Nocturnal stratification of the ionospheric F-layer over Wuchang,China

Examples are given in the present paper of nocturnal ionospheric stratifications in lower midlatitudes, with the following characteristics:

• 1.(1) clear night-time stratification or low frequency F retardation, implying stratification
• 2.(2) a marked decrease in foF2 and a marked increase in h'F2 and hpF2
• 3.(3) a marked increase in electron concentration under the peak
• 4.(4) a close correlation with polar substorms, as deduced from the local magnetograms. It is suggested that the stratifications are due to particle precipitation and to modification of the low-latitude electric field by polar substorms.

     

A preliminary experimental test of ionospheric tomography

A preliminary experiment to test the application of computerized tomography (CT) to ionospheric imaging is described. Co-ordinated observations are presented in which radio transmissions from NNSS satellites were used to measure the total electron content required for the tomographic image of electron density. Simultaneous measurements of electron density by the EISCAT ionospheric radar facility were made for comparison. The results show that a large-scale ionospheric electron density gradient reconstructed by the tomographic technique is also seen in the EISCAT observations.     

试析历史古建筑复原陈列的基本定位

在历史古建筑保护工作中,复原陈列是用来表现古建筑文化底蕴和人文内涵的重要手段。其通常借助于实物媒介,以陈列艺术的独特语言表现活态的过往历史,再现原生态的人文风貌。在具体的复原展示中,主要依据古建筑物的历史价值、科学价值、艺术价值的差异情况,而决定"物"与"景"组合展示的最终导向。     

浅析古书画题款之转变

写在书籍、字面、碑帖等前面的文字叫题,后面的叫跋。对于中国画来说,凡是画上的题字钤印均属题款。绘画在汉时却是一直无作者名款的,有的仅是榜题、画题和画赞,故仅能成为雏形,而不能称题款。中国画题款自宋元以后已逐步成为中国画章法不可缺少的组成部分,形成诗书画印四位一体的独特艺术形式。题款到了元风气为之一变,强调诗书画三者结合,此风气自此大盛,一直延续至近现代。书画作品题款中历朝历代均存在避讳,根据不同历史时期所避讳的字,亦可以判定书画作品的时代。     

黄河流域早期铜器演进初探

黄河流域是中国早期铜器起源与发展的关键区域,早期铜器的演进受社会复杂化程度制约。在文明化进程的视野下,本文通过用铜遗存的考古信息与社会经济背景,将黄河流域早期铜器的演进分为早期用铜的萌芽、发展初期及区域化特征形成三个阶段,初步阐释铜制品从出现到规模化使用的过程。人群流动、定居农业、手工业生产、城市与权力的集中是影响黄河流域早期铜器演进模式的重要因素。大体在公元前2300年至前1400年的文明进程中,黄河上游铜器的制作与使用具有相似的风格及开放共融的特征,而黄河中下游地区防御性城市与权力的发展,推动了铜器技术与社会功用的本土化转变。     

新征集唐《罗州玠墓志》志主的胡人身份浅析

本文通过对新征集的唐代《罗州玠墓志》的内容进行分析与考证,还原志主罗州玠真实的胡人身份,探索通过丝绸之路进入中原的胡人的汉化过程,以及其在当时的生活情况,并为今后这一方面的研究增添新的资料。     

A model of ionospheric image structure underneath a braking,cross-field plasma jet

A plasma jetting across the geomagnetic field above the ionosphere tends to brake by ohmic dissipation of Pedersen currents. The braking can affect the ionosphere underneath if the associated Pedersen drifts are intense and prolonged enough to cause cumulative image structuring. We examine such image structuring for the parameter regime of forthcoming CRRES releases, involving photo-ionization of kilograms of barium vapor moving at orbital velocity. The resultant structuring in the upper E-region offers possible diagnostic tell-tales of the braking process.     

TID,electron density and ionospheric sounding

For the approximation of a parabolic ionospheric layer, the relation between the fluctuation amplitude of radio phase path in HF vertical sounding and sinusoidal disturbance parameters has been found. Horizontal disturbance propagation has not been considered. The determining factors are the relation of the vertical wavelength of the disturbance to the half-thickness of the layer and between operating and critical frequency.     

简析西汉崖洞墓的防盗设施

汉代王陵防盗设施形式多样,较为全面。本文根据已公布的考古资料,结合历史文献对已发掘的西汉崖洞墓防盗设施略作探讨,以展见西汉诸侯王对墓葬修建的重视。     

新发现庞留唐墓壁画初探

庞留唐墓的发现特别是壁画出现,使我们对初唐以及盛唐墓中的大量的壁画得以比较分析,可以清楚地看到,在所发现的唐代壁画中,还是能全面地反映初唐、盛唐时期壁画艺术风格和审美特征及变化过程的。从初唐到盛唐,唐代绘画经过了北朝遗风、初唐风格、武周风格和盛唐风格的演变发展过程。该唐墓壁画的发现,为我们研究唐早期、中期的绘画提供了宝贵的资料依据。     

