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Search Results: 1 - 10 of 1253 matches for " Takayuki Takasugi "
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The Corrosion Behavior of Ni3Al/Ni3V Two-Phase Intermetallic Compounds in Various Acidic Solutions
Gadang Priyotomo,Hideyuki Momono,Sanat Wagle,Kenji Okitsu,Akihiro Iwase,Yasuyuki Kaneno,Rokuro Nishimura,Takayuki Takasugi
International Journal of Corrosion , 2012, DOI: 10.1155/2012/626240
Abstract: The corrosion behavior of the Ni3Al/Ni3V two-phase intermetallic compounds with and without minor elements (Nb, Co, and Cr) to be composed of L12 phase (Ni3Al) and a mixed phase of L12 (Ni3Al) and D022 (Ni3V) has been investigated by using an immersion test in 0.5?kmol/m3 HCl, H2SO4, and HNO3 solutions. The surface morphology was observed before and after the immersion test by scanning electron microscope (SEM). The results were compared to those of the L12 single-phase Ni3(Si,Ti) and austenitic stainless steel type 304. In all acidic solutions, preferential dissolution of ( ) phase was found in Ni3Al/Ni3V, but no intergranular attack, whereas the attacks took place on Ni3(Si,Ti). The Ni3Al/Ni3V showed a higher corrosion resistance in HCl solution and a lower resistance in HNO3 solution than Ni3(Si,Ti) and type 304. The addition of the minor elements enhanced corrosion resistance in HNO3 solution, but not clearly in HCl and H2SO4 solutions. In HCl and H2SO4, their weight losses during the immersion test were almost the same. 1. Introduction Recently, Ni-Al-V intermetallic compounds with a two-phase microstructure of Ni3Al (L12) and Ni3V (D022) phases have been developed by Takasugi et al. [1–13] and are confirmed to exhibit a highly coherent interface between these constituent phases. They have superior mechanical properties (i.e., high creep rapture life, high hardness, low thermal expansion, and better thermal conductivity) and also have high tensile strength and fracture toughness over a broad range of temperature in comparison with those of Inconel 750, Inconel 718 and Hastelloy [1–13]. Therefore, the Ni3Al/Ni3V two-phase intermetallic compounds are a candidates as materials in land-based, marine-based, and aero-gas turbine industries (turbine blade), high strength nut and bolt, and high temperature bearing or high temperature tool [8, 9, 14]. However, many studies revealed that the intermetallic compounds containing aluminum are very susceptible to hydrogen embrittlement [15–18], where hydrogen embrittlement takes place with permeation of atomic hydrogen formed by corrosion reaction into the compounds. Hence, to suppress this environmental embrittlement a small amount of boron was added to these compounds. However, it was reported that the boron segregation at grain boundaries became the preferential dissolution site and led to the intergranular attack in the L12 single-phase Ni3(Si,Ti) [19]. Furthermore, Ni base intermetallic compounds such as single-phase Ni3(Si,Ti) have attractive properties for high-temperature structural material (e.g., high
Composite Neutrinos and Double Beta Decay
Eiichi Takasugi
Physics , 1995, DOI: 10.1143/PTP.94.1097
Abstract: Neutrinoless double beta decay $(\b\b)_{0\nu}$ occurs through the magnetic coupling of dimension five, $\lambda_W^{(\nu*)}/m_{\nu*}$, among the excited electron neutrino $\nu^*$, electron and $W$ boson if $\nu^*$ is a massive Majorana neutrino. If the coupling is not small, i.e., $\lambda_W^{(\nu*)}>1$ the mass of the excited neutrino must not be gless than the $Z$ boson mass, $m_Z$. Since $\nu^*$ contributes in the $(\b\b)_{0\nu}$ decay as a vertual state, this decay will give an oppotunity to explore the much heavier mass region of $\nu^*$. In this paper, we present the decay formula of $(\b\b)_{0\nu}$ decay through the $\nu^*$ exchange and discuss the constraint on the coupling constant and the mass of the excited neutrino. By comparing the recent data for ${}^{76}$Ge, we find $\lambda_W^{(\nu*)}({1\rm TeV}/m_{\nu*})) (m_N/{1\rm TeV})^{\frac 12}< 4.1\cdot 10^{-3}$ where $m_N$ is the Majorana mass of the excited electron neutrino. If $m_N=m_{\nu*}$ and $\lambda_W^{(\nu*)}>1$, we find the mass bound for the excited Majorana neutrino as $m_{\nu^*} > 5.9\cdot 10^4$TeV. In order to obtain the constraint on the composite scale $\Lambda$, we have to specify the model. For the mirror type and the homodoublet type models, $\lambda_W^{(\nu*)}/m_{\nu*}=f/(\sqrt 2 \Lambda)$ where $f$ is the relative strength of gauge couplings. Then, we obtain $\Lambda > 170 f (m_N/{1\rm TeV})^{\frac 12}$TeV. For the sequential type model, $\lambda/m_{\nu*}=fv/(\sqrt 2 \Lambda^2)$ where $v$ is the vacuum expectation value of the dopublet Higgs boson, i.e., $v=$250GeV. In this model, we find $\Lambda > 6.6 f^{\frac 12} (m_N/{1\rm TeV})^{\frac 14}$TeV.
