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Numerical Study of AGN Jet Propagation with Two Dimensional Relativistic Hydrodynamic Code
MIZUTA AKIRA,YAMADA SHOICHI,TAKABE HIDEAKI The Korean Astronomical Society 2001 Journal of The Korean Astronomical Society Vol.34 No.4
We investigate the morphology of Active Galactic Nuclei(AGN) jets. AGN jets propagate over kpc $\~$ Mpc and their beam velocities are close to the speed of light. The reason why many jets propagate over so long a distance and sustain a very collimated structure is not well understood. It is argued that some dimensionless parameters, the density and the pressure ratio of the jet beam and the ambient gas, the Mach number of the beam, and relative speed of the beam compared to the speed of light, are very useful to understand the morphology of jets namely, bow shocks, cocoons, nodes etc. The role of each parameters has been studied by numerical simulations. But more research is necessary to understand it systematically. We have developed 2D relativistic hydrodynamic code to analyze relativistic jets. We pay attention to the propagation velocity which is derived from 1D momentum balance in the frame of the working surface. We show some of our models and discuss the dependence of the morphology of jets on the parameter.
Semantics and Pragmatics of Pure Indexical Reference
( Yoko Mizuta ) 서울대학교 인지과학연구소 2019 Journal of Cognitive Science Vol.20 No.1
Kaplan (1989) proposed a semantic theory of pure indexicals, arguing that “I,” “here,” and “now’’ refer respectively to the agent, the place, and the time of the context of utterance. He focused on real-time, face-to-face communication, assuming “proper utterances,” that is, those utterances in which the agent is located in the place and time of the context of utterance. Kaplan claimed that in proper utterances the proposition “I am here now” is logically true, that is, true in every context of utterance. In the past few decades, the semantics of pure indexicals has been discussed beyond the scope of the work of Kaplan. Recorded and written messages are now a central concern of the literature and the logical truth of “I am here now” needs to be reexamined. In these messages, pure indexical references are to be communicated through the discrepancy between the spatial and temporal locations that the speaker and the hearer are in. In the literature, factors such as the speaker’s intention and social conventions have been mentioned as playing a key role in the identification of pure indexical references. However, the relation between these factors has been left unclear. Also, it remains to be clarified whether or not Kaplan’s semantic theory needs to be modified in order to accommodate the cases of recorded and written messages. This paper investigates the identification of pure indexical references from both semantic and pragmatic perspectives. It presents a theory which involves a minimum extension of Kaplan’s theory, introducing the notion of the “salient context of utterance.” Specifically, this paper argues the following: 1) it proposes a semantic theory which claims that “I,” “here,” and “now’’ refer respectively to the agent, the place, and the time of the pragmatically determined salient context of utterance, 2) it argues that “I am here now” is true in every salient context of utterance and provides a solution to the so-called “answering machine paradox,” 3) it identifies multiple pragmatic factors which contribute to the identification of the salient context of utterance, and 4) it proposes a hierarchy for the ways in which these multiple factors apply.
Hiroyuki Mizuta The Korean Society of Phycology 2002 ALGAE Vol.17 No.2
Seasonal changes of pigment compositionin two intertidal red algae, Gloiopeltis furcata (Postels et Ruprecht) J. Agardh, and Porphyra yezoensis Ueda, were investigated. Chlorophyll α and phycoerythrin levels were high during winter, but decreased in late spring or summer, with accompanying discoloration from deep red to green or yellow. This discoloation corresponded closely to the fluctuationof phycoerythrin content. Nevertheless, photosynthesis capacity was maintained by the increasing water temperature in the field, suggesting that large amounts of phycoerythrin are not necessary for photosynthesis. Phycoerythrin conten correlated significantly with nitrogen content in both species when the nitrogen level was greater than the level of critical content (1.30% DW in G. furcata, and 2.26% DW in P. yezoensis), indicating that phycoerythrin plays a more important role in the nitrogen status as a nitrogen pool than that of nitrogen critical content. Furthermore, the dependence level of the alage on phycoerythrin as a nitrogen pool was greater in P. yezoensis than in G. furcata because of the remarkable increase of phycoerythrin content in P. yezoensis with increasing jnitrogen content.
Foreign Bodies: The Problem of the Other in The Plumed Serpent
( Hiroko Mizuta ) 한국로렌스학회 2015 D.H. 로렌스 연구 Vol.23 No.2
This paper aims at reinterpreting The Plumed Serpent, which has been criticized from a moralistic point of view because of its elements of an apparently fascist aesthetics, by putting it in a new ethical context, where the problem of the response to otherness is foregrounded. For this purpose, Alphonso Lingis`s concept of “foreign bodies”-the bodies of those who have nothing in common-is employed. This concept provides a way to see Lawrence`s communal vision as a realistic one of a shared existence with the other, not as unrealistic fantasizing. In other words, the social and ethical aspects of Lawrence`s religious conviction are examined through a consideration of “the other`s body.” Furthermore, through the descriptions of the protagonist`s ambivalent attitude towards the new collective vision presented by Ramon and Cipriano, we can see that Lawrence addresses the problem of the “imperative of others,” who force us to respond. Mexico, its people, the religious leaders, Ramon and Cipriano, all of them are “foreign bodies” for the Westerner Kate. They show her a new mode of thought which is unthinkable for her and force her to respond to their assertion of otherness. At times, this repulses and confuses her. Her ambivalent attitude toward them demonstrates the difficulty of the reconciliation of the two extreme opposites, but at the same time it also suggests the possibility for accepting otherness as a questioning of the foundation of the Western way of thinking. Recognizing otherness as that which demands us to respond is the starting point of the real fusion or new collectivity that Lawrence sought. In this sense, this novel implies a ceaseless struggle for the union with otherness through the descriptions of the protagonist`s ambivalent responses.
Nanosilicon for single-electron devices
H. Mizuta,Y. Furuta,T. Kamiya,Y. T. Tan,Z.A.K. Durrani,S. Amakawa,K. Nakazato,H. Ahmed 한국물리학회 2004 Current Applied Physics Vol.4 No.2-4
This paper presents a brief overview of the physics of nanosilicon materials for single-electron device applications. We study howa nanosilicon grain and a discrete grain boundary work as a charging island and a tunnel barrier by using a point-contact transistor,which features an extremely short and narrow channel. Single-electron charging phenomena are investigated by comparing as-prepared devices and various oxidized devices. The optimization of grain and grain-boundary structural parameters is discussed forimproving the Coulomb blockade characteristics and realizing room temperature device operation.