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 : Stan (검색결과 43 건)
- 무료
- 기관 내 무료
- 유료
-
-
Modeling Gamma-Ray Emission From the High-Mass X-Ray Binary LS 5039
Stan Owocki,Atsuo Okazaki,Gustavo Romero 한국우주과학회 2012 Journal of Astronomy and Space Sciences Vol.29 No.1
A few high-mass X-ray binaries–consisting of an OB star plus compact companion–have been observed by Fermi and ground-based Cerenkov telescopes like High Energy Stereoscopic System (HESS) to be sources of very high energy (VHE; up to 30 TeV) γ-rays. This paper focuses on the prominent γ-ray source, LS 5039, which consists of a massive O6.5V star in a 3.9-day-period, mildly elliptical (e ≈ 0.24) orbit with its companion, assumed here to be an unmagnetized compact object (e.g., black hole). Using three dimensional smoothed particle hydrodynamics simulations of the Bondi-Hoyle accretion of the O-star wind onto the companion, we find that the orbital phase variation of the accretion follows very closely the simple Bondi-Hoyle-Lyttleton (BHL) rate for the local radius and wind speed. Moreover, a simple model, wherein intrinsic emission of γ-rays is assumed to track this accretion rate, reproduces quite well Fermi observations of the phase variation of γ-rays in the energy range 0.1-10 GeV. However for the VHE (0.1-30 TeV) radiation observed by the HESS Cerenkov telescope, it is important to account also for photon-photon interactions between the γ-rays and the stellar optical/UV radiation, which effectively attenuates much of the strong emission near periastron. When this is included, we find that this simple BHL accretion model also quite naturally fits the HESS light curve, thus making it a strong alternative to the pulsar-wind-shock models commonly invoked to explain such VHE γ-ray emission in massive-star binaries.
-
Political Connections and Firm Performance: The Case of Hong Kong
Stan Hok-Wui Wong 동아시아연구원 2010 Journal of East Asian Studies Vol.10 No.2
Business interests are overrepresented in Hong Kong’s nominally democratic political institutions. Many in Hong Kong perceive this as evidence of the existence of “collusion between government and business,” a phenomenon that has stirred public concerns in the city since its sovereignty transfer. Although anecdotal accounts abound, no systematic analysis has been conducted to evaluate the validity of this perception. In this article I use a rich firm-level dataset to offer the first systematic assessment of the effects of political connections on firm performance in Hong Kong. I define politically connected firms as firms that have stakeholders concurrently holding a seat on the Election Committee, a constitutional body that elects the city’s chief executive. I found evidence, though not overwhelming, consistent with the “collusion” hypothesis: political connections do improve firm performance measured by return on equity and market-to-book ratio. The improvement is unlikely due to unobserved confounding factors such as firms’ inherent ability. As for the origin of the political connections, the data show that a firm’s economic power has little predictive value of its connections to the Election Committee. Rather, number of employees matters; firms that hire fewer workers were more likely to gain a seat on the 1997 Election Committee. This result may suggest that Beijing plays a more dominant role in the formation of political connections—that serve Beijing’s co-optation needs rather than the interests of powerful firms that may have a desire to “capture” the state.
-
MULTI-SCALE MODELS AND SIMULATIONS OF NUCLEAR FUELS
Stan, Marius Korean Nuclear Society 2009 Nuclear Engineering and Technology Vol.41 No.2
Theory-based models and high performance simulations are briefly reviewed starting with atomistic methods, such as Electronic Structure calculations, Molecular Dynamics, and Monte Carlo, continuing with meso-scale methods, such as Dislocation Dynamics and Phase Field, and ending with continuum methods that include Finite Element and Finite Volume. Special attention is paid to relating thermo-mechanical and chemical properties of the fuel to reactor parameters. By inserting atomistic models of point defects into continuum thermo-chemical calculations, a model of oxygen diffusivity in $UO_{2+x}$ is developed and used to predict point defect concentrations, oxygen diffusivity, and fuel stoichiometry at various temperatures and oxygen pressures. The simulations of coupled heat transfer and species diffusion demonstrate that including the dependence of thermal conductivity and density on composition can lead to changes in the calculated centerline temperature and thermal expansion displacements that exceed 5%. A review of advanced nuclear fuel performance codes reveals that the many codes are too dedicated to specific fuel forms and make excessive use of empirical correlations in describing properties of materials. The paper ends with a review of international collaborations and a list of lessons learned that includes the importance of education in creating a large pool of experts to cover all necessary theoretical, experimental, and computational tasks.
