Japan Coast Guard Academy

Kure, Japan

Japan Coast Guard Academy

Kure, Japan
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Fujita M.,Japan Coast Guard Academy | Itoh M.,Shinshu University | Mitani H.,Shinshu University | Sangeeta S.,Bhabha Atomic Research Center | Tyagi M.,Bhabha Atomic Research Center
Physica Status Solidi (B) Basic Research | Year: 2010

Polarized reflectivity spectra of PbMoO4 crystals have been measured using synchrotron radiation up to 20 eV. The optical constants for the crystallographic axes are derived by using a Kramers-Kronig analysis. It is found that the exciton band at 3.6 eV shows a doublet structure with distinct dichroism. X-ray photoemission spectroscopy (XPS) and the calculation of the electronic structure by a discrete variational Xα method are also carried out. The calculation shows that the valence band and the conduction band are mainly composed of the O 2p and Mo 4d states, respectively, and the Pb state contributes appreciably to the top of the valence band and the bottom of the conduction band. The valence-band XPS spectrum of PbMoO4 is compared with that of PbWO4, which reveals a remarkable difference between them. This difference reflects different magnitudes of hybridization of Mo 4d or W 5d state to the valence band. The exciton transition is explained in terms of the cationic Pb 6s → 6p excitation model taking into account the crystal-field splitting and the spin-orbit interaction of Pb 6p state. From a comparison of the doublet structure of the exciton band of PbMoO4 and PbWO4, it is suggested that the electron-hole exchange interaction plays an important role for the exciton transitions in both materials. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Kawamura N.,Japan Coast Guard Academy | Ishikawa N.,Kyoto University | Torii M.,Okayama University of Science
Geochemistry, Geophysics, Geosystems | Year: 2012

In order to reveal the potential effects of early diagenesis on magnetic minerals in deep-sea sediments, we studied early diagenetic zones and magnetic mineral characteristics of Lower Pliocene hemipelagic sediment samples from IODP Sites U1305, U1306, and U1307 on Eirik Drift, Labrador Sea. All samples analyzed were unlithified silty clay sediments recovered by a piston corer from depths down to 200 meters composite depth (mcd). Based on shipboard interstitial-water geochemistry, we divided the sediment column from each site into six early diagenetic zones. Magnetite (Fe 3O 4) was present at all analyzed depths, whereas maghemite (Fe 2O 3) was found only above the iron reduction zone. We attribute this to associated changes in interstitial redox conditions, which induced preferential dissolution of maghemitized surfaces on magnetite grains. Mineral magnetic results indicate a general down-hole change in mean grain size of magnetic minerals. At Site U1307, which has relatively low organic carbon contents, the diagenetic zones occur at greater depths than at the other studies sites. This suggests that interstitial oxygen levels at this site remained high enough to degrade organic matter through oxic bacterial activity, and that detrital magnetic minerals have been preserved even at depth. © 2012. American Geophysical Union. All Rights Reserved.


Iwanaga S.,Japan Coast Guard Academy | Namatame A.,Japan National Defense Academy
Mobile Networks and Applications | Year: 2016

In this paper, we deal with evacuation decision making of people in the disaster area. By threshold model, we discuss whether all agents decide to evacuate or not. It is reported that not all people in the affected area evacuated during the Great East Japan Earthquake. But, many evacuation simulations treat that all people evacuate. In the previous work, on the assumption that all people decide to evacuate, we dealt with the needed time to make all people evacuate if psychological conditions exist at the time of disaster. In this paper, we deal with the condition that not all people decide to evacuate and focus on contagion of evacuation decision making on real map. We found that for contagion of evacuation decision making, local neighborhood and connection of sub network is necessary. © 2016 Springer Science+Business Media New York


Iwanaga S.,Japan Coast Guard Academy | Namatame A.,Japan National Defense Academy
New Mathematics and Natural Computation | Year: 2015

There are growing interests for studying collective behavior including the dynamics of markets, the emergence of social norms and conventions and collective phenomena in daily life such as traffic congestion. In our previous work [Iwanaga and Namatame, Collective behavior and diverse social network, International Journal of Advancements in Computing Technology4(22) (2012) 321-320], we showed that collective behavior in cooperative relationships is affected in the structure of the social network, the initial collective behavior and diversity of payoff parameter. In this paper, we focus on scale-free network and investigate the effect of number of interactions on collective behavior. And we found that choices of hub agents determine collective behavior. © 2015 World Scientific Publishing Company.


