共查询到19条相似文献，搜索用时 187 毫秒
1.
对富碳贫金属星CS 22964-161元素丰度的研究发现,该星碳和重元素丰度都高,这对于s-过程核合成研究是很有意义的.利用参数化模型研究了CS 22964-161的重元素丰度,重叠因子取值较高,r=0.57,这意味着原AGB星的初始质量应小于3M⊙.中子辐照量的取值为0.49mb-1,平均中子辐照量τ0≈0.87(T9/0.348)1/2,大于太阳系的平均中子辐照量,这是对s-过程元素,尤其是Pb元素超丰的有利解释.S-过程和r-过程分量系数都较小,这就意味着双星系统的轨道距离较远. 相似文献
2.
3.
采用对流参数化模型不但考虑了s-过程而且考虑了r-过程的作用模拟了4颗新观测到的Ba星,结果与观测符合得很好. 相似文献
4.
利用太阳系的重核素丰度,结合贫金属星重元素丰度的观测值及星系化学演化的计算结果,计算了不同金属丰度恒星三种典型重元素丰度的s-过程、r-过程贡献的相对比例。 相似文献
5.
6.
将TP-AGB星辐射s-过程核合成模型与双星系统星风吸积模型的轨道根数变化方程相结合,采用逐次脉冲吸积质量与混合的方法,对大量低质量双星系统进行演化计算,统计外赋AGB星形成铅星的分布规律.计算结果表明,双星系统的轨道周期、内禀AGB星的初始金属丰度及初始质量是影响外赋AGB演化为铅星的三个重要因素. 相似文献
7.
8.
根据最新的TP-AGB恒星模型,提出了一种计算AGB星外包层元素丰度的参数化方法,利用该方法计算了两颗纯s-过程AGB星的表面元素丰度,并通过与Aock等人计算结果的比较,对该方法进行了论证。 相似文献
9.
在观测到的极贫金属星Ba元素随金属丰度分布区域的左边界与单颗Ⅱ型超新星污染区域的r-过程元素丰度对应的假定下,采用Tsujimoto给出的Ⅱ型超新星爆发Mg元素的产量,利用Tsujimoto提出的方法,根据观测到的极贫金属星Ba和Mg丰度的左边界数值计算各种质量超新星r-过程的产量,得出星系中r-过程核合成的主要质量区间.根据所得到的不同质量Ⅱ型超新星r-过程的产量关系,改进Fields等人所提出的方法,解释观测到的贫金属星中子俘获元素的弥散性(scatter);根据三成份(晕、厚盘和薄盘)多相模型(气体、分子云、大小质量恒星以及剩余物质),利用所得到的Ⅱ型超新星的r-过程的产量计算了r-过程元素的均匀化学演化. 相似文献
10.
r-过程即快中子俘获过程,发生r-过程的天体物理环境有多个,理论分析和观测事实表明,r-过程主要发生在Ⅱ型超新星爆发的天体物理环境,宇宙中大多数的r-过程元素产生于这个过程. 相似文献
11.
湍流应力对AGB星结构与演化的影响 总被引：3，自引：0，他引：3
在混合程对流理论的基础上建立起考虑湍流应力作用的恒星结构与演化模型,并计算了8M⊙.研究表明,湍流应力对AGB星的演化有重要的影响,它使AGB星氦壳层热核反应更加不稳定,热脉动的发生大大提前而且更加频繁.这种热脉动的提前发生不仅使氦壳层内的光度、产能率、温度发生变化,同时使氢壳层内的各物理量和恒星表面的光度都同步发生改变.另外,湍流应力还使对流的混合作用加强,从而导致恒星内部及表面的各元素丰度都发生改变. 相似文献
13.
文章选取2001～2010年全国31个省域的数据,基于panel—data模型,采用空间面板回归和聚类分析方法,研究中国省域星级饭店规模与旅游经济增长的关系。按照旅游经济增长对星级饭店规模的弹性系数,将全国分为四类地区。研究发现：各类区域星级饭店对旅游经济的影响程度有很大差异,且存在一定的空间相关性。对于部分星级饭店规模已趋于饱和的省域,应注重星级酒店的市场营销,发展经济型酒店和家庭旅馆;而对于弹性系数较大的区域,则应加强发展星级酒店,扩大星级酒店的规模,提高接待水平。 相似文献
14.
