Quantifying channel development and sediment transfer following chute cutoff in a wandering gravel-bed river

Three-dimensional morphological adjustment in a chute cutoff (breach) alluvial channel is quantified using Digital Elevation Model (DEM) analysis for a ca. 0.7 km reach of the River Coquet, Northumberland, UK. Following cutoff in January 1999, channel and bar topography was surveyed using a Total Station on five occasions between February 1999 and December 2000. Analysis of planform change coupled with DEM differencing elucidates channel and barform development following cutoff, and enables quantification of sediment transfers associated with morphological adjustment within the reach. This exercise indicates an initial phase of bed scour, followed by a period characterised by extensive bank erosion and lateral channel migration where erosion (including bed scour) totalled some 15,000 m³ of sediment. The channel in the post-cutoff, disequilibrium state is highly sensitive to relatively low-magnitude floods, and provision of accommodation space by bank erosion encouraged extensive lateral bar development. Bar development was further facilitated by infilling of channels abandoned by repeated within-reach avulsion and large-scale aggradation of sediment lobes deposited by higher magnitude floods. Calculations indicate that at least 6600 m³ of sediment was deposited on emerging bars within the reach over the survey period, and >2300 m³ deposited within the channel. Sediment losses from the reach may have exceeded 6500 m³.     

Assessment of seismic resistance of masonry structures including boundary conditions

The paper is devoted to the investigation of seismic response of the masonry structure and describes experiences with modelling of boundary conditions during the test of large heavy model on 6DOF shaking table. The main aim of the research was how to increase dynamic resistance capacity of old masonry buildings including the medium and strong seismic effects. The results of theoretical and numerical analyses are compared including initial forecasting calculations made before any test started. The emphasis is given to the boundary conditions reached during the excitation of the large masonry model via shaking table. Strengthening and retrofitting procedures and their effects are discussed when special fibre mortar is used for repair and strengthening of masonry parts of structure.     

Magnetic variation generated by a tangential magnetic dipole located in the Earth's core

Summary The harmonically variable magnetic field, generated by a tangential magnetic dipole (TMD), located eccentrically at the surface of the Earth's core, is investigated for various periods of time variations and for a three-layer conductivity model of the Earth. Numerical computations have shown that the field is inductively damped for variation periods of less than 500 years as compared to the field of a static TMD. It is proved that the field appropriate to the TMD, has a more complicated distribution of the Earth's surface than the field of a radial magnetic dipole. Comparison with maps of the non-dipole part of the geomagnetic field shows that the TMD is not as suitable for interpreting the observed non-dipole field and its variations as the eccentric radial magnetic dipole.     

Nutations due to higher geopotential and selenopotential harmonics

¶rt;m uu u a mauu u au u, aauau u mn n u n k a um —a—: :(n=2, k=2), (3,0), (3,1), (3,3), (4,0), (4,3); a:(2,0), (2,2), (3,1); :(2,0).

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Dedicated to RNDr Jan Pícha, CSc., on his 60th Birthday     

Radioactivity and heat production data from several boreholes in the Bohemian Massif

Summary The radiogenic heat production of rock samples from boreholes in the Bohemian Massif has been calculated from gamma-radiometric determinations of Th, U and K contents. The results, in general, fit the heat flow distribution on the territory of Czechoslovakia[1]. The values of heat production are in the range from 1.1µW m^–3 in the eastern part to 4.4µW m^–3 in the north-western part of the Bohemian Massif.     

Transformation of azimuth and zenith distance determined by satellites into geodetic reference system

Резюме Дается вывод формул разностей астрономигеского и геодезического азимутов и астрономического и геодезического зенитных расстояний с учетом членов порядка сжатия референц-эллипсоида. Учитываются также непараллельность малой оси референц-зллипсоида средней оси вращения земли и непараллельность плоскостей исходного астрономического (гриничского) и геодезического меридианов. Результирующие формулы сравниваются с классическими формулами А. А. Изотова и отмечается полное совпадение в членах, учтенных в [2]. Отмечается, что при отнесении азимутов и зенитных расстояний линий, соединяющих спутниковые станции наблюдений, в геодезическую референц-систему, следует учитывать непараллельности соответствующих референц-осей и плоскостей астрономической и геодезической систем. Отличие в сравнение с классической высшей геодезией в том, что смежные спутниковые станции могут быть удалены на весьма большие расстояния, порядка даже тысячкм.

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Dedicated to Professor Alois Zátopek on His 60th Birthday

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Address: Politickych vězňů 12, Praha 1-Nové Město.

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Address: Boční II, Praha 4-Spořilov.