舞筵与胡腾·胡旋·柘枝舞关系之初探

舞筵作为外来之物出现在胡腾和胡旋舞表演场景中。考古资料显示的唐代舞筵与文献资料的相关记载大致对应,因描写对象与范围所限,舞筵与胡腾、胡旋舞、柘枝舞的关系并不明确,但其外来性与道具功能所带来的视觉冲击力和渲染作用十分明显。     

重庆钓鱼城遗址悬空卧佛彩绘颜料初步分析

钓鱼城悬空卧佛造像系创作于晚唐时期的一尊巨型石刻,具有极高的历史、艺术、科学、宗教价值,但造像保存现状较差,存在颜料脱落、酥碱粉化、起甲等病害,亟待保护修复。为了解悬空卧佛彩绘颜料层的成分与结构,采用金相显微镜、拉曼光谱、X射线荧光(XRF)、X射线衍射(XRD)、扫描电镜-能谱仪(SEM-EDS)等多种现代方法与技术对彩绘样品进行了分析。结果表明:所用红色颜料为铁红、铅丹;蓝色颜料为群青;绿色颜料为碱式氯化铜;青色颜料为墨绿砷铜矿;白色颜料为硫酸铅;局部有贴金。结果还表明,该造像历史上曾多次重绘。本研究成果以期填补钓鱼城悬空卧佛研究的空白,同时为修复工作的开展提供科学依据。     

山东莱芜嬴城遗址炼铜渣初步研究

为了解山东地区早期冶金技术的发展情况,采用扫描电子显微镜分析等方法,对莱芜赢城冶炼遗址出土的3件炉渣进行了检测。结果表明其中2件为红铜还原渣,1件为砷铜熔炼渣。由此推测该遗址铜的还原可能存在两种工序,并且掌握了利用含砷矿物"点炼"铜液得到砷铜的技术。遗址所利用的铜可能来自于北江水铜矿,砷可能来自于鲁中山区,炉渣所属的时代应与遗址出土的商周青铜器年代相近。     

A case study of a high latitude ionospheric electron density depletion

Incoherent scatter measurements inside and outside an ionospheric electron density depletion are described. The density depletion is probably caused by an enhancement of NO⁺-ions and subsequent dissociative recombination. The NO⁺-ions are increased because high electric fields present at the geographical location of the density depletion speed up the reaction O⁺ + N₂ → NO⁺ + N. The electron as well as the ion temperature within the density depletion are strongly enhanced, the latter due to Joule heating, also caused by the electric field.     

从青海出土文物浅析隋唐时期联珠纹饰的盛行及衰微

青海位于中原、西域、北方草原民族等文化圈的交融地带,出土了大量的隋唐时期联珠纹饰样的文物,生动地反映了隋唐时期中西经济、文化交流的盛况。萨珊联珠纹在青海地区的流行,对研究隋唐时期中、西亚文化在青海的传播发展,以及"丝绸之路青海道"在中西交通史上的历史地位具有重要意义     

A scintillation theory of fading in long distance HF ionospheric communications

Scintillation theory is used to study the fading of radio waves returned from the ionospheric F-region in the HF band at oblique incidence. For both low and high penetration frequencies calculations are made as a function of wave frequency, but emphasis is given to behaviour near the maximum usable frequency for one-hop F-transmission over distances up to 4000 km. Estimates are made of

• 1.(i) the fluctuations of phase both for long-term (~ 1h) and for short-term (~ the fading correlation time),
• 2.(ii) the fading correlation distance,
• 3.(iii) the quasi-period of fading,
• 4.(iv) the twinkling correlation distance,
• 5.(v) the quasi-period of twinkling,
• 6.(vi) the angular departure of the arrival azimuth from the mean and
• 7.(vii) the correlation bandwidth.

The slow fluctuations often experienced in long distance HF radio communications are a manifestation of twinkling, rather than fading. Under normal conditions in the F-region the correlation bandwidth is so large that the bandwidth of transmission at HF is controlled by the dispersive properties of the ionosphere, rather than by the scattering properties. The reverse is true in the presence of spread-F. For sufficiently strong spread-F the correlation bandwidth for long distance HF radio communications is of the order of only 10 Hz, thereby creating the phenomenon known as flutter fading. Theoretical estimates of the scintillation parameters are compared with experience in long distance HF ionospheric communications over the last 60 years. Agreement is promising, but future experiments should be designed in the light of theory; existing observational data do not provide some of the information needed.     

A study of ionospheric electron density deviations during two great storms

A large foF2 data base has been collected for the two great storms occurring in March and October 1989. Plots of foF2 deviations versus time and latitude show the large depressions cannot be caused by a composition change alone; the storm induced dynamo electric field must also play an important role, especially for low latitudes. The observed ionospheric response is hemispherically asymmetric, with the autumnal hemisphere suffering a longer lasting, more latitudinally extended, and deeper depression.