Kinjo S.,Japan Coast Guard Academy | Ohno S.,Hiroshima University
IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences | Year: 2015

In this paper, we propose a zero-forcing (ZF) Tomlinson-Harashima precoding (THP) with substream permutations based on the bit rate maximization for single-user MIMO (SU-MIMO) systems. We study the effect of substream permutations on the ZF-THP SU-MIMO systems, when the mean squared error (MSE) and the bit rate are adopted for the selection of the permutation matrix as criteria. Based on our analysis, we propose a method to increase the bit rate by substream permutations, and derive QR and Cholesky decomposition-based algorithms which realize the proposed method. Furthermore, to improve the error rate performance, we apply zero transmission to subchannels with low signal-to-noise ratios. Numerical examples are provided to demonstrate the effectiveness of the proposed THP MIMO system. Copyright © 2015 The Institute of Electronics, Information and Communication Engineers.


Fujita M.,Japan Coast Guard Academy | Itoh M.,Shinshu University
Physica Status Solidi (B) Basic Research | Year: 2010

The fundamental absorption tail of PbMoO4 crystals has been investigated in the ac plane in a wide temperature range between 6 and 300K by using linearly polarized light. A remarkable dichroism between E//a and E//c is observed in the tail region. A defect-related absorption band is clarified for the polarization E//a. It is found that the Urbach rule holds for the absorption spectra measured with light polarized with E//c. The results of the analysis of the Urbach tail are discussed in comparison with the experimental results on the exciton transition and luminescence properties in this material. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Iwanaga S.,Japan Coast Guard Academy | Matsuura Y.,Japan Coast Guard Academy
Communications in Computer and Information Science | Year: 2014

The Great East Japan Earthquake occurred at 14:46 JST on Friday, March 11, 2011. It was the most powerful earthquake to have hit Japan and was one of the five most powerful earthquakes in the world since modern recordkeeping began in 1900. The earthquake triggered an extremely destructive tsunami with waves of up to 40.5 m in height. In this paper, in preparation for a possible Nankai Trough earthquake, we created a multi-agent tsunami evacuation simulation in Kure city to analyze the evacuation process and determine solutions to any problems. More specifically, we focus on the psychological conditions of people in the disaster area. During times of emergency, it is said that people fall into a psychological condition where they fail to evacuate. Based on the simulation results, we can confirm that people under psychological conditions require more time to evacuate than those in a normal frame of mind. Thus, people need to know more about psychological conditions during times of disaster to evacuate safely and efficiently. © Springer International Publishing Switzerland 2014.


Maeda Y.,Japan Coast Guard Academy
71st World Foundry Congress: Advanced Sustainable Foundry, WFC 2014 | Year: 2014

The demand on speedup of calculation and the analytical accuracy for the casting CAE become stronger to carry out the optimization of the casting system plan and a quick product design. The two technologies have been introduced to the casting CAE software and applied to simulate the mold filling behavior. One is the application of the porous-media (PM) grid. The finite difference method (FDM) using a staggered grid of Cartesian coordinate system is often used for the mold filling simulation. The shape expression precision is not very good so that the slopes and the curved surfaces of casting are replaced to stair-step shape. Then, the PM grid has enough shape expression and analytical accuracy by two parameters of control volume. The other is the use of two-phase flow analysis Multiinterface Advection and Reconstruction Solver (MARS) method in gas-liquid interface. The MARS method is possible to highly capture accuracy of the interface shape and it has also an accurate estimation of the quantity of advection. By introducing two technologies, it is possible to execute the mold filling simulation with high-speed and high accuracy. Copyright 2014 World Foundry Organization.


Iwanaga S.,Japan Coast Guard Academy | Namatame A.,Japan Coast Guard Academy
International Journal of Advancements in Computing Technology | Year: 2012

There are growing interests for studying collective behavior including the dynamics of markets, the emergence of social norms and conventions, and collective phenomena in daily life such as traffic congestion. In this paper, we deal with collective behavior in population of several social networks. We showed that collective behavior in cooperative relationships is affected in the structure of the social network and the initial collective behavior. At first, we found that collective behavior is affected by mediation coefficient but dimension of social network. In one-dimensional network, all agents come to choose the same choice and the choice is stochastically whereas it decides deterministically. This is when mediation coefficient is 0.0. Next, we found that collective behavior is affected by clustering coefficient but topology of social network. The collective behavior is far from threshold model in random network and scale-free network whereas the decision rule is same. This is when standardized clustering coefficient is low.


Kinjo S.,Japan Coast Guard Academy
IEEE Asia-Pacific Conference on Circuits and Systems, Proceedings, APCCAS | Year: 2015

Wireless communication systems based on the Tomlinson-Harashima precoding (THP) suffer from modulo operation error in noisy environments. The error leads to a fatal performance degradation when soft-input forward error correction is used because the conventional soft demapper provides erroneous log-likelihood ratio (LLR). In this paper, we propose a low complexity soft demapping method for expanded M-QAM constellations for the THP systems. We apply the conventional fast demapping procedure to the expanded M-QAM constellations, and show that the computational complexity of the developed demapper is successfully reduced. Computer simulations are given to show the effectiveness of the proposed demapper. © 2014 IEEE.

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