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1.
Large-scale travelling ionospheric disturbances (1.s. TIDs) have been investigated in order to derive the horizontal velocity dispersion by using f0F2 data from four ionospheric observatories in Japan. It was found that the horizontal phase trace velocity lies between 300 and 1000ms−1 with periods in the range 50 to 150 min. There is evidence that the derived velocity generally increases with increase of wave period. This is consistent with the dispersion predicted by the theory of the internal gravity waves. The azimuthal angles are distributed in ±35° sectors centered around 197° (measured clockwise from north), indicating that 1.s. TIDs may be obtainable when they are excited along the auroral zone of the same sector in longitude as that of the observatories. The average propagation direction shifts by 17° from south towards west. This clockwise shift is consistent with the rotation caused by the Coriolis effect. This means that the Coriolis effect cannot be ignored for the wave propagation of 1.s. TIDs. In addition to the positive correlation between TID speed and geomagnetic activity, the direction of wave propagation is found to be correlated with polar magnetic activity. The propagation direction is mostly southward during the period of large polar magnetic disturbances, while during the period of low magnetic activity the direction scatters considerably.  相似文献   

2.
We have observed Traveling Ionospheric Disturbances (TIDs) in the night-time D- and E-regions using a 2.66 MHz imaging Doppler interferometer radar. TIDs were observed in two distinct ways. In the first, the TID was manifested as discrete traveling surges, with average spacings of 54 min. The D-region surges were so well defined that they could be tracked as they passed close to overhead by using the phase differences across the antenna arrays. A velocity of 135 m s−1 to the south was measured, giving a horizontal wavelength of 440 km typical of medium scale TIDs. The direction of phase travel relative to the horizontal was −6° (i.e. downwards). These observations were made during a night of extraordinary OH infrared mesopause structure activity made visible by the presence of a total lunar eclipse. In the second type of TID observation, we show the Doppler interferometer analysis of ripples on the under surface of sporadic-E layers taken on two nights of significant OH infrared and OI 5577 Å wave activity. The TIDs were observed to propagate at speeds of 120–300 m s−1, with directions predominately toward the southwest, again typical of medium scale TIDs. These results show definite wave effects on MF radar returns and thus suggest that the measurement of mesospheric bulk winds with MF radars should be approached with some caution. Comparison of the TID characteristics with the OH structure characteristics show that the TIDs travel faster than the OH structures, have longer apparent horizontal wavelengths and generally travel in the opposite direction.  相似文献   

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4.
Experimental data on round-the-world HF radio signals near the terminator are given. The critical frequency of the ionospheric waveguide is found to be Fc ∼ 16–17 MHz. At frequencies F < Fc the group delay has a negative dispersion τdotg = ∂τ/∂F ⋍ −100 μs/MHz and τdotg ⋍ 80 μs/MHz for frequencies f > fc. Ray-tracing calculations are carried out. It is found that the low frequency branch of round-the-world signals (F < Fc) is formed mainly by waveguide modes and the high frequency branch (F > Fc) by 0 ricochet and hop modes.Experiments on waveguide modes escaping from the ionospheric channel due to field-aligned scattering by artificial ionospheric turbulence are carried out. The conditions for trapping of radio waves in the ionospheric waveguide are investigated. It is shown that if the gradient of the critical frequency F0F2 is less than minus 2 × 10−2 MHz/100 km radio wave trapping takes place in the ionospheric waveguide at frequencies exceeding by 1–2 MHz the maximum observed frequency of the hop mode. The frequency time characteristics of the mode and the geophysical conditions for the effective control of radio waves escaping from the waveguide are defined.  相似文献   

5.
This paper contributes to research on geographies of queer rural youth through an analysis of an award-winning young adult novel, The Miseducation of Cameron Post by Danforth (2012a. The Miseducation of Cameron Post. New York: Harper Collins). Three themes from the text are explored in this paper. The first is the well documented heterosexism of rural life. We note that the main protagonist, Cameron Post, experiences rural life on the margins, not only because of her queer identity but also because of her age and gender. A second theme in Danforth’s text is that rural spaces can be transgressively queer. In this respect the author subverts conflations of rurality and heterosexuality and urbanity and homosexuality as well as universalising notions of rurality as static, repressive and exclusive. The final theme emerging from a geographical reading of the text is that of placelessness. While highlighting the pervasiveness of this theme, we note that it elicits criticism from readers in relation to the book’s ending as it departs from the norms of familiar coming-out-narratives. In conclusion, we emphasise the efficacy of young adult literature as a source for furthering geographic knowledge about young people and sexuality.  相似文献   