“Comparator” accounts of associative conditioning (e.g., Gibbon & Balsam, 1981; Miller & Matzel, 1988) suggest that performance to a Pavlovian CS is determined, by a comparison of the US expectancy of the CS with the US expectancy of general background cues. Recent research indicates that variation in the excitatory value of cues in the local temporal context of a CS may have a profound impact on conditioned responding to the CS (e.g., Kaplan & Hearst, 1982), implicating US expectancy based on local, rather than overall, background cues as the critical comparator term for a CS. In two experiments, an excitatory training context attenuated responding to a target CS. In Experiment 1, the context was made excitatory by interspersing unsignaled USs with target CS-US trials. In this case, posttraining extinction of the conditioning context restored responding to the target CS. In Experiment 2, the target CS’s local context was made excitatory by the placement of excitatory “cover” stimuli in the immediate temporal proximity of each target CS-US trial. In this experiment, posttraining extinction of the proximal cover stimuli, not extinction of the conditioning context alone, restored responding to the target CS. An observation from both experiments was that signaling the otherwise unsignaled USs did not appear to influence the associative value of the conditioning context. The results are discussed in relation to a local context version of the comparator hypothesis and serve to emphasize the importance of local context cues in the modulation of acquired behavior. Taken together with other recent reports (e.g., Cooper, Aronson, Balsam, & Gibbon, 1990; Schachtman & Reilly, 1987), the present observations encourage contemporary comparator theories to reevaluate which aspects of the conditioning situation comprise the CS’s comparator term. 相似文献
15.
关于对数正态分布数学特征的两个结果 总被引：4，自引：0，他引：4
在算出对数正态分布的离差系数CV、偏度系数CS以及峰度系数CE的基础上,建立了这三个系数之间关系式:(1)CS=CV(CV2-1);(2)CE=(CV2 1)(CV4 4 CV2 6)-3.并作了详细证明. 相似文献
16.
在pH2.5～5.0条件下,Cu~(2+)与红色的氯磺酚S(CS)作用生成蓝色配合物,其最大吸收波长为650nm,比CS本身红移86nm。铜含量在0～20μg/10mL范围内符合Beer定律,表观摩尔吸光系数为6.87×10~4L·mol~(-1)·cm~(-1)。研究了CS与Cu~(2+)的光谱变化、反应条件、表面活性剂及共存物质的影响。十二烷基苯磺酸钠有增敏作用。方法操作简便,快速,灵敏度高,用于多种粮食,油料作物中铜(Ⅱ)含量的测定,结果满意。 相似文献
17.
The serial presentation of two different CSs, with each stimulus having an 8-sec duration (S18/S28), consistently has resulted in most of the shuttlebox avoidance responses being recorded to the S2 component. Experiment 1 attempted to attenuate this serial CS, delayed-response effect by conditioning the separate components of a serial CS prior to ordering them sequentially. Ten component-training trials were administered, with subjects receiving CS-US pairing to S1 only, S2 only, or to both S1 and S2 presented on separate trials. Two CS durations (8 or 16 sec) during this phase also were compared. Subjects were then given 100 avoidance test trials using the standard serial procedure. The 10 best avoidance responders in each group were selected for analysis. Shorter avoidance latencies were obtained only for subjects receiving component conditioning to S1. CS duration was not a factor in establishing the shorter latencies. Component conditioning to S2 resulted in increasing the total avoidances. Experiment 2 increased the number of component-training trials and the generality of the findings by using a different strain of rats and by extending the testing phase of the study so that all subjects could be included in the analysis. Comparable results were obtained. The theoretical implications of these data were discussed. 相似文献
18.
Rajaram Nityananda 《Resonance》2017,22(7):645-657
Stars, other than the Sun, appear to our unaided eyes as points of light. Large telescopes show an image whose size is dictated by refractive index irregularities in the Earth’s atmosphere. The size of this blurring is much greater than that of the star, and hence it is difficult to measure the stellar size. Fizeau showed how one might overcome this limitation using the two-slit interference technique. It was Michelson who carried out this programme and made the first direct measurement of the giant star Betelguse in the constellation of Orion. His value for the angular diameter, 47 milliarcseconds or 2.6×10?7 radians, was completely confirmed by later work following his methods. The key concept introduced was ‘fringe visibility’, which turned out to be very fruitful in the later development of optics as well as astronomy. 相似文献
19.
The efficacy of conditioned inhibition in a novel conditioned stimulus/conditioned inhibitor (CS/CI) compound was tested in 6-, 10-, and 14-week-old kittens. The conditioned response was suppression of respiration elicited by a 5.1-sec CS paired with a brief, mild footshock. During original inhibitory training, a CI was presented 2 sec after the onset of the CS, and the stimuli coterminated 3 sec later without the shock. As previously reported, the CI trained in this paradigm is more potent in older kittens but passes a summation test in all age groups (Dess & Soltysik, 1989). In the transfer test, the order of the CS and CI was reversed, so that the CI preceded the CS with no stimulus overlap. Transfer of inhibition to this new compound was virtually absent in the 6-week-old kittens and nearly perfect in the 14-week-old kittens. The CI alone (before CS onset) elicited a strong fear response in the youngest kittens, moderate fear in the 10-week-old group, and very little fear in the oldest group. The transferability of inhibitory training to a different temporal configuration of the CS and CI is absent at 6 weeks of age and fully developed 8 weeks later. 相似文献