Relativistic beaming in the central components of double radio quasars

Using a large sample of 78 well-observed double quasars, we have investigated several consequences of the relativistic beaming model. In this model the ratio of the strengths of the central component and outer lobes of a double source depends on whether the jet axis lies close to or away from the line of sight, If this is the actual situation, the fraction of emission from the core,f _c, may be used as a statistical measure of the orientation of the source and should be correlated with other source parameters which also depend on the inclination of the jet axis to the line of sight. We findf _c to be anticorrelated with the overall projected linear size of the extended emission but to exhibit a positive correlation with both the observed degree of misalignment from a collinear double structure, and the ratio of separations of the outer hotspots from the central component. As might be expected from these relationships, we also find sources of smaller projected linear sizes to appear more misaligned and the degree of misalignment to be correlated with the ratio of separations of the outer hotspots. All these correlations are consistent with the predictions of the relativistic beaming model.     

X线选射电噪活动星系核的多波段性质

基于被ROSAT全天区巡天观测和射电4．85GHz巡天观测同时探测到的活动星系核的大样本,研究了X射线选的射电噪活动星系核的多波段性质．通过分析该样本中的活动星系核的宽波段能量分布,确认了来自射电、光学和X射线波段的辐射光度之间的显著相关性．这种相关性对于类星体、赛弗特、蝎虎座天体和射电星系是有区别的．同时,探讨了从光学到X射线波段之间的谱指数与红移以及5000A和4．85GHz处的单色光度的相关性．     

酉阳河流域典型年汛期的基流分割研究

基流分割是水文学研究中的重难点问题之一,目前基流分割也存在许多方法.基于酉阳河典型年汛期实测日平均流量资料,分别采用Chapman-Maxwell改进方程数字滤波法一次滤波(参数N=1)以及二次滤波(参数N=2)、BFI(f)法、HYSEP固定步长法、HYSEP滑动步长法、HYSEP局部最小值法进行基流分割并对其结果进...     

辽宁省春玉米全育期的气候适宜度及年景评估

为评价气候变化对玉米生长的影响,以辽宁省为例选取1969—2018年18个气象站点的逐日实测气象数据,利用模糊数学法建立春玉米气候适宜度评估模型,以地理信息技术为依托,探究春玉米气候适宜度的时空特征,并在此基础上进行玉米气候年景的综合评估。结果表明:①辽宁省春玉米全生育期内日照、温度、降水适宜度波动幅度较大;然而春玉米种植气候适宜度的空间差异性较弱。②春玉米各生育期气候适宜度由高到低为:出苗期>开花期>成熟期>播种期。全生育期温度适宜度最高,日照适宜度次之,降水适宜度最低。③春玉米播种期、出苗期、开花期和成熟期的气候适宜度最高值分别出现在辽阳、葫芦岛、营口和铁岭。④春玉米气候年景准确率达64%,表明该评估方法可以较为准确地反映气候年景。近50 a辽宁省春玉米偏好的年景有4个年份(1971、1979、1993、1998年),较差的有1969年(4.98%)及1973年(5.59%)。     

过去60年中3—5年时间尺度的强ENSO过程与平流层环流异常的滞后耦合及其机理

基于1950—2009年60a月平均Nino3指数和NCEP/NCAR第一套等压面再分析资料,关注3—5 a时间尺度的强ENSO过程与平流层环流年际异常的时空联系及其机理,通过对此期间出现在3次持续强ENSO阶段中的11次3—5 a时间尺度的强ENSO过程的诊断表明,平流层环流的年际尺度异常与3—5 a时间尺度的强ENSO循环过程密切耦合。极夜急流强度趋于在ENSO暖/冷峰值之后减弱/加强,最大异常值多滞后ENSO峰值约1/4周期（接近1 a）,出现在ENSO峰值之后的下一年冬季;且3—5 a时间尺度的ENSO峰值愈强,滞后约1/4周期出现的热带外平流层纬向风的年际异常也愈强;平均而言,这种年际时间尺度的耦合关系,也对实际的季节尺度平流层极涡振荡的强度和性质有显著的调制作用。进一步研究这种滞后耦合关系与年际时间尺度的行星波活动异常的联系发现,在暖ENSO峰值所在的当年冬季,对流层高层被强迫出年际时间尺度的太平洋-北美（PNA）型异常环流,而与冷ENSO峰值相对应的是相反的太平洋 北美异常型;这种太平洋-北美型与平流层热带外地区的行星波1波的发展相联系;在ENSO峰值之后的下一年冬季,太平洋 北美型环流减弱但对流层高层的主要异常分布在中高纬度,多对应着平流层行星波2波的显著增强,与平流层极区最强的高度异常相联系。行星波活动所引起的经向动量通量和经向热量通量的辐合、辐散异常对平流层滞后异常响应的贡献,存在显著的阶段性差异,在不同的阶段两者可以共同起作用,也可以分别起作用。     

