Evidence of grain growth in the disk of the bipolar proto-planetary nebula M 1--92

We investigate the dust size and dust shell structure of the bipolar proto-planetary nebula M 1--92 by means of radiative transfer modeling. Our models consists of a disk and bipolar lobes that are surrounded by an AGB shell, each component having different dust characteristics. The upper limit of the grain size $a_\mathrm{max}$ in the lobes is estimated to be $0.5 \mu$m from the polarization value in the bipolar lobe. The $a_\mathrm{max}$ value of the disk is constrained with the disk mass (0.2 M_{\sun}), which was estimated from a previous CO emission line observation. We find a good model with $a_\mathrm{max}=1000.0 \mu$m, which provides an approximated disk mass of 0.15 M_{\sun}. Even taking into account uncertainties such as the gas-to-dust mass ratio, a significantly larger dust of $a_\mathrm{max}>100.0 \mu$m, comparing to the dust in the lobe, is expected. We also estimated the disk inner radius, the disk outer radius, and the envelope mass to be 30 $R_\star$(=9 AU), 4500 AU, and 4 M_{\sun}, respectively, where $v_\mathrm{exp}$ is the expansion velocity. If the dust existing in the lobes in large separations from the central star undergoes little dust processing, the dust sizes preserves the ones in the dust formation. Submicron-sized grains are found in many objects besides M 1--92, suggesting that the size does not depend much on the object properties, such as initial mass of the central star and chemical composition of the stellar system. On the other hand, the grain sizes in the disk do. Evidence of large grains has been reported in many bipolar PPNs, including M 1--92. This result suggests that disks play an important role in grain growth.Comment: 8 pages with 3 figures. Accepted for publication in A&

Magnetic digital flop of ferroelectric domain with fixed spin chirality in a triangular lattice helimagnet

Ferroelectric properties in magnetic fields of varying magnitude and direction have been investigated for a triangular-lattice helimagnet CuFe1-xGaxO2 (x=0.035). The magnetoelectric phase diagrams were deduced for magnetic fields along [001], [110], and [1-10] direction, and the in-plane magnetic field was found to induce the rearrangement of six possible multiferroic domains. Upon every 60-degree rotation of in-plane magnetic field around the c-axis, unique 120-degree flop of electric polarization occurs as a result of the switch of helical magnetic q-vector. The chirality of spin helix is always conserved upon the q-flop. The possible origin is discussed in the light of the stable structure of multiferroic domain wall.Comment: 5 pages, 4 figures. Accepted in Phys. Rev. Let

Development of a Practical Straightening Simulation for Welded Structures Using Inherent Strain Method

Welding is the most widely used assembly method available to industries in the construction of metal structures, ships, and offshore platforms. However, this method always produces a certain amount of distortion that will not only degrade the performance but also increase the building cost of the structure, and it should be straightened. Murakawa [1] developed a thermal elastic plastic based and inherent strain based welding simulation FE code JWRIAN. Coarse shell FE models are usually used in the inherent strain based JWRIAN elastic analyses. This drastically reduces the manpower needed for modeling and computer resources needed for the calculation. However, it is not easy to perform straightening analysis using JWRIAN because gas heating’s inherent strain distributes over a range much smaller than element sizes of the shell model.RUIZ [2] modified JWRIAN’s code so that the inherent strain equivalent nodal forces along the heating line are calculated and applied in the elastic shell analysis. However, a discrepancy between 3-dimensional thermal-elastic-plastic analysis and elastic analysis was observed. This is mainly because of the nature of solid and shell elements. RUIZ [3] proposed a linearized inherent strain and applied it to both 3-d and 2d analysis, getting matching results between solid and shell element models. In this study, as a working example, a thin plate panel with an opening is considered utilizing the developed system at the same time a friendly user interface for staffs and workers on a production site is developed.  Keywords: Inherent strain, straightening, finite element method, Gauss-Legendre quadratur

Ferroelectricity induced by spin-dependent metal-ligand hybridization in Ba2_2CoGe2_2O7_7

We have investigated the variation of induced ferroelectric polarization under magnetic field with various directions and magnitudes in a staggered antiferromagnet Ba$_2$CoGe$_2$O$_7$. While the ferroelectric polarization cannot be explained by the well-accepted spin current model nor exchange striction mechanism, we have shown that it is induced by the spin-dependent $p$-$d$ hybridization between the transition-metal (Co) and ligand (O) via the spin-orbit interaction. On the basis of the correspondence between the direction of electric polarization and the magnetic state, we have also demonstrated the electrical control of the magnetization direction.Comment: 4 pages, 4 figure

Mass Incarceration Is Dead, Long Live the Carceral State!

Reviewing: James Forman, Jr. - Locking Up Our Own: Crime and Punishment in Black America; Issa Kohler-Hausmann - Misdemeanorland: Criminal Courts and Social Control in an Age of Broken Windows Policing; Heather Schoenfeld - Building the Prison State: Race and the Politics of Mass Incarceratio

直並列接続された電力変換器に対する受動性に基づく制御の適用とその回路特性

付記する学位プログラム名: 京都大学卓越大学院プログラム「先端光・電子デバイス創成学」京都大学新制・課程博士博士(工学)甲第24620号工博第5126号新制||工||1980(附属図書館)京都大学大学院工学研究科電気工学専攻(主査)教授 土居 伸二, 教授 小嶋 浩嗣, 准教授 薄 良彦, 教授 引原 隆士学位規則第4条第1項該当Doctor of Philosophy (Engineering)Kyoto UniversityDFA