\sigma}$ to the Re-Os cosmochronology are discussed with a focus on the uncertainty in the estimate of the age of the Galaxy.Comment: 11 page

Subaru FOCAS Spectroscopic Observations of High-Redshift Supernovae

We present spectra of high-redshift supernovae (SNe) that were taken with the Subaru low resolution optical spectrograph, FOCAS. These SNe were found in SN surveys with Suprime-Cam on Subaru, the CFH12k camera on the Canada-France-Hawaii Telescope (CFHT), and the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope (HST). These SN surveys specifically targeted z>1 Type Ia supernovae (SNe Ia). From the spectra of 39 candidates, we obtain redshifts for 32 candidates and spectroscopically identify 7 active candidates as probable SNe Ia, including one at z=1.35, which is the most distant SN Ia to be spectroscopically confirmed with a ground-based telescope. An additional 4 candidates are identified as likely SNe Ia from the spectrophotometric properties of their host galaxies. Seven candidates are not SNe Ia, either being SNe of another type or active galactic nuclei. When SNe Ia are observed within a week of maximum light, we find that we can spectroscopically identify most of them up to z=1.1. Beyond this redshift, very few candidates were spectroscopically identified as SNe Ia. The current generation of super red-sensitive, fringe-free CCDs will push this redshift limit higher.Comment: 19 pages, 26 figures. PASJ in press. see http://www.supernova.lbl.gov/2009ClusterSurvey/ for additional information pertaining to the HST Cluster SN Surve

s -process branching at W 185 revised

The neutron capture cross section of the unstable s-process branching nucleus 185W has been derived from experimental data of the inverse 186W(g,n)185W photodisintegration taken with monochromatic photon beams from laser Compton scattering. The result of sigma = 553 +- 60 mb at kT = 30 keV leads to a relatively high effective neutron density in the classical s-process of N_n = 4.7 \times 10^8 cm^-3. A realistic model for the s-process in thermally pulsing AGB stars overestimates the abundance of 186Os significantly because of the relatively small neutron capture cross section of 185W.Comment: 10 pages, 3 figure