On the intrinsic shape of the gamma-ray spectrum for Fermi blazars

The curvature of the γ-ray spectrum in blazars may reflect the intrinsic distribution of emitting electrons, which will further give some information on the possible acceleration and cooling processes in the emitting region. The γ-ray spectra of Fermi blazars are normally fitted either by a single power-law(PL) or a log-normal(call Logarithmic Parabola, LP) form. The possible reason for this difference is not clear. We statistically explore this issue based on the different observational properties of 1419 Fermi blazars in the 3 LAC Clean Sample. We find that the γ-ray flux(100 Me V–100 Ge V) and variability index follow bimodal distributions for PL and LP blazars, where the γ-ray flux and variability index show a positive correlation. However, the distributions of γ-ray luminosity and redshift follow a unimodal distribution. Our results suggest that the bimodal distribution of γ-ray fluxes for LP and PL blazars may not be intrinsic and all blazars may have an intrinsically curved γ-ray spectrum, and the PL spectrum is just caused by the fitting effect due to less photons.     

List of Forthcoming Papers

Other Index

List of Forthcoming Papers     

The equilibrium configuration of rapid rotating compact stars and some gravitational effects

In this paper, the equilibrium configurations of rapid rotating compact stars and some gravitational effects are studied within the general relativity by use of the Harrison-Wheeler equation of state and by the self-consistent field method. Numerical calculations show that the equilibrium configuration of a rotating star is a spheroid. For large spin velocities, say, ω > 3.0 × 10² sec⁻¹ the eccentricity and mass increase very rapidly as the angular velocity increases, for the critical angular velocity of the rotating star, the eccentricity is about 0.7, the increase in mass is about 10–35%. The difference of the gravitational redshifts at the surface of the star caused by rotation, and the difference of the light bending when the beam moves in the direction of rotation or in the opposite direction are obvious.     

Long-term statistics of extreme tsunami height at Crescent City

Historically, Crescent City is one of the most vulnerable communities impacted by tsunamis along the west coast of the United States, largely attributed to its offshore geography. Trans-ocean tsunamis usually produce large wave runup at Crescent Harbor resulting in catastrophic damages, property loss and human death. How to determine the return values of tsunami height using relatively short-term observation data is of great significance to assess the tsunami hazards and improve engineering design along the coast of Crescent City. In the present study, the extreme tsunami heights observed along the coast of Crescent City from 1938 to 2015 are fitted using six different probabilistic distributions, namely, the Gumbel distribution, the Weibull distribution, the maximum entropy distribution, the lognormal distribution, the generalized extreme value distribution and the generalized Pareto distribution. The maximum likelihood method is applied to estimate the parameters of all above distributions. Both Kolmogorov-Smirnov test and root mean square error method are utilized for goodness-of-fit test and the better fitting distribution is selected. Assuming that the occurrence frequency of tsunami in each year follows the Poisson distribution, the Poisson compound extreme value distribution can be used to fit the annual maximum tsunami amplitude, and then the point and interval estimations of return tsunami heights are calculated for structural design. The results show that the Poisson compound extreme value distribution fits tsunami heights very well and is suitable to determine the return tsunami heights for coastal disaster prevention.     

2.4m望远镜网络安全初步设计

云南天文台将在2.4m望远镜建立远程观测系统。由于远程观测系统通过网络实现通信,必然会面临网络上的各种威胁。为了保证整个网络系统的安全,避免各种不安全因素造成的损失。在对现在望远镜网络分析基础上设计了安全的网络结构,并实现了具有入侵检测功能的防火墙,这些措施初步保障了2.4m望远镜网络系统的安全。     

中国西北地区降水的演变趋势和年际变化

将 PCA和 SSA相结合 ,分析了中国西北地区降水量的演变趋势和年际变化 ,结果表明 :西北地区的降水变化的主要趋势是 1 960年代初多雨 ,到 1 970年代初演变为少雨 ,1 980年代又多雨 ,1 990年代少雨。这种趋势在陇南和陕西中南部是最显著的 ,天山北麓区也是相对显著区。西北地区降水主要存在准 8.5a、准 3～ 4a和准 5.1 a的甚低频振荡。甚低频振荡在降水中的重要性依次为准 8.5a、准 3～ 4a和准 5.1 a。准 8.5a振荡的振幅要比准 3～ 4a和准5.1 a振荡的振幅变化大。振荡位相在空间的分布并不完全一致。     

Accurate real‐time hybrid earthquake simulations on large‐scale MDOF steel structure with nonlinear viscous dampers

This paper presents real‐time hybrid earthquake simulation (RTHS) on a large‐scale steel structure with nonlinear viscous dampers. The test structure includes a three‐story, single‐bay moment‐resisting frame (MRF), a three‐story, single‐bay frame with a nonlinear viscous damper and associated bracing in each story (called damped braced frame (DBF)), and gravity load system with associated seismic mass and gravity loads. To achieve the accurate RTHS results presented in this paper, several factors were considered comprehensively: (1) different arrangements of substructures for the RTHS; (2) dynamic characteristics of the test setup; (3) accurate integration of the equations of motion; (4) continuous movement of the servo‐controlled hydraulic actuators; (5) appropriate feedback signals to control the RTHS; and (6) adaptive compensation for potential control errors. Unlike most previous RTHS studies, where the actuator stroke was used as the feedback to control the RTHS, the present study uses the measured displacements of the experimental substructure as the feedback for the RTHS, to enable accurate displacements to be imposed on the experimental substructure. This improvement in approach was needed because of compliance and other dynamic characteristics of the test setup, which will be present in most large‐scale RTHS. RTHS with ground motions at the design basis earthquake and maximum considered earthquake levels were successfully performed, resulting in significant nonlinear response of the test structure, which makes accurate RTHS more challenging. Two phases of RTHS were conducted: in the first phase, the DBF is the experimental substructure, and in the second phase, the DBF together with the MRF is the experimental substructure. The results from the two phases of RTHS are presented and compared with numerical simulation results. An evaluation of the results shows that the RTHS approach used in this study provides a realistic and accurate simulation of the seismic response of a large‐scale structure with rate‐dependent energy dissipating devices. Copyright © 2015 John Wiley & Sons, Ltd.     

四川盆地水热型地热资源构造成因模式

地处青藏高原东缘的四川盆地是一个群山环绕的叠合型沉积盆地,蕴含着丰富的地热资源。四川盆地具有突变型和渐变型两类盆山结构,二者的构造样式存在明显差异,对盆地及周缘的水热型地热资源分布具有明显的控制作用。通过解析盆地及周缘地质构造,明确了盆地不同构造单元的构造样式;详细对比分析已有的地热勘查案例的异同性,提出了褶皱型、单斜型和褶皱—断裂复合型等3大类水热型地热资源的构造成因模式;认为四川盆地形成与演化过程中,构造运动与水热型地热资源的形成密切相关,主要表现在：1）频繁不均匀升降运动导致构造—沉积格局分异,控制着地热储盖层岩性、组合及区域展布;2）构造抬升形成的不整合面和古岩溶作用极大改善了地热储层的孔渗物性和流体输导能力,形成了优质的碳酸盐岩孔洞型热储;3）断裂可能是地下热水的补给通道和输导系统,亦或是阻隔屏障,取决于断裂类型和断层两盘岩性配置关系;4）地下热水易于沿具走滑分量断层和张性断层进行补给和输导。