611 research outputs found
低出力パルス超音波は、脳由来神経栄養因子の発現を促進し、ラットの坐骨神経圧挫損傷後の組織的及び機能的な改善を促す
京都大学新制・課程博士博士(人間健康科学)甲第23426号人健博第93号新制||人健||6(附属図書館)京都大学大学院医学研究科人間健康科学系専攻(主査)教授 山田 重人, 教授 林 悠, 教授 森本 尚樹学位規則第4条第1項該当Doctor of Human Health SciencesKyoto UniversityDFA
Biomass gasification for syngas and biochar co-production: Energy application and economic evaluation
Syngas and biochar are two main products from biomass gasification. To facilitate the optimization of the energy efficiency and economic viability of gasification systems, a comprehensive fixed-bed gasification model has been developed to predict the product rate and quality of both biochar and syngas. A coupled transient representative particle and fix-bed model was developed to describe the entire fixed-bed in the flow direction of primary air. A three-region approach has been incorporated into the model, which divided the reactor into three regions in terms of different fluid velocity profiles, i.e. natural convection region, mixed convection region, and forced convection region, respectively. The model could provide accurate predictions against experimental data with a deviation generally smaller than 10%. The model is applicable for efficient analysis of fixed-bed biomass gasification under variable operating conditions, such as equivalence ratio, moisture content of feedstock, and air inlet location. The optimal equivalence ratio was found to be 0.25 for maximizing the economic benefits of the gasification process
Nucleosynthetic Analysis of Three-Dimensional Core-Collapse Supernova Simulations
We study in detail the ejecta conditions and theoretical nucleosynthetic
results for 18 three-dimensional core-collapse supernova (CCSN) simulations
done by F{\sc ornax}. {Most simulations are carried out to at least 3 seconds
after bounce, which allows us to follow their longer-term behaviors.} We find
that multi-dimensional effects introduce many complexities into ejecta
conditions. We see stochastic electron fraction evolution, complex peak
temperature distributions and histories, and long-tail distributions of the
time spent within nucleosynthetic temperature ranges. These all lead to
substantial variation in CCSN nucleosynthetic yields and differences with 1D
results. We discuss the production of lighter -nuclei, radioactive
isotopes, heavier elements, and a few isotopes of special interest. Comparing
pre-CCSN and CCSN contributions, we find that a significant fraction of
elements between roughly Si and Ge are generically produced in CCSNe. We find
that Ti exhibits an extended production timescale compared to Ni,
which may explain its different distribution and higher than previously
predicted abundances in supernova remnants such as Cas A and SN1987A. We also
discuss the morphology of the ejected elements. This study highlights the
high-level diversity of ejecta conditions and nucleosynthetic results in 3D
CCSN simulations and emphasizes the need for additional long-term {(10
seconds)} 3D simulations to properly address such complexities.Comment: 33 pages, 20 figures. Accepted to ApJ. Tracer data, progenitor
profiles, and ejecta nucleosynthetic abundances are available at
https://doi.org/10.5281/zenodo.1049861
Neutrino-Driven Winds in Three-Dimensional Core-Collapse Supernova Simulations
In this paper, we analyze the neutrino-driven winds that emerge in twelve
unprecedentedly long-duration 3D core-collapse supernova simulations done using
the code Fornax. The twelve models cover progenitors with ZAMS mass between 9
and 60 solar masses. In all our models, we see transonic outflows that are at
least two times as fast as the surrounding ejecta and that originate
generically from a PNS surface atmosphere that is turbulent and rotating. We
find that winds are common features of 3D simulations, even if there is
anisotropic early fallback. We find that the basic dynamical properties of 3D
winds behave qualitatively similarly to those inferred in the past using
simpler 1D models, but that the shape of the emergent wind can be deformed,
very aspherical, and channeled by its environment. The thermal properties of
winds for less massive progenitors very approximately recapitulate the 1D
stationary solutions, while for more massive progenitors they deviate
significantly due to aspherical fallback. The temporal evolution in winds
is stochastic, and there can be some neutron-rich phases. Though no strong
r-process is seen in any model, a weak r-process can be produced and isotopes
up to Zr are synthesized in some models. Finally, we find that there is
at most a few percent of a solar mass in the integrated wind component, while
the energy carried by the wind itself can be as much as 10-20% of the total
explosion energy.Comment: 21 pages, 13 figures. Accepted by the Astrophysical Journa
Towards Principled Task Grouping for Multi-Task Learning
This paper presents a novel approach to task grouping in Multitask Learning
(MTL), advancing beyond existing methods by addressing key theoretical and
practical limitations. Unlike prior studies, our approach offers a more
theoretically grounded method that does not rely on restrictive assumptions for
constructing transfer gains. We also propose a flexible mathematical
programming formulation which can accommodate a wide spectrum of resource
constraints, thus enhancing its versatility. Experimental results across
diverse domains, including computer vision datasets, combinatorial optimization
benchmarks and time series tasks, demonstrate the superiority of our method
over extensive baselines, validating its effectiveness and general
applicability in MTL
Black-Hole Formation Accompanied by the Supernova Explosion of a 40-M Progenitor Star
We have simulated the collapse and evolution of the core of a
solar-metallicity 40-M star and find that it explodes vigorously by
the neutrino mechanism. This despite its very high "compactness". Within
1.5 seconds of explosion, a black hole forms. The explosion is very
asymmetrical and has a total explosion energy of 1.610
ergs. At black hole formation, its baryon mass is 2.434 M and
gravitational mass is 2.286 M. Seven seconds after black hole
formation an additional 0.2 M is accreted, leaving a black hole
baryon mass of 2.63 M. A disk forms around the proto-neutron
star, from which a pair of neutrino-driven jets emanates. These jets accelerate
some of the matter up to speeds of 45,000 km s and contain matter
with entropies of 50. The large spatial asymmetry in the explosion
results in a residual black hole recoil speed of 1000 km s. This
novel black-hole formation channel now joins the other black-hole formation
channel between 12 and 15 M discovered previously and
implies that the black-hole/neutron-star birth ratio for solar-metallicity
stars could be 20\%. However, one channel leaves black holes in perhaps
the 5-15 M range with low kick speeds, while the other leaves
black holes in perhaps the 2.5-3.0 M mass range with high kick
speeds. However, even 8.8 seconds after core bounce the newly-formed
black hole is still accreting at a rate of 210 M
s and whether the black hole eventually achieves a significantly larger
mass over time is yet to be determined.Comment: 23 pages, 15 figures. Accepted to the Astrophysical Journa
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