On Some Multi-Site Multi-Season Streamflow Generation Models

The relative performance of some multi-site multi-season models is compared with respect to their adequacy for simulating monthly streamflow sequences. The three models brought under examination are the extended version of the multi-variate model proposed by Matalas (1967), the model formulated by Young and Pisano (1968), and the disaggregation model of Valencia and Schaake (1972). Computer implementation of these models has been accomplished in the form of the Multi-site Multi-season Streamflow Generation Package (MMSGP). Evaluation and comparison of the models has been carried out in terms of statistical flow parameters only. Some of these parameters are not explicitly built into the model structure. At the end, some general comments concerning applicability of each model are presented. [Since this phase of investigations was completed, Mejia and Roussele (1976) have proposed modification of the disaggregation model which will be taken into account in the further work on the MMSGP.

Interval identification of FMR parameters for spin reorientation transition in (Ga,Mn)As

In this work we report results of ferromagnetic resonance studies of a 6% 15 nm (Ga,Mn)As layer, deposited on (001)-oriented GaAs. The measurements were performed with in-plane oriented magnetic field, in the temperature range between 5K and 120K. We observe a temperature induced reorientation of the effective in-plane easy axis from [-110] to [110] direction close to the Curie temperature. The behavior of magnetization is described by anisotropy fields, H_{eff} (= 4\piM -H_{2\perp}), H_{2\parallel}, and H_{4\parallel}. In order to precisely investigate this reorientation, numerical values of anisotropy fields have been determined using powerful - but still largely unknown - interval calculations. In simulation mode this approach makes possible to find all the resonance fields for arbitrarily oriented sample, which is generally intractable analytically. In 'fitting' mode we effectively utilize full experimental information, not only those measurements performed in special, distinguished directions, to reliably estimate the values of important physical parameters as well as their uncertainties and correlations.Comment: 3 pages, 3 figures. Presented at The European Conference "Physics of Magnetism 2011" (PM'11), June 27 - July 1, 2011, Poznan, Polan

Case Studies of Seismic Energy Release Ahead of Underground Coal Mining Before Strong Tremors

We would like to test the concept that induced seismicity prior to relatively large mining tremor (ML[2.5, E[106J) can be inferred from the cumulative Benioff strain release (BSR) as power law time-to-failure before the strong event. This study presents the application of accelerating BSR prior to a large earthquake, widely used in natural seismicity, for analysis of this phenomenon in induced seismicity. The Benioff strain release is quantified as accelerated releases of cumulative (square root sum) of seismic energy in the time series. During the study, five sequences were extracted from the seismic catalogues from two Polish hard coal mines: exhausted Bobrek Mine (data form the ISEPOS Platform) and from a mine belonging to the Polish Mining Group. Next, a search radius was used to select precursory events and to indicate the type of processes occurring in the coal seam and its vicinity. The fitted power law of cumulative Benioff strain release showed changes of m-parameter. If the value of m was lower than 1.0, the process was regarded as an accelerating-like and if m was higher than 1.0—as a quiescence-like. The investigation of m-parameter vs. the search radius showed the general behaviour of the rock mass in the studied areas and allowed to evaluate the relationship between the critical radius and magnitude of the target event. The obtained scaling relation log(Rc) * 0.35 ML is similar to these reported by other authors who analysed natural seismicity which might suggest that the scaling relation works in a wide range of magnitudes