青藏高原多,少雪年后期西北干旱区降水的对比分析

利用１９５７－１９９０年高原地区的雪深,地面气温,地温以及西北干旱区部分站强降水量资料等,进行了高原地区多,少雪年积雪特下,地震热状况以及西北干旱区的期降水量的对比分析和相关分析。     

2000年下半年全球地震活动

2000年下半年全球共发生Mw≥6．5地震27次，其中23次为浅源地震，深源地震4次。发生Mw≥7．0地震5次，最大震级达Mw8．0。11月16日和17日，在俾斯麦群岛和所罗门群岛交界地区，发生了3次Mw≥7．8地震。2000年，全球地震活动处于1976年以来的较高水平。     

基于旅游需求的广西入境旅游时空变化研究

以广西入境旅游为研究对象,从旅游需求的角度出发,通过地理集中指数、年际集中指数、亲景度和旅游流等指标对广西入境旅游的时窄变化进行分析,总结了广西入境旅游的时空变化特征.按照对旅游目的地国际游客从来源到流向的分析思路,首先对广西入境旅游的时空集中性和亲景度进行分析,提出根据亲景度和年际集中指数对主要客源市场进行有重点、分层次开发.其次通过入境游客在广西区内的流向分析,指出应在把握游客需求趋势的基础上,促进优势旅游资源的开发和空间布局的优化.     

A model of the galactic tidal interaction with the oort comet cloud

We consider a model of the in situ Oort cloud which is isotropic with a random distrihution of perihelia directions and angular momenta. The energy distribution adopted has a continuous range of values appropriate for long-period (>200 yr) comets. Only the tidal torque of the Galaxy is included as a perturbation of comet orbits and it is approximated to be that due to a quasi-steady state distribution of matter with disk-like symmetry. The time evolution of all orbital elements can be analytically obtained for this case. In particular, the change in the perihelion distance per orbit and its dependence on other orbital elements is readily found. We further make the assumption that a comet whose perihelion distance was beyond 15 AU during its last passage through the Solar System would have orbit parameters that are essentially unchanged by planetary perturbations. Conversely, if the prior passage was inside 15 AU we assume that planetary perturbations would have removed the comet from the in situ energy distribution accessible by the galactic tide. Comets which had their perihelia changed from beyond 15 AU to within 5 AU in a single orbit are taken to be observable. We are able to track the evolution of 10⁶ comets as they are made observable by the galactic tidal touque. Detailed results are obtained for the predicted distribution of new (0 < 1/ < 10^–4 AU^–1) comets. Further, correlations between orbital elements can be studied. We present predictions of observed distributions and compare them with the random in situ results as well as with the actual observed distributions of class I comets. The predictions are in reasonable agreement with actual observations and, in many cases, are significantly different from random when perihelia directions are separated into galactic northern and southern hemispheres. However the well-known asymmetry in the north-south populations of perihelia remains to be explained. Such an asymmetry is consistent with the dominance of tidal torques today if a major stochastic event produced it in the past since tidal torques are unable to cause the migration of perihelia across the latitude barriers ±26°.6 in the disk model.     

A TRANSITION IN THE ACCRETION PROPERTIES OF AGN

This contribution focuses on the evidence for a bimodality in the luminosity believed to be associated with the accretion process in AGN. In particular, it will be stressed that this behavior does seem to be present in an analogous way both in radio-loud and radio-quiet AGN, as inferred from samples selected in an independent way. The found bimodality can be naturally – although not uniquely – interpreted in the frame of the ADIOS solution for radiative inefficient accretion flows. The (so far) qualitative analogy with the behavior of XRB provides an interesting perspective to find a unique framework for the accretion and jet production in accreting black hole systems.