6.
We analyze the general equilibrium effects of an asymmetric decrease in transport costs, combining a large-scale spatial dynamic general equilibrium model for 267 European NUTS-2 regions with a detailed transport model at the level of individual road segments. As a case study, we consider the impact of the road infrastructure investments in Central and Eastern Europe of the European Cohesion Policy. Our analysis suggests that the decrease in transportation costs benefits the targeted regions via substantial increases in gross domestic product (GDP) and welfare compared to the baseline, and a small increase in population. The geographic information embedded in the transport model leads to relatively large predicted benefits in peripheral countries such as Greece and Finland, which hardly receive funds, but whose trade links cross Central and Eastern Europe, generating profit from the investments there. The richer, Western European nontargeted regions also enjoy a higher GDP after the investment in the East, but these effects are smaller. Thus, the policy reduces interregional disparities. There are rippled patterns in the predicted policy spillovers. In nontargeted countries, regions trading more intensely with regions where the investment is taking place on average benefit more compared to other regions within the same country, but also compared to neighboring regions across an international border. We uncover that regions importing goods from Central and Eastern Europe enjoy the largest spillovers. These regions become more competitive and expand exports, to the detriment of other regions in the same country.  相似文献   

7.
This paper is concerned with the statistical errors which are present when wind velocities in the atmosphere are determined by the radar method known as the spaced antenna technique. It is assumed that the (complex) data is processed by the method known as full correlation analysis (FCA). A theory is first developed to give the error in the determination of the position of the maximum of a cross-correlation function and the value of lag such that the auto-correlation falls to a value equal to that of the crosscorrelation at zero lag. These are the basic quantities needed for the application of FCA. These error estimates are tested with a variety of numerically simulated data and shown to be realistic. The results are applied to real data and, using the standard techniques for the propagation of errors, they lead to estimates of the errors in the derived wind velocities. In order to test these estimates, an experiment was carried out in which two independent wind determinations were made simultaneously. The differences were used to obtain experimental estimates of the errors. It was found that the theory overestimates the error in the wind velocities by about 50%. Possible reasons for this are discussed.  相似文献   

8.
The modification of the raw clay by the potter to produce a paste suitable for the intended purposes adds a layer of obfuscation to the problem of provenancing the original clay source by chemical fingerprinting. By preparing different pastes from the same commercially available raw clay and their chemical analysis by Instrumental Neutron Activation Analysis, an experiment under controlled conditions (tempers, mixing ratios, firing temperatures and sampling methods) sheds light on the influence of different tempers.  相似文献   

9.
漂白对中国书画纸,特别是宣纸的影响情况未见系统的研究。为此,首先研究常用漂白剂-漂白粉(次氯酸钙)对宣纸的影响,又将硼氢化钠、过氧化氢、高锰酸钾和次氯酸钙四种漂白剂进行比较。结果表明,次氯酸钙具有加速纸张老化的作用,在文物保护过程中应该尽量避免使用漂白粉。不同的漂白剂对纸张的影响不同。因此在文物保护中,要弄清各种斑点产生的原因,首先采用水洗等物理方法,无法去除时再慎重选择漂白方法。  相似文献   

10.
Observations of winds in the 60–100 km height range were made at Mawson (68°S, 63°E) during December 1981 and January 1982 with the MF spaced antenna technique. The prevailing winds are in accord with other recent observations made at high latitudes and show a peak in the zonal wind near 80 km with westward winds of 30 m s −1. The meridional winds maximize near 90 km with an equatorward flow of 10 m s−1. The diurnal tidal components are in reasonable agreement with recent model predictions, especially in phase. The amplitudes tend to be larger than the model values. The semidiurnal tide is not as stable as the diurnal tide and shows evidence for interference effects between different modes.  相似文献   