Determination of Destress Blasting Effectiveness Using Seismic Source Parameters

Underground mining of coal seams in the Upper Silesian Coal Basin is currently performed under difficult geological and mining conditions. The mining depth, dislocations (faults and folds) and mining remnants are responsible for rockburst hazard in the highest degree. This hazard can be minimized by using active rockburst prevention, where destress blastings play an important role. Destress blastings in coal seams aim to destress the local stress concentrations. These blastings are usually performed from the longwall face to decrease the stress level ahead of the longwall. An accurate estimation of active rockburst prevention effectiveness is important during mining under disadvantageous geological and mining conditions, which affect the risk of rockburst. Seismic source parameters characterize the focus of tremor, which may be useful in estimating the destress blasting effects. Investigated destress blastings were performed in coal seam no. 507 during its longwall mining in one of the coal mines in the Upper Silesian Coal Basin under difficult geological and mining conditions. The seismic source parameters of the provoked tremors were calculated. The presented preliminary investigations enable a rapid estimation of the destress blasting effectiveness using seismic source parameters, but further analysis in other geological and mining conditions with other blasting parameters is required

Application of seismic parameters for estimation of destress blasting effectiveness

Coal seams in the Upper Silesian Coal Basin are currently extracted under more and more disadvantageous geological and mining conditions. Mining depth, geological dislocations and mining remnants are factors which affect the rockburst hazard during underground mining to the greatest extent. This hazard can be minimized by employment of active rockburst prevention, where long-hole destress blasts in roof rocks (torpedo blasts) have an important role. The main goal of these blastings is to either destress local stress concentrations in rock mass and to fracture the thick layers of strong roof rocks to prevent or minimize the impact of high energy tremors on the excavations. Sometimes, these blastings are performed to make the roof rocks caving behind the longwall face easier. The efficiency of blasting is typically evaluated from the seismic effect, which is calculated based on seismic monitoring data (seismic energy) and the weight of the charged explosive. This method, as used previously in the Czech Republic, was adopted in a selected Polish hard coal mine in the Upper Silesian Coal Basin. This method enables rapid and easy estimation of destress blasting effectiveness, adjusted to conditions occurring in the designed colliery. Destress blasts effectiveness may be evaluated via the seismic source parameters analysis as well, as was carried out in the selected colliery in the Polish part of the Upper Silesian Coal Basin. These parameters provide information, for example, on its size, state of stress and occurrence of slip mechanism in the source of provoked tremors. Long-hole destress blasting effectiveness in selected colliery has been evaluated using the seismic effect method and seismic source parameters analysis. The results were compared with each other and conditions were observed in situ

An inversion of rayleigh waves dispersion curves as a tool to recognize the bedrock depth in Chorzów Stary, Poland

Identification of a bedrock beneath soft cover is one of the most important task in engineering geology. The location of boundary-overburden information may be used by investors, builders and municipal authorities to design an infrastructure or land-use plans. In such issues the application of appropriate geophysical methods is useful. However, in urban zones and areas characterized by subsurface soft layer the usage of certain methods (eg.: seismic refraction) is not advisable. The passive method of Refraction Microtremor (ReMi) can fulfill its tasks in the relatively difficult urban environment. The vertical S-wave velocity profiles were carried out as a result of inversion of Rayleigh wave dispersion curves obtained from ReMi method. The change of S-wave velocities allowed to distinguish shallow geological layers in the area of Chorzów Stary. Preliminary measurements allowed to identify the Carboniferous bedrock at a depth of 14 -18 m what has been confirmed by resistivity imaging. Furthermore, unconsolidated deposits are also recognized and the seismic results show a good correlation with the available geological information and resistivity imaging data

Wyznaczenie parametrów sprężystych płytkiego ośrodka geologicznego nad wykształcającą się niecką obniżeniową

Seismic and geodetic studies were carried out before, during, and after underground exploitation of a coal bed in Katowice – Kleofas Coal Mine, located in the Upper Silesia Coal Basin, Poland. Development of a subsidence trough was completed approximately 3 months after passage of a longwall exploitation in the coal seam. This was the time required for the subsidence trough to appear on the surface, which was confirmed by levelling measurements. Sharp changes in the elastic parameters were observed on each profile during subsidence trough development. This observation can result from changing tension and compression forces caused by increase and/or decrease of the elastic parameters of the rock mass. After completion of subsidence trough development, the rock mass appeared to return to its isotropic state and the observed changes ceased. Some minor fluctuations were noted, but they probably resulted from changes in groundwater levels, which might have affected the measured parameters

