A combined neural network/gradient‐based approach for the identification of constitutive model parameters using self‐boring pressuremeter tests

This paper presents a numerical procedure of material parameter identification for the coupled hydro‐mechanical boundary value problem (BVP) of the self‐boring pressuremeter test (SBPT) in clay. First, the neural network (NN) technique is applied to obtain an initial estimate of model parameters, taking into account the possible drainage conditions during the expansion test. This technique is used to avoid potential pitfalls related to the conventional gradient‐based optimization techniques, considered here as a corrector that improves predicted parameters. Parameter identification based on measurements obtained through the pressuremeter expansion test and two types of holding tests is illustrated on the Modified Cam clay model. NNs are trained using a set of test samples, which are generated by means of finite element simulations of SBPT. The measurements obtained through expansion and consolidation tests are normalized so that NN predictors operate independently of the testing depth. Examples of parameter determination are demonstrated on both numerical and field data. The efficiency of the combined parameter identification in terms of accuracy, effectiveness and computational effort is also discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

The significance of Chara vegetation in the precipitation of lacustrine calcium carbonate

A significant portion of calcium carbonate is deposited in lake sediments as a result of biological processes related to the photosynthetic activity of phytoplankton in the pelagic realm and, in addition, macrophytes in the littoral zone. Lake Wigry, one of the largest lakes in Poland (north‐east Poland), is characterized by: (i) carbonate sediments with a CaCO₃ content exceeding 80% within the littoral zone; and (ii) large areas of submerged vegetation dominated by charophytes (macroscopic green algae, Characeae family). It is claimed that charophytes are highly effective in utilizing HCO₃^? and forming thick CaCO₃ encrustations. Thus, this study was aimed at evaluating the CaCO₃ production by dense Chara stands overgrowing the lake bottom reaching a depth of 4 m. In late July 2009, the fresh and dry mass of plants, the percentage contribution of calcium carbonate and the production of CaCO₃ per 1 m² were investigated along three transects at three depths (1 m, 2 m and 3 m, with each sample area equal to 0·0625 m²) per transect. The composition and structure of phytoplankton and the physico‐chemical properties of the water analysed in both the littoral and pelagic zones served as the environmental background and demonstrated moderately low fertility in the lake. The greatest dry plant mass exceeded 1000 g m^?2 and CaCO₃ encrustations constituted from 59% to over 76% of the charophyte dry weight. Thus, the maximum and average values of carbonates precipitated by charophytes were 685·5 and 438 g m^?2, respectively, which exceeded previously reported results. A correlation of carbonate production with the depth of Chara stands was detected, and intermediate depths offered the most favourable conditions for carbonate precipitation (589 g m^?2 on average). As precipitated carbonates are ultimately stored in bottom deposits, the results highlight the significance of charophytes in lacustrine CaCO₃ sedimentation.     

Mortality of game mammals caused by an extreme flooding event in south-western Poland

We examine mortality in five terrestrial species of game animals resulting from an extreme flood event in Central Europe in July 1997. We present species-specific mortality rates and collate them with local abundances to show the susceptibilities of the different species to flood mortality. We also compare mortality rates in areas inundated by the main river and by its tributaries. Data were collected in the catchment area of the Odra River, south-western Poland. Mortality was estimated by surveying for drowned animals in flooded areas of 50 hunting districts (2,876 km²). Total mortality amounted to 3,613 individuals, mostly of roe deer Capreolus capreolus and brown hare Lepus europaeus. Relative to estimates of abundance, mortality was disproportionately high in hares. Drownings of roe deer and wild boar, Sus scrofa were proportional to local abundance. Young individuals were particularly affected. Mortality was low in foxes, Vulpes vulpes, and red deer, Cervus elaphus. The mortality rate increased with the proportion of area flooded and the duration of flooding and was four times higher along the Odra River than along its tributaries. Our data specify, for the first time, direct losses in wild, large animals in response to an extreme flood event. Despite high overall losses, negative long-term effects on populations seemed unlikely. Nevertheless, to lessen the impact, river management focused primarily on human safety should also integrate the needs of wildlife.     

The influence of precipitation intensity growth on the urban drainage systems designing

For 50 years of long observation period (1960–2009), on a high level of statistical significance (95 %), a decreasing trend of annual precipitation amounts and an increasing trend of the number of rainy days during the year (64 %) were found. For the seasonal changes (V–X), similarly, there was found a statistically significant (94 %) decreasing precipitation amount trend and an increasing trend of the number of rainy days (50 %). As far as the intensity of maximum precipitation is concerned, a very statistically significant increasing trend (95 %) was found. Taking as the basis, the model for a trend, defined for the period of 1960–2009, the increase of weighted average interval values of maximum precipitation amounts (h?≥?0.75?t ^0.5) in the year 2059 was estimated to be about 26 %, in comparison with the starting year 1960. An increasing trend of maximum precipitation frequency in Wroc?aw was also proved. To a safe sewerage systems designing in Wroc?aw according to current standards (EN 752 2008; DWA-A118 2006), the precipitation frequency to the simulations of excessive accumulation occurrences to the land level should be changed.     

Non-integrability of the dumbbell and point mass problem

This paper discusses a constrained gravitational three-body problem with two of the point masses separated by a massless inflexible rod to form a dumbbell. This problem is a simplification of a problem of a symmetric rigid body and a point mass, and has numerous applications in Celestial Mechanics and Astrodynamics. The non-integrability of this system is proven. This was achieved thanks to an analysis of variational equations along a certain particular solution and an investigation of their differential Galois group. Nowadays this approach is the most effective tool for study integrability of Hamiltonian and non-Hamiltonian systems.     