The rephasing freedom and the NNI form of quark mass matrices
Eiichi Takasugi
Physics , 1997, DOI: 10.1143/PTP.98.177
Abstract: For three generations of quarks, we show that one of quark mass matrices can be transformed into either a Fritzsch form or a Branco-Silva-Marcos form, while the other is kept in the NNI basis. In these bases, quark mass matrices are determined unambiguously once quark masses and the CKM mixing are given.
Double Beta Decay Constraint on Composite Neutrinos
Eiichi Takasugi
Physics , 1997, DOI: 10.1143/PTP.98.977
Abstract: Neutrinoless double beta decay occurs through the magnetic coupling of dimension five, $\lambda_W/m_{\nu*}$, among the excited electron neutrino $\nu^*$, electron and $W$ boson if $\nu^*$ is a massive Majorana neutrino. (\lambda_W m_W / m_{\nu*}^2 |\frac{(m_*/m_W) +2}{(m_*/m_W +1)^2} -0.129{m_*/m_W} | <2.13\times 10^{-2}, where $\lambda_W$ is the relative strength, $m_{\nu*}$ is the composite scale and $m_*$ is the mass of excited neutrino. If the coupling is not small, i.e., $\lambda_W>1$ and $m_{\nu*}=m_*$, we find $m_*>3.4 m_W$.
A cost-optimal scenario of CO2 sequestration in a carbon-constrained world through to 2050  [PDF]
Takayuki Takeshita
Natural Science (NS) , 2013, DOI: 10.4236/ns.2013.52A043
Abstract:

In this paper, a regionally disaggregated global energy system model with a detailed treatment of the whole chain of CO2 capture and storage (CCS) is used to derive the cost-optimal global pattern of CO2 sequestration in regional detail over the period 2010-2050 under the target of halving global energy-related CO2 emissions in 2050 compared to the 2005 level. The major conclusions are the following. First, enhanced coalbed methane recovery will become a key early opportunity for CO2 sequestration, so coalrich regions such as the US, China, and India will play a leading role in global CO2 sequestration. Enhanced oil recovery will also have a participation in global CO2 sequestration from the initial stage of CCS deployment, which may be applied mainly in China, southeastern Asia, and West Africa in 2030 and mainly in the Middle East in 2050. Second, CO2 sequestration will be carried out in an increasing number of world regions over time. In particular, CCS will be deployed extensively in today’s developing countries. Third, an increasing amount of the captured CO2 will be stored in aquifers in many parts of the world due to their abundant and widespread availability and their low cost. It is shown that the share of aquifers in global CO2 sequestration reaches 82.0% in 2050.

Prospects for Renewable and Fossil-Based Electricity Generation in a Carbon-Constrained World  [PDF]
Takayuki Takeshita
International Journal of Clean Coal and Energy (IJCCE) , 2013, DOI: 10.4236/ijcce.2013.22B008
Abstract: In this paper, a regionally disaggregated global energy system model with a detailed treatment of the electricity supply sector is used to derive the cost-optimal choice of electricity generation technologies for each of 70 world regions over the period 2010-2050 under a constraint of halving global energy-related CO2 emissions in 2050 compared to the 2000 level. It is first shown that the long-term global electricity generation mix under the CO2 constraint becomes highly diversified, which includes coal, natural gas, nuclear, biomass, hydro, geothermal, onshore and offshore wind, solar photovoltaics (PV), and concentrated solar power (CSP). In this carbon-constrained world, 89.9% of the electricity generation from coal, natural gas, and biomass is combined with CO2 capture and storage (CCS) in 2050. It is then shown that the long-term electricity generation mix under the CO2 constraint varies significantly by world region. Fossil fuels with CCS enter the long-term electricity generation mix in all world regions. In contrast, there is a sharp regional difference in the renewable generation technology of choice in the long term. For example, the world regions suitable for PV plants include the US, Western Europe, Japan, Korea, and China, while those suitable for CSP plants include the Middle East, Africa, Australia, and western Asia. Offshore wind is deployed on a large scale in the UK, Ireland, Nordic countries, the southern part of Latin America, and Japan.