-
MULTI-SCALE MODELS AND SIMULATIONS OF NUCLEAR FUELS
Stan, Marius Korean Nuclear Society 2009 Nuclear Engineering and Technology Vol.41 No.1
Theory-based models and high performance simulations are briefly reviewed starting with atomistic methods, such as Electronic Structure calculations, Molecular Dynamics, and Monte Carlo, continuing with meso-scale methods, such as Dislocation Dynamics and Phase Field, and ending with continuum methods that include Finite Element and Finite Volume. Special attention is paid to relating thermo-mechanical and chemical properties of the fuel to reactor parameters. By inserting atomistic models of point defects into continuum thermo-chemical calculations, a model of oxygen diffusivity in $UO_{2+x}$ is developed and used to predict point defect concentrations, oxygen diffusivity, and fuel stoichiometry at various temperatures and oxygen pressures. The simulations of coupled heat transfer and species diffusion demonstrate that including the dependence of thermal conductivity and density on composition can lead to changes in the calculated centerline temperature and thermal expansion displacements that exceed 5%. A review of advanced nuclear fuel performance codes reveals that the many codes are too dedicated to specific fuel forms and make excessive use of empirical correlations in describing properties of materials. The paper ends with a review of international collaborations and a list of lessons learned that includes the importance of education in creating a large pool of experts to cover all necessary theoretical, experimental, and computational tasks.
-
Immigrants as Voters in Electoral Autocracies: The Case of Mainland Chinese Immigrants in Hong Kong
Stan Hok-Wui Wong,Ngok Ma,Wai-man Lam 동아시아연구원 2018 Journal of East Asian Studies Vol.18 No.1
Migration to electoral autocracies has become increasingly common. Extant studies, however, accord little attention to the immigrants' influences on the domestic politics of these regimes. We argue that immigrants have attributes (status quo bias and lack of prior exposure to local politics) that make them an attractive co-optation target of the authoritarian regime. We provide a case study of mainland Chinese immigrants in Hong Kong to illustrate our argument. Since the sovereignty transfer, the Hong Kong government has devised various schemes to attract these immigrants, while pro-establishment political parties and groups have actively sought to co-opt them. Using two distinct public opinion surveys, we also find that immigrants are more likely to approve of the political and economic status quo, and less likely to vote for pro-democracy opposition parties than the natives. In addition, we find no evidence that exposure to political information can change the immigrants' vote choice.
-
-
-
-
Petition and Repression in China’s Authoritarian Regime: Evidence from a Natural Experiment
Stan Hok-Wui Wong,Minggang Peng 동아시아연구원 2015 Journal of East Asian Studies Vol.15 No.1
China has established a petition system to elicit information about grievances. However, the petition system may have perverse effects because it also reveals to the center the failure of local-level officials to resolve those grievances. Anecdotal accounts suggest that local officials have incentive to silence petitioners, often with the use of repression. In this article we study whether non–regime threatening petitions would provoke local governments’ coercive response. To tackle the endogenous relationship between petition and repression, we take advantage of a natural experiment afforded by a change in hydroelectricity policy in China. In particular, we use provincial hydropower outputs as an instrument to identify citizen petitions. We find that citizen petitions significantly increase a province’s spending on its repressive apparatus. The results suggest a paradoxical outcome of China’s petition system: while it may help reduce the national authority’s use of repression, it has caused an explosion of repression within the authoritarian system as a whole.
연관 검색어 추천
이 검색어로 많이 본 자료
활용도 높은 자료