The strength and width of Fe Kα lines in Seyferts and their correlations with the X-ray slope

We study properties of Fe K lines of a large sample of Seyfert 1s observed by ASCA . Fits with power laws and Gaussian lines yield the average linewidth and equivalent width of 0.22±0.03 keV and 0.13±0.01 keV, respectively. Thus, the typical lines are weak and narrow. We then obtain the average line profile of all our spectra, and find it to consist of a narrow core and blue and red wings, with the red wing being much weaker than that of e.g. MCG −6-30-15. We obtain three average spectra of Seyferts grouped according to the hardness, and find the equivalent width of the core (originating in a remote medium) to be ≃50 eV in all three cases. The wings are well fitted by a broad line from a disc with strong relativistic effects. Its equivalent width correlates with the slope, increasing from ∼70 eV for the hardest spectrum to ∼120 eV for the softest one. The inner disc radius decreases correspondingly from ∼40 to ∼10 gravitational radii, and the fitted disc inclination is ∼45°. The obtained correlation between the slope and the strength of the broad Fe K line is found to be consistent with the previously found correlation of the slope and Compton reflection.     

Radon-222 in medicinal groundwaters of Szczawno Zdrój (Sudety Mountains, SW Poland)

 Radon is a significant component of the groundwaters that discharge in the springs of Szczawno Zdrój and are recognized as medicinal. However, among the five exploited springs adjoining each other, it is only in Marta Spring that radon occurs in large concentrations (up to 325.6 Bq/dm³). Therefore, the authors have made an attempt to describe and clarify this fact. They found out from their own research and archival data that ²²²Rn dissolves in the waters of Marta Spring after acidulous waters of deep circulation have mixed with poorly mineralized shallow waters in their outflow zone. The genesis of the gas is determined by the content of its parent nuclide, ²²⁶Ra, in the sandstones in the vicinity of the intake. The volume of the rocks providing radon to the waters of this intake has been estimated at several hundred cubic metres. No seasonal fluctuations in radon concentration have been observed and ²²²Rn concentration changes do not seem to be influenced by changes in the concentration of other chemical components of the waters or by the discharge of the intake. The process of dissolving ²²²Rn in the medicinal groundwaters of Marta Spring is the last, the shortest, and the most local of the processes that form the chemical composition and the physical properties of these waters. Received: 7 January 2000 · Accepted: 12 August 2000     

Estimation of earthquake hazard parameters for incomplete and uncertain data files

The maximum likelihood estimation of earthquake hazard parameters (maximum regional magnitudem _max, activity rate , and theb parameter in the Gutenberg-Richter distribution) is extended to the cases of incomplete and uncertain data. The method accepts mixed data containing only large (extreme) events and a variable quality of complete data with different threshold magnitude values. Uncertainty of earthquake magnitude is specified by two values, the lower and upper magnitude limits. It is assumed that such an interval contains the real unknown magnitude. The proposed approach allows the combination of different quality catalog parts, e.g. those where the assignment of magnitude is questionable and those with magnitudes precisely determined.As an illustration of the method, the seismic hazard analysis for western Norway and adjacent sea area (4–8°E, 58–64°N) is presented on the basis of the strongest earthquakes felt during the period 1831–1889 and three complete catalog parts, covering the period 1890–1987.Paper presented at the 21st General Assembly of the European Seismological Commission held in Sofia, 1988.On leave from Institute of Geophysics, Polish Academy of Sciences, Warsaw, Poland.     

Darss Sill as a biological border in the fossil record of the Baltic Sea: evidence from diatoms

Biostratigraphical and palaeoecological analyses of cores along a transect from Femer Belt to the Arkona Basin reveal that North Sea waters began to enter the western Baltic Sea between 8600 and 8400 calibrated years BP. Studies of diatoms indicate that Mecklenburg Bay was characterised by slightly brackish-water conditions between 8400 and 8000 cal. years BP. At around 8000 cal. years BP increasing salinity is indicated by a strong dominance of the diatoms Paralia sulcata and Dimeregramma minor. Some centuries later another diatom assemblage appeared and became dominant in Mecklenburg Bay. This assemblage includes Hyalinella lateripunctata and Pravifusus hyalinus species typical of shallow water areas along the Atlantic coast today. At this time the first marine molluscs made their appearance. The oldest shell of a marine mollusc found in our material is dated to 7600 cal. years BP. The associated assemblage that includes adult specimens of the gastropod Aporrhais pespelicani indicates higher salinities than today.During the Littorina Sea stage a marine diatom flora with P. sulcata, Catenula adhaerens and D. minor crossed the Darss Sill and became widely distributed in the Arkona Basin, Pomeranian Bay and the Baltic Sea proper. In contrast, taxa indicative of the Hyalinella lateripunctata/P. hyalinus assemblage are only found west of the Darss Sill in Femer Belt and Mecklenburg Bay. Apparently, the Darss Sill threshold has been acting as an important salinity border from around 7800 cal. years BP until today.     

Point-to-curve ray tracing

Point-to-curve ray tracing is an attempt at dealing with multiplicity of solutions to a generic boundary-value problem of ray tracing. In a point-to-curve tracing (P2C) the input parameters of the boundary-value problem (BVP), such as the ends of the ray, are allowed to vary along a curve. The solutions of the BVP automatically wander from one solution branch to another generating a nearly complete multi-valued solution of the BVPs.A procedure for transforming an arbitrary iterative algorithm, solving a ray tracing BVP to a corresponding P2C algorithm, is presented. Bifurcations of the solution curve of the P2C problem at caustics are studied and an algorithm for obtaining the bifurcating branches is developed. In particular, transition from real rays to complex rays in a caustic shadow offers an additional link between otherwise disconnected solution curves of the P2C problem. The topological structure of a generic solution curve and its implications for the algorithm are studied.