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김순욱,Jeong-Sook Kim 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.5
Study of the physical origin for cataclysmic, transient phenomena such as superluminal jet ejection associated with outbursts, or flares, in relativistic compact objects have been a central issue in high energy astrophysics. A recent, successful observation of jet phenomena in cataclysmic variables proves that all compact components in close binaries, from black holes and neutron stars, to white dwarfs, can produce such relativistic flows as those observed with very long baseline interferometry, VLBI. VLBI is a type of astronomical interferometry at radio wavelengths. With simultaneous observations with many radio telescopes separated by hundreds to thousands of kilometers from each other, the interferometric principle makes it possible to observe distant astrophysical objects of a few milli-arcseconds or less. The data analysis of VLBI observations, however, usually requires appreciable lengths of time; hence, immediate cataclysmic phenomena cannot be noticed. A realtime analysis is, however, necessary to decide whether to continue follow-up observations. The recent development of electronic VLBI (e-VLBI) techniques has overcome such hurdles through the realization of real-time correlation. The e-VLBI technique is, in particular, very powerful for studying the complex phenomena associated with sudden increases in photon fluxes in celestial objects such as supernovae, gamma-ray bursts, and compact objects. We discuss the necessity of e-VLBI by showing an example of the position correction for a calibrator to the target that we performed as a VLBI experiment. Study of the physical origin for cataclysmic, transient phenomena such as superluminal jet ejection associated with outbursts, or flares, in relativistic compact objects have been a central issue in high energy astrophysics. A recent, successful observation of jet phenomena in cataclysmic variables proves that all compact components in close binaries, from black holes and neutron stars, to white dwarfs, can produce such relativistic flows as those observed with very long baseline interferometry, VLBI. VLBI is a type of astronomical interferometry at radio wavelengths. With simultaneous observations with many radio telescopes separated by hundreds to thousands of kilometers from each other, the interferometric principle makes it possible to observe distant astrophysical objects of a few milli-arcseconds or less. The data analysis of VLBI observations, however, usually requires appreciable lengths of time; hence, immediate cataclysmic phenomena cannot be noticed. A realtime analysis is, however, necessary to decide whether to continue follow-up observations. The recent development of electronic VLBI (e-VLBI) techniques has overcome such hurdles through the realization of real-time correlation. The e-VLBI technique is, in particular, very powerful for studying the complex phenomena associated with sudden increases in photon fluxes in celestial objects such as supernovae, gamma-ray bursts, and compact objects. We discuss the necessity of e-VLBI by showing an example of the position correction for a calibrator to the target that we performed as a VLBI experiment.
김순욱 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.60 No.9
The observed features of typical, symmetric outbursts in the neutron star X-ray transient Aquila X-1 such as the rise, the plateau in the maximum, and the decay, are reproduced with a timedependent disk instability model. No external effect such as irradiation is necessary to account for the observation. In the model, a truncated inner disk radius that is more than ten times larger than the magnetically truncated one and that is plausibly appropriate to the scale proposed by hot flow models must be adopted. The model shows that such symmetric outbursts in Aql X-1 may be inside-out outbursts, while outside-in outbursts have been conjectured based on observations. The implication of the presented model, with observations, is discussed together.
금속사출성형을 위한 W-10wt.%Cu 분말의 제조에 관한 연구
김순욱,손찬현,김영도,문인형 한국분말야금학회 2001 한국분말재료학회지 (KPMI) Vol.8 No.4
Recent remarkable progress in the semiconductor industry has promoted smaller size of semiconductor chips and increased amounts of heat generation. So, the demand for a substrate material to meet both the characteristics of thermal expansion coefficient and heat radiation has been on the increase. Under such conditions, tungsten(W)-copper(Cu) has been proposed as materials to meet both of the above characteristics. In the present study, the W-10wt.%Cu powders were synthesised by the mixing and hydrogen reduction of the starting mixture materials such as W-Cu, $W-CuCl_2$and $WO_3-CuCl_2$ in order to obtain the full densification. The W-10wt.%Cu produced by hydrogen reduction showed the higher interparticle friction than the simple mixed W-10wt%Cu because of the W agglomerates. In the dilatometric analysis the W-10wt.%Cu prepared from the $W-CuCl_2$was largely shrank by heating up $1400^{\circ}C$ at the constant heating rate of $5^{\circ}C$/min. The possibility of application of metal injection molding (MIM) was also investigated for mass production of the complex shaped W-Cu parts in semiconductor devices. The relationship between the temperature of molding die and the pressure of injection molding was analyzed and the heating up stage of 120-$290^{\circ}C$ in the debinding process was controlled for the most suitable MIM condition.