A method of determining horizontal structure of the ionosphere from backscatter ionograms

We have developed a technique lor oblique backscatter sounding (OBS) ionogram inversion as a diagnostic tool for the horizontally inhomogeneous structure of the ionosphere. Input data for the method include the leading edge of a backscalter ionogram that is measured through soundings in a given direction, and the vertical electron density profile measured over the sounding station or over some other site lying in the sounding direction. The method may be useful for reconstructing the two-dimensional electron density distribution in a vertical plane aligned with the direction of sounding. The inverse problem has been solved using the Newton Konlorovich method and the Tikhonov regularization method. The algorithm we have developed was tested against model data, that is, OBS ionograms synthesized using geometrical optics calculations for different models of the inhomogeneous ionosphere. Test results demonstrate that our method converges reliably, is stable to measurement errors and provides a good accuracy of reconstruction of inhomogeneous structures with scales of 100 2000 km. This indicates that this method shows promise as an operative remote diagnostic tool for ionospheric irregularities of natural and artificial origin.     

Electrojet irregularity parameters from daytime equatorial scintillations

The second moment of the complex amplitude or the mutual coherence function (MCF) for transionospheric VHF radio waves transmitted from the geostationary satellite ATS-6 is computed from daytime amplitude and phase scintillations recorded at an equatorial station, in order to study the structure of electrojet irregularities. The shape of the correlation function for fluctuations in the integrated electron content along the signal path is deduced by using a theoretical relationship between this correlation function and the MCF which is based on the assumption that the irregularities are “frozen”. Further, using a power-law spectrum to describe the electrojet irregularities, the outerscale l_o associated with the spectrum as well as the r.m.s. density fluctuation are estimated from theoretical fits to the computed values. The irregularity drift speeds V_o transverse to the signal path, for the scintillation events studied here, are derived from power spectra of weak scintillations. On the basis of a relationship between l_o and V_o suggested by a linear theory of the gradient-drift instability, the effective Hall conductivity is estimated to be about five times the effective Pedersen conductivity in the electrojet region.     

Synthesis of oblique ionograms from vertical ionograms using quasi-parabolic segment models of the ionosphere

This paper describes a method of synthesizing oblique ionograms from vertical ionograms based on representing the ionosphere by multiple quasi-parabolic segments (QPS). The advantage of this approach is that it allows analytical solutions to be obtained for several ray parameters when the Earth's magnetic field is neglected and the ionosphere is spherically stratified. The no-field results are representative of the ordinary mode. In addition, results for the extraordinary mode can be obtained by introducing a perturbation to the effective frequency and modifying the no-field results. The method is illustrated by comparing synthesized oblique ionograms with observed ionograms and with results obtained for the ordinary mode using the classical method.     

Spectral behaviour of TIDs detected from rapid sequence ionograms

The main purpose of this paper is to illustrate the usefulness of ionosonde observations in the study of the spectral evolution of travelling ionospheric disturbances (TIDs). An inversion method is introduced to yield the spatial and temporal variation of the ionospheric velocity from data of modern ionosondes or rapid-run ionosondes. Some inversion results of rapid sequence ionograms are spectrally analysed to obtain the height- and time-dependent power spectra of TIDs, and the evolution of these spectra is discussed in detail. It is found that spectral peaks shift regularly with time. As time increases, the peaks of the lower frequency components or those at the lower heights tend to shift towards lower frequency, while those of higher frequency or at higher altitudes lend to higher frequency. This property is explained by the current dispersion theory of atmospheric gravity waves. It is concluded that the spectral behaviour of TIDs can be well studied by using ground-based HF techniques, such as ionosonde observation.     

The effects of travelling ionospheric disturbances on ionograms

The numerical synthesis of ionograms by ray-tracing in an analytic two-dimensional ionosphere is simplified by a technique which avoids the usual wastage of ray tracings. The technique is particularly suitable for obtaining ionogram sequences corresponding to a moving ionospheric disturbance. It is applied firstly to a moving tilted ionisation increase, which gives the familiar travelling-cusp records. Ionograms do not give a good measure of the vertical distribution of ionisation, and in the case considered lead to an overestimate of the horizontal size of the increase by a factor of about 2. For a travelling ionisation decrease or trough, the ionograms show an additional U-shaped trace overlapping the main trace. Calculated ionograms agree closely with some observations. It is difficult to obtain any measure of the size of the electron-density decrease; critical frequency scalings may give no indication of the passage of an intense disturbance. Similar results are obtained for a wavelike perturbation in an exponential topside ionosphere. Topside ionograms then show multiple ‘nose’ traces, following in general the curve for the unperturbed ionosphere. It is suggested that the multiple echoes frequently observed on topside ionograms may, in some cases, be due to refraction in large disturbances rather than the commonly-assumed ducting mechanism.     

