http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
- 中文 을 입력하시려면 zhongwen을 입력하시고 space를누르시면됩니다.
- 北京 을 입력하시려면 beijing을 입력하시고 space를 누르시면 됩니다.
RISS 인기검색어
- 검색키워드
- 저자 : rez-Herná (검색결과 3 건)
- 무료
- 기관 내 무료
- 유료
-
Active tailoring of nanoantenna plasmonic fields using few-cycle laser pulses
Choi, S.,Ciappina, M. F.,Pé,rez-Herná,ndez, J. A.,Landsman, A. S.,Kim, Y.-J.,Kim, S. C.,Kim, D. American Physical Society 2016 Physical Review A Vol.93 No.2
<P>Plasmonic nanoatennas are a versatile tool for coherently manipulating light on a nanoscale by confining electric fields of the driving laser into subwavelength volumes, thereby significantly enhancing electric near fields. It is normally assumed that the time-dependent spectral properties of these near fields are independent of the duration of the driving laser pulse. Here we show that when a few-cycle laser pulse shines on a bow-tie nanoantenna, its spectral properties are dramatically modified, as evidenced by a large shift of the center wavelength of the near field, relative to the driving laser. In addition, for certain geometries, a second color appears in the near field, creating conditions for generation of an isolated attosecond pulse at megahertz repetition rate. Our results open the door to frequency-tunable ultrafast sources at nanometer scale without tuning the frequency of the driving laser.</P>
-
Detonation onset in a thermally stratified constant volume reactor
Sow, Aliou,Lee, Bok Jik,Herná,ndez Pé,rez, Francisco E.,Im, Hong G. Elsevier 2019 Proceedings of the Combustion Institute Vol.37 No.3
<P><B>Abstract</B></P> <P>Understanding detonation development from a flame kernel initiated by a pre-ignition event is important for modern internal combustion (IC) engines operating at boosted conditions. To provide fundamental insights into the effects of bulk gas temperature stratification on the characteristics of detonation development, one-dimensional high fidelity simulations were conducted for a constant volume reactor filled with a thermally stratified reactive stoichiometric hydrogen/air mixture. A linear temperature variation in the upstream end-gas was introduced to represent the thermal stratification of the bulk mixture, and the evolution from the initial deflagration flame front to detonation development was examined. The results showed that the bulk-gas temperature gradient has a significant effect on the run-up time and intensity of the developing detonation. Detailed analyses further revealed that the mechanism of detonation development is qualitatively different for the positive and negative temperature gradient cases. In the former, the detonation development is initiated by the end-gas autoignition at the wall, while the latter exhibits detonation development following the process of the self-acceleration of the flame similar to the deflagration-to-detonation transition. This behavior is attributed to the longer residence time in the end-gas allowing the reinforcement by the interaction of incident and reflected pressure waves during the flame propagation, and results in the peak pressure even higher than the case with the same level of positive temperature gradient. Furthermore, yet another detonation development pattern was observed for the negative temperature gradient condition in the presence of a uniform temperature region just ahead of the flame. In this case, autoignition was found to start in the middle of the bulk end-gas, and subsequently leads to the transition to detonation. The results demonstrate the importance of the bulk gas conditions in predicting the detonation development, which corroborate the existing theoretical framework.</P>
-
The pulsating hot subdwarf Balloon 090100001: results of the 2005 multisite campaign
Baran, A.,Oreiro, R.,Pigulski, A.,Herná,ndez, F. Pé,rez,Ulla, A.,Reed, M. D.,Rodrí,guez-Ló,pez, C.,Moskalik, P.,Kim, S.-L.,Chen, W.-P.,Crowe, R.,Siwak, M.,Armendarez, L.,Binder Blackwell Publishing Ltd 2009 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.392 No.3
<P>ABSTRACT</P><P>We present the results of a multisite photometric campaign on the pulsating B-type hot subdwarf star Balloon 090100001 (Bal09). The star is one of the two known hybrid hot subdwarfs with both long- and short-period oscillations, theoretically attributed to <I>g</I> and <I>p</I> modes. The campaign involved eight telescopes with three obtaining <I>UBVR</I> data, four <I>B</I>-band data and one Strömgren <I>uvby</I> photometry. The campaign covered 48 nights, providing a temporal resolution of 0.36 μHz with a detection threshold of about 0.2 mmag in <I>B</I>-filter data.</P><P>Bal09 has the richest pulsation spectrum of any known pulsating subdwarf B star, and our analysis detected 114 frequencies including 97 independent and 17 combination ones. Most of the 24 <I>g</I>-mode frequencies are between 0.1 and 0.4 mHz. Of the remaining 73, presumably <I>p</I> modes, 72 group into four distinct regions near 2.8, 3.8, 4.7 and 5.5 mHz. The density of frequencies requires that some modes must have degrees ℓ larger than 2. The modes in the 2.8 mHz region have the largest amplitudes. The strongest mode (<I>f</I><SUB>1</SUB>) is most likely radial, while the remaining ones in this region form two nearly symmetric multiplets: a triplet and quintuplet, attributed to rotationally split ℓ= 1 and 2 modes, respectively. We find clear increases of splitting in both multiplets between the 2004 and 2005 observing campaigns, amounting to ∼15 per cent on average. The observed splittings imply that the rotational rate in Bal09 depends on stellar latitude and is the fastest on the equator. We also speculate on the possible reasons for the changes of splitting. The only plausible explanation we find is torsional oscillation. This hypothesis, however, needs to be verified in the future by detailed modelling. In this context, it is very important to monitor the splittings on a longer time-scale as their behaviour may help to explain this interesting phenomenon.</P><P>The amplitudes of almost all terms detected in both 2004 and 2005 were found to vary. This is evident even during one season; for example, amplitudes of modes <I>f</I><SUB>8</SUB> and <I>f</I><SUB>C</SUB> were found to change by a factor of 2–3 within about 50 d during 2005.</P><P>We use a small grid of models to constrain the main mode (<I>f</I><SUB>1</SUB>), which most likely represents the radial fundamental pulsation. The groups of <I>p</I>-mode frequencies appear to lie in the vicinity of the consecutive radial overtones, up to the third one. Despite the large number of <I>g</I>-mode frequencies observed, we failed to identify them, most likely because of the disruption of asymptotic behaviour by mode trapping. The observed frequencies were not, however, fully exploited in terms of seismic analysis which should be done in the future with a larger grid of reliable evolutionary models of hot subdwarfs.</P>
연관 검색어 추천
이 검색어로 많이 본 자료
활용도 높은 자료