Geophysical Evaluation of Effectiveness of Blasting for Roof Caving During Longwall Mining of Coal Seam

Deep longwall mining of coal seams is made in the Upper Silesian Coal Basin (USCB) under complicated and mostly unfavourable geological and mining conditions. Usually, it is correlated with rockburst hazard mostly at a high level. One of the geological factors affecting the state of rockburst hazard is the presence of competent rocks in the roof of extracted coal seams, so rock falling behind the longwall face does not occur, and hangingup of roof rocks remains. The long-lasting absence of caving may lead to an occurrence of high-energy tremor in the vicinity of the longwall face. Roof caving behind the longwall face may be forced by blasting. The column of explosives is then located in blastholes drilled in layers of roof rocks, e.g. sandstones behind the longwall face. In this article, a characterization of tremors initiated by blasts for roof caving during underground extraction of coal seam no. 507 in one of the collieries in the USCB has been made using three independent methods. By the basic seismic effect method, the effectiveness of blasting is evaluated according to the seismic energy of incited tremors and mass of explosives used. According to this method, selected blasts gave extremely good or excellent effect. An inversion of the seismic moment tensor enables determining the processes happening in the source of tremors. In the foci of provoked tremors the slip mechanism dominated or was clearly distinguished. The expected explosion had lesser significance or was not present. By the seismic source parameters analysis, among other things, an estimation of the stress drop in the focus or its size may be determined. The stress drop in the foci of provoked tremors was in the order of 105 Pa and the source radius, according to the Brune’s model, varied from 44.3 to 64.5 m. The results of the three mentioned methods were compared with each other and observations in situ. In all cases the roof falling was forced

Spatiotemporal analysis of elastic and inelastic deformations in roof-rocks from seismological observations

The spatiotemporal analysis of seismic zones characterised by the scattering and accumulation of strain energy in the roof-rocks of the excavated longwall panel where inelastic or elastic deformations occurred during hard coal seam mining is discussed. The studied longwall panel was designed to utilize the effect of partial stress relaxation caused by the earlier extraction of the coal seams located above. A full seismic moment tensor and spectral source parameter analyses were used to obtain information about the degree of inelastic and elastic coseismic deformations. This study also showed that these deformation changes correspond to variation in the Benioff strain release characteristics. Next, analyses of deformation zones were compared with the relationship between radiated energy and the excavated volume of rocks per month. The concept of balanced seismic energy release assumed the exponential increase of released seismic energy with the increase in the volume of excavated rock. Discrepancies between the observed and predicted radiated energies indicated that strain energy in selected zones in the rock mass was either scattered if the prediction was overestimated, or accumulated if underestimated. Moreover, the study showed that elastic deformation in one zone can lead to inelastic deformation in the same zone

Performance Analysis of Dataflow Architectures Using Timed Coloured Petri Nets

We present an approach to model dataflow architectures at a high level of abstraction using timed coloured Petri nets. We specifically examine the value of Petri nets for evaluating the performance of such architectures. For this purpose we assess the value of Petri nets both as a modelling technique for dataflow architectures and as an analysis tool that yields valuable performance data for such architectures through the execution of Petri net models. Because our aim is to use the models for performance analysis, we focus on representing the timing and communication behaviour of the architecture rather than the functionality. A modular approach is used to model architectures. We identify five basic hardware building blocks from which Petri net models of dataflow architectures can be constructed. In defining the building blocks we will identify strengths and weaknesses of Petri nets for modelling dataflow architectures. A technique called folding is applied to build generic models of dataflow architectures. A timed coloured Petri net model of the Prophid dataflow architecture, which is being developed at Philips Research Laboratories, is presented. This model has been designed in the tool ExSpect. The performance of the Prophid architecture has been analysed by simulation with this model