The global distribution of ionospheric small-scale irregularities from topside sounding data

This paper examines the global distribution of electron density irregularities with scales of the order of several tens to hundreds of meters in the ionosphere by using topside sounder data from the COSMOS-1809 satellite obtained in May–June and December 1987. The diffuse traces of Z-waves on topside ionograms in a frequency band just below the upper hybrid resonance are used for diagnostics. These traces are attributed to the scattering of sounder-generated ordinary and slow extraordinary mode waves.     

Pottery firing temperatures: a new method for determining the firing temperature of ceramics and burnt clay

A new method for determining the maximum firing temperature of ceramics and burnt clay is presented. The technique relies on measuring the magnetic susceptibility on a step-wise re-fired sample. The validity of the method has been tested by determining firing temperatures of two sets of clay samples fired at temperatures ranging from 400 to 1000 °C. Aliquots of the same samples have been studied petrographically by optical microscopy on thin sections and analyzed by powder X-ray diffraction in order to monitor structural and mineralogical changes as a function of temperature. The method is demonstrated on samples from four geographically widely different sites and it is applied to a larger set of ceramics of Late (ca. AD 900–AD 1450) and Inca (ca. AD 1480–AD 1532) periods from the Northwestern Argentine region, dating to a limited period of time prior to the fall of the Inca Empire. The method is shown to be a powerful tool in revealing archaeological information about the change in firing technologies in the pre-Hispanic societies in the Andean area through time.     

Starting models for the real height analysis of ionograms

Procedures are described for use in the real height analysis of ionogram data using the ordinary ray only, to allow for the presence of underlying (low density) ionisation. A controlled extrapolation of the virtual heights, with upper and lower limits, gives some useful correction under most conditions. For more accurate and consistent results a synoptic model is used to give a mean starting height at a fixed frequency of 0.5 MHz. Constraints are placed on the profile shape between 0.5 MHz and the lowest observed frequency ₁, to minimise the variations with different methods of analysis and different values of ₁. Suitable model starting heights are described for day and night conditions, and presented in tabular and graphical form. Equations are also given from which the model starting height can be calculated directly as a function of the local time, the month and the station latitude.     

Validity of the estimates of night-time meridional winds made from bottomside ionograms

Meridional wind estimated from the bottomside ionograms making use of other thermospheric and ionospheric data from a unique rocket experiment from SHAR, has been compared with the direct, in situ measurement of the same. The agreement is found to be well within the experimental errors.     

The application of a new method of Fourier Transform Infrared Spectroscopy to the analysis of burned bone

A new method of Fourier Transform Infrared Spectroscopy (FTIR) is applied to the analysis of burned bones. FTIR analyses were undertaken to examine changes in Crystallinity Index (CI), Ca/P and C/C ratios in bone experimentally burned to known, but varying, temperatures and durations. Three sample groups were used to assess the new FTIR method. Blind tests were performed to assess the use of the CI for predicting burning conditions. The results suggested that the new method of FTIR was preferable to the traditional approach, but that CI is affected by factors other than temperature of burning, including the method of FTIR used, and that predictions of burning conditions in archaeological material may not extend beyond that of ‘high’ or ‘low’ intensity of burning.     

A new statistical approach for determining the crystallinity of heat-altered bone mineral from FTIR spectra

The crystallinity of bone mineral represents an established method of measuring heat-induced change and is of importance to fields including material science, clinical science, anthropology and archaeology. A commonly used technique involves the calculation of the Crystallinity Index (CI) using selected peaks from Fourier Transform Infrared (FTIR) absorbance spectra. However, the choice of peaks has to date not been statistically justified. In this study a novel application of statistical techniques to the FTIR spectra of bone samples burned in the range 100 °C–1100 °C has been used to identify 5 new spectral indices of heat-induced crystallinity change. The validity of the new indices was tested by using a statistical classification model (LDA) to predict the burning temperature of a set of 108 bone samples burned between 100 °C and 1100 °C. A correct classification rate (CCR) of 97.2% was obtained when a combination of 4 indices including the CI was used. This was significantly better than the CCR of 66.7% which was obtained when the CI was used on its own.     