11.
<万国公报>自改版后,利用其舆论影响,宣传西方资产阶级政治、经济、文化,建议中国进行改革,为维新变法运动提供了理论素材.在变法过程中,它直接推动了运动的开展,并对开启康有为、梁启超等变法人士的思想起了巨大的启蒙作用.  相似文献   

12.
The Bribie Island HF radar array (27°S, 153° E) can be set up to make angle of arrival and Doppler shift measurements throughout the range of spread-Es, layers. Results of this experiment show that the range spread seen on ionograms is not due to multiple reflection with varying obliquity, but rather a genuine height spread exists. Where velocity measurements can be reliably made, reflector velocity appears to be a slowly varying function of height. Spread-Es, can be blanketing or non-blanketing, sequential or non-sequential and at first impression it seems that the chief difference between spread-Es, and normal Es, is a small scale, partially transparent structure in lower regions that allows higher regions to be observed. It is suggested that on occasion spread-Es, irregularities are further modulated by the passage of gravity waves.  相似文献   

13.
14.
赵爽 《神州》2013,(35):30-30
特定社会环境中的宗教不仅影响其道德观、哲学思考,也对社会行为和语言文化产生着深远的影响。东西方主流宗教对语言、社会行为、文学、艺术等渗透影响,基督教文化与英语社会发展之间有内在联系。宗教在跨文化领域方面起着重要作用,了解宗教与文化之间的联系有助于更好地促进跨文化交际。  相似文献   

15.
赵爽 《神州》2013,(33):45-45
文化是人类社会的遗产,与宗教互相渗透影响。研究佛教对中国文化的影响有助于促进东西方交流。佛教与汉语、社会行为、艺术与文学有着根深蒂固的渊源。了解宗教与文化之间的联系有助于更好地促进跨文化交际。  相似文献   

16.
Ionospheric absorption measurements (Al method) made in the course of eight voyages by Soviet and other research vessels indicate that the global distribution of absorption shows a distinctive regional structure. Areas of abnormally high absorption in the neighbourhood of the equator have been located in the Pacific near the west coast of South America and in the Indian Ocean. The west Mediterranean area also shows abnormally high absorption. In some cases these areas of high absorption appear to coincide with areas of low nocturnal F-region electron density.  相似文献   

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18.
Given the recent focus of medical geography on the social influences of health and illness, this paper draws upon a socio‐theoretical framework to show the link between pregnancy health and the spaces of everyday life. The health of pregnant women is becoming increasingly important given that 85 percent of women work during their pregnancy. Employment during pregnancy is consistently linked with good health for infants; however, large discrepancies exist on the effects for employed mothers. This study estimates the health effect of women's employment during pregnancy with data from the National Longitudinal Survey of Children and Youth. Findings show that women's involvement in paid employment has a beneficial impact for infants compared to women not involved in paid labour. Women who work one job or more per week experience more health problems than women who work less than one job per week. Finally, women who work in male‐dominated and gender‐neutral workspaces experience significantly more prenatal problems than women in female‐dominated workspaces. In conclusion, there is evidence to support that differences in employment status, number of workplaces involved in and gendered workspaces influence the experience of health and illness that are negotiated in the spaces of everyday life.  相似文献   

19.
20.
Observations of neutral winds and temperatures obtained using a FabryPerot interferometer at Beveridge (37°28′S, 145°6′E) have been combined with h'F measurements from ionosondes at Canberra (35°21′S, 149°10′E) and Hobart (42°54′S, 147° 12′E). Data from 16 nights have been used to study the response (height change) of the F2-layer to changes in neutral wind and temperature. The observations have been compared with the ‘servo’ model of Rishbeth. It is found that the ‘night stationary level’ of the F2-layer depends on temperature, with the height changing by (13 ± 6) km per 100K. This agrees well with the prediction of the ‘servo’ model. There is reasonable overall agreement between the observations and the model predictions for the change in height produced by a given meridional wind. However, there is considerable scatter in the individual comparisons due to the approximations used to apply the theory to the observations. In particular, the effect of electric fields on the F2-layer height has been ignored.  相似文献   

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