排序方式: 共有83条查询结果,搜索用时 15 毫秒
41.
Shingo Kobayashi Michikazu KobayashiYuki Kawaguchi Muneto NittaMasahito Ueda 《Nuclear Physics B》2012,856(2):577-606
Topological excitations are usually classified by the nth homotopy group πn. However, for topological excitations that coexist with vortices, there are cases in which an element of πn cannot properly describe the charge of a topological excitation due to the influence of the vortices. This is because an element of πn corresponding to the charge of a topological excitation may change when the topological excitation circumnavigates a vortex. This phenomenon is referred to as the action of π1 on πn. In this paper, we show that topological excitations coexisting with vortices are classified by the Abe homotopy group κn. The nth Abe homotopy group κn is defined as a semi-direct product of π1 and πn. In this framework, the action of π1 on πn is understood as originating from noncommutativity between π1 and πn. We show that a physical charge of a topological excitation can be described in terms of the conjugacy class of the Abe homotopy group. Moreover, the Abe homotopy group naturally describes vortex-pair creation and annihilation processes, which also influence topological excitations. We calculate the influence of vortices on topological excitations for the case in which the order parameter manifold is Sn/K, where Sn is an n-dimensional sphere and K is a discrete subgroup of SO(n+1). We show that the influence of vortices on a topological excitation exists only if n is even and K includes a nontrivial element of O(n)/SO(n). 相似文献
42.
Non-Abelian global strings are expected to form during the chiral phase transition. They have orientational zero modes in the internal space, associated with the vector-like symmetry SU(N)L+R broken in the presence of strings. The interaction among two parallel non-Abelian global strings is derived for general relative orientational zero modes, giving a non-Abelian generalization of the Magnus force. It is shown that when the orientations of the strings are the same, the repulsive force reaches the maximum, whereas when the relative orientation becomes the maximum, no force exists between the strings. For the Abelian case we find a finite volume correction to the known result. The marginal instability of the previously known Abelian η′ strings is discussed. 相似文献
43.
We show that knots of spin textures can be created in the polar phase of a spin-1 Bose-Einstein condensate, and discuss experimental schemes for their generation and probe, together with their lifetime. 相似文献
44.
Yousuke Kurosaki Hisashi Mogi Hiroyasu Fujii Takeshi Kubota Morio Shiozaki 《Journal of magnetism and magnetic materials》2008
In order to reduce energy loss in motors, the use of high-efficiency non-oriented electrical steel sheets and an optimal motor core design are important. It is also crucial to minimize the deterioration of magnetic properties during the motor core manufacturing process. Accordingly, this report evaluates the effects of cutting and clamping methods on the deterioration factors of motor cores. Magnetic properties are largely influenced by both cutting and clamping methods. While it is difficult to avoid cutting and clamping altogether, it is necessary to adopt suitable production conditions and minimize the deterioration involved. 相似文献
45.
Keisuke Aizawa Satoru Yoshino Toshio Mogi Hiroumi Shiina Yuji Ogata Yuji Wada A. Koichi Hayashi 《Shock Waves》2008,18(4):299-305
While extensive studies have been conducted concerning the formation of detonation waves in various combustible gaseous mixtures
under static conditions since the 1950s, there is very little experimental work on simple flowing systems. In this study,
experiments on the deflagration to detonation transition (DDT) of a hydrogen–air flow system were carried out to see the effects
of tube diameter, equivalence ratio, and flow types in a premixed and non-premixed flow. Tube diameters used were 25, 50,
and 100 mm. The premixed experiments show that the larger tube diameter provides a wider range in run-up distance, reduction
of L
DDT/D (ratio of the run-up distance, L
DDT to tube diameter), and expansion of the detonable concentration limit by spreading the cell width. The result of the non-premixed
experiments show that similar values of the run-up distance to the premixed experiments are obtained at an equivalence ratio
of about 1.0, however, fluctuations of DDT occur near the DDT concentration limit. Under laminar flow conditions at a Reynolds
number of less than 2,300, the difference between the two systems could not be observed. However, when the Reynolds number
increases towards turbulent conditions, the DDT run-up distance decreases compared to that of static flow conditions.
This paper is based on work that was presented at the 21st International Colloquium on the Dynamics of Explosions and Reactive
Systems, Poitiers, France, July 23–27, 2007. 相似文献
46.
Yoshihisa Kurasawa Muneto Muramatsu Kaoru Yamazaki Setsuko Tajima Yoshihisa Okamoto Atsushi Takada 《Journal of heterocyclic chemistry》1986,23(3):959-960
The reaction of 3-(2,3-dihydro-4-methyl-3-thioxo-4H-1,2,4-triazol-5-ylmethylene)-2-oxo-1,2,3,4-tetrahydroquinoxaline 4 with o-chlorobenzenediazonium chloride gave 3-[α-(o-chlorophenylhydrazono)-2,3-dihydro-4-methyl-3-thioxo-4H-1,2,4-triazol-5-ylmethyl]-2-oxo-1,2-dihydroquinoxaline 6 , whose refluxing in phosphoryl chloride/pyridine afforded 1-(o-chlorophenyl)-3-(2,3-dihydro-4-methyl-3-thioxo-4H-1,2,4-triazol-5-yl)-1H-pyrazolo[3,4-b]quinoxaline 7. The reactions of 6 and 7 with nitrous acid resulted in sulfur extrusion to provide 1-(o-chlorophenyl)-3-(4-methyl-4H-1,2,4-triazol-5-yl)1H-pyrazolo[3,4-b]quinoxaline 8 and 3-[α-(o-chlorophenylhydrazono)-4-methyl-4H-1,2,4-triazol-5-ylraethyl]-2-oxo-1,2-dihydroquinoxaline 9 , respectively. 相似文献
47.
48.
Reforming of dimethyl ether with carbon dioxide into synthesis gas has been carried out over a mixed catalyst containing Cu-based methanol decomposition catalyst and alumina. The catalyst is found to show a high activity and selectivity. Catalyst stability and deactivation mechanism was also examined. 相似文献
49.
Dr. Takayoshi Oshima Dr. Tom Ichibha Kenji Oqmhula Dr. Keisuke Hibino Hiroto Mogi Dr. Shunsuke Yamashita Prof. Dr. Kotaro Fujii Dr. Yugo Miseki Prof. Dr. Kenta Hongo Dr. Daling Lu Prof. Dr. Ryo Maezono Dr. Kazuhiro Sayama Prof. Dr. Masatomo Yashima Dr. Koji Kimoto Prof. Dr. Hideki Kato Prof. Dr. Masato Kakihana Prof. Dr. Hiroshi Kageyama Prof. Dr. Kazuhiko Maeda 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(24):9823-9830
Undoped layered oxynitrides have not been considered as promising H2-evolution photocatalysts because of the low chemical stability of oxynitrides in aqueous solution. Here, we demonstrate the synthesis of a new layered perovskite oxynitride, K2LaTa2O6N, as an exceptional example of a water-tolerant photocatalyst for H2 evolution under visible light. The material underwent in-situ H+/K+ exchange in aqueous solution while keeping its visible-light-absorption capability. Protonated K2LaTa2O6N, modified with an Ir cocatalyst, exhibited excellent catalytic activity toward H2 evolution in the presence of I− as an electron donor and under visible light; the activity was six times higher than Pt/ZrO2/TaON, one of the best-performing oxynitride photocatalysts for H2 evolution. Overall water splitting was also achieved using the Ir-loaded, protonated K2LaTa2O6N in combination with Cs-modified Pt/WO3 as an O2 evolution photocatalyst in the presence of an I3−/I− shuttle redox couple. 相似文献