The sensitivity of D-region partial reflections to irregularity composition

D-region electron-density profiles derived from differential-absorption partial-reflection measurements may be inaccurate at heights below about 70 km, because the data analysis depends critically on the assumed composition of the scattering irregularities, which is at present uncertain. Simulated measurements show the sensitivity of the profiles to variations in the relative roles of fluctuations in electron density and electron-neutral collision frequency. Measuring differential phase in addition to amplitude may help remove the ambiguity.     

Regionalizing global trade patterns, 1981–2001: application of a new method

This paper investigates the establishment of trading regions in the global economy at the national level using a measure of trade intensity and a regional assignment algorithm that generates economically meaningful trading regions. Although there is definite regionalization in the global economy with regard to international trade, there is no evidence of an increase in the concentration of that regionalization over time. The geography of international trade is incredibly dynamic, with change related to political, historical and economic forces. Overall, trading regions have relatively few members and are increasingly a set of geographically close countries.     

NMR as a new tool for cultural heritage application: The provenance of ancient white marbles

Identifying the origin of marble used in antiquity brings back to light details of the economic, social and political organization of classical societies, and characterizing in depth the chemistry of marble is key to discovering its provenance. Beyond X‐ray diffraction, which could reveal the presence of discriminant secondary crystalline phases and the quantification of accessory minerals combined with a multivariate analysis approach, solid‐state nuclear magnetic resonance (NMR) enables one to recognize the local structure arrangement of both crystalline and amorphous materials by looking at one or more selected atoms. In present paper targets the ¹³C nuclide, and thus the major component of marble, calcium carbonate. Whatever their geological origin, marbles ¹³C‐NMR spectra present only one resonance corresponding to the carboxyl function whose intensity and line width vary from one marble to another. If the variation of the NMR signal intensity observed is the result of great T1 variations (from 220 to 5300 s) and is linked to iron content, the line width reflects defects in the calcite crystal in which calcium has been replaced by another element such as magnesium, aluminium or strontium. The specific profile of the NMR signal has been used successfully to help determine the origin of some archaeological items.     

Reconstruction of travelling ionospheric disturbances parameters by a tomographic method

A tomographic method is proposed to reconstruct parameters of the inhomogeneous ionosphere on the basis of model representations using angles of arrival or total electron content. With such an approach, determining the function of the inhomogeneous ionosphere implies finding a set of parameters of TIDs. Suitable signals can be generated by satellites.     

一种新型有机硅改性的丙烯酸树脂在加固糟朽丝织品中的应用

用加固剂加固保护已经严重糟朽的丝织品是一种延长丝织品寿命的有效方法。用一种新型有机硅改性的丙烯酸树脂SA—6对丝织品进行加固保护,结果表明SA—6在耐老化、耐沾污性、耐霉菌等方面具有优良的特性,不只是对于丝织品的保护,而且在其它类物保护中有望得到广泛应用。     

板结皮质文物回软保护新方法的研究

皮革制品在我国使用范围广泛,历史悠久,但由于其主要成分是蛋白质、脂类等有机物,容易受埋藏条件(土壤、微生物、地下水等)和馆藏环境(温湿度、光照、微生物、有害气体等)影响而产生一系列的病害(板结、虫蛀、糟朽、变形、变色、破损、缺失等),其中以板结病害最为普遍,危害较为严重。为了探究板结皮质文物的回软保护方法,以人工老化现代羊皮为样品,通过配制不同配方回软剂对其进行回软,测试皮革样品回软前后的柔软度、质量、尺寸变化数据并分析扫描电镜下的微观结构,对不同回软剂的回软效果进行对比。研究结果表明,配比为羊毛脂∶司班-80∶硅油∶水=10∶1∶1.5∶50和配比为羊毛脂∶SDBS∶硅油∶水=10∶1∶1.5∶50的回软剂对板结皮革的回软效果明显,可以在板结皮革文物的保护中推广应用。     

新型干燥剂WG-1的研制及应用

研制的WG-1干燥剂,以生石灰——氧化钙为主体,经活化剂活化处理,使其性能有了极大改善。其吸湿能力强于生石灰和硅胶,并具有良好的吸附酸性气体的能力。在高湿情况下,吸湿效果更加显。WG-1经试验测定,属无毒级,模拟试验表明,使用时对物的强度、色彩等方面不会产生任何不良影响。