Prospects for Coalbed Methane and Shale Gas in a Carbon-Constrained World: A Preliminary Analysis  [PDF]
Takayuki Takeshita
International Journal of Clean Coal and Energy (IJCCE) , 2013, DOI: 10.4236/ijcce.2013.22B007
Abstract:

Using a regionally disaggregated global energy system model with a detailed treatment of the natural gas resource base, this paper analyzes the competitiveness of coalbed methane and shale gas in the global primary energy mix and the cost-optimal pattern of their production in regional detail over the period 2010-2050 under a constraint of halving global energy-related CO2 emissions in 2050 compared to the 2000 level. It is first shown that neither coalbed methane nor shale gas could become an important fuel in the global primary energy mix throughout the time horizon, although each of them could become an important source of world natural gas production from around 2030 onwards. It is then shown that unlike findings of previous studies, coalbed methane would be more attractive than shale gas as a primary energy source globally under the CO2 constraint used here. The results indicate that North America continues to be the world’s largest coalbed methane producer until 2030, after which China overtakes North America and retains this position until 2050. Also, India, Russia, South Africa, and Australia contribute noticeably to world coalbed methane production. The results also indicate that North America continues to dominate world shale gas production until 2040, after which a number of world regions, notably India, Europe, and China, begin to participate visibly in world shale gas production.


Application of Fast N-Body Algorithm to Option Pricing under CGMY Model  [PDF]
Takayuki Sakuma
Journal of Mathematical Finance (JMF) , 2017, DOI: 10.4236/jmf.2017.72016
Abstract: The N-body problem is an active research topic in physics for which there are two major algorithms for efficient computation, the fast multipole method and treecode, but these algorithms are not popular in financial engineering. In this article, we apply a fast N-body algorithm called the Cartesian treecode to the computation of the integral operator of integro-partial differential equations to compute option prices under the CGMY model, a generalization of a jump-diffusion model. We present numerical examples to illustrate the accuracy and effectiveness of the method and thereby demonstrate its suitability for application in financial engineering.
Neutrino Mixing based on Mass Matrices with a $2 \leftrightarrow 3$ Symmetry
Koide, Yoshio;Takasugi, Eiichi
High Energy Physics - Phenomenology , 2007, DOI: 10.1103/PhysRevD.77.016006
Abstract: Under the assumption that the $2\leftrightarrow 3$ symmetry is broken only through phases, we give a systematical investigation of possible lepton mass matrix forms without referring to the explicit parameter values. The two types of the $2\leftrightarrow 3$ symmetry are investigated: one is that the left- and right-handed fields $(f_L, f_R)$ obey the symmetry, and another one is that only $f_L$ obeys the symmetry. In latter case, in spite of no $2\leftrightarrow 3$ symmetry in the Majorana mass matrix $M_R$ for $\nu_R$, the neutrino seesaw mass matrix still obey the $2\leftrightarrow 3$ symmetry. Possible phenomenologies are discussed.
Absorption Probability of De Sitter Horizon for Massless Fields with Spin
H. Suzuki,E. Takasugi
Physics , 1995, DOI: 10.1142/S0217732396000473
Abstract: The evaluation of the absorption coefficients are important for particle emission caused by Hawking radiation. In the case of cosmological particle emission from the event horizon in De Sitter space, it is known that the scalar wave functions are solved in terms of Legendre functions. For fields with higher spin, the solution has been examined with low frequency approximation. We shows that the radial equations of the fields with spin $0,1/2,1$ and $2$ can be solved analytically in terms of the hypergeometric functions. We calculate the absorption probability using asymptotic expansion for high frequency limit. It turns out that the absorption coefficients are universal to all bosonic fields; They depend only on the angular momentum and not spin. In the case of spin $1/2$ fermions, we can also find non-vanishing absorption probability in contrast to the previously known result.
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