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1.
On the origins of part-time radio pulsars 总被引:1,自引:0,他引:1
Bing Zhang Janusz Gil Jaroslaw Dyks 《Monthly notices of the Royal Astronomical Society》2007,374(3):1103-1107
2.
We study the concept of radius-to-frequency mapping using a geometrical method for the estimation of pulsar emission altitudes. The semi-empirical relationship proposed by Kijak &38; Gil is examined over three decades of radio frequency. It is argued that the emission region in a millisecond pulsar occupies the magnetosphere over a distance of up to about 30 per cent of the light-cylinder radius, and that in a normal pulsar occupies up to approximately 10 per cent of the light-cylinder radius. 相似文献
3.
Adam P. Piotrowski Maciej J. Napiorkowski Jaroslaw J. Napiorkowski Marzena Osuch Zbigniew W. Kundzewicz 《水文科学杂志》2017,62(4):606-625
In recent years sampling approaches have been used more widely than optimization algorithms to find parameters of conceptual rainfall–runoff models, but the difficulty of calibration of such models remains in dispute. The problem of finding a set of optimal parameters for conceptual rainfall–runoff models is interpreted differently in various studies, ranging from simple to relatively complex and difficult. In many papers, it is claimed that novel calibration approaches, so-called metaheuristics, outperform the older ones when applied to this task, but contradictory opinions are also plentiful. The present study aims at calibration of two simple lumped conceptual hydrological models, HBV and GR4J, by means of a large number of metaheuristic algorithms. The tests are performed on four catchments located in regions with relatively similar climatic conditions, but on different continents. The comparison shows that, although parameters found may somehow differ, the performance criteria achieved with simple lumped models calibrated by various metaheuristics are very similar and differences are insignificant from the hydrological point of view. However, occasionally some algorithms find slightly better solutions than those found by the vast majority of methods. This means that the problem of calibration of simple lumped HBV or GR4J models may be deceptive from the optimization perspective, as the vast majority of algorithms that follow a common evolutionary principle of survival of the fittest lead to sub-optimal solutions. 相似文献
4.
Identifying slope processes over time and their imprint in soils of medium‐high mountains of Central Europe (the Karkonosze Mountains,Poland) 下载免费PDF全文
Jaroslaw Waroszewski Markus Egli Dagmar Brandová Marcus Christl Cezary Kabala Malgorzata Malkiewicz Jakub Kierczak Bartłomiej Glina Paweł Jezierski 《地球表面变化过程与地形》2018,43(6):1195-1212
Soils in mountainous areas are often polygenetic, developed in slope covers that relate to glacial and periglacial activities of the Pleistocene and Holocene and reflect climatic variations. Landscape development during the Holocene may have been influenced by erosion/solifluction that often started after the Holocene climatic optimum. To trace back soil evolution and its timing, we applied a multi‐methodological approach. This approach helped us to outline scenario of soil transformation. According to our results, some aeolian input must have occurred in the late Pleistocene. During that time and the early Holocene, the soils most likely had features of Cryosols or Leptosols. Physico‐chemical and mineralogical analyses have indicated that the material was denudated (between late Boreal to the Atlantic) from the ridge and upper‐slope positions forming a colluvium at mid‐slope positions. Later, during the Sub‐Boreal, mass wasting of the remains of silt material deposited at the end of the Pleistocene age on the ridge top seems to have occurred. In addition, the cool and moist conditions caused the deposition of a colluvium at the lower‐slope positions. The next phase was characterized by the transformation of Leptosols/Cambisols into Podzols at upper‐slope or shoulder positions and to Albic Cambisols at mid‐slope positions. During the Sub‐Boreal period, Stagnosols started to form at the lower part of the slope catena. Overall, the highest erosion rates were calculated at the upper‐slope position and the lowest rates at mid‐slope sites. Berylium‐10 (10Be) data showed that the Bs, BC/C were covered during the Holocene by a colluvium with a different geological composition which complicated the calculation of erosion or accumulation rates. The interpretation of erosion and accumulation rates in such multi‐layered materials may, therefore, be hampered. However, the multi‐methodological reconstruction we applied shed light on the soil and landscape evolution of the eastern Karkonosze Mountains. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
5.
Adam P. Piotrowski Jaroslaw J. Napiorkowski Marzena Osuch Maciej J. Napiorkowski 《水文科学杂志》2013,58(10):1903-1925
ABSTRACTArtificial neural networks (ANNs) become widely used for runoff forecasting in numerous studies. Usually classical gradient-based methods are applied in ANN training and a single ANN model is used. To improve the modelling performance, in some papers ensemble aggregation approaches are used whilst in others, novel training methods are proposed. In this study, the usefulness of both concepts is analysed. First, the applicability of a large number of population-based metaheuristics to ANN training for runoff forecasting is tested on data collected from four catchments, namely upper Annapolis (Nova Scotia, Canada), Biala Tarnowska (Poland), upper Allier (France) and Axe Creek (Victoria, Australia). Then, the importance of the search for novel training methods is compared with the importance of the use of a very simple ANN ensemble aggregation approach. It is shown that although some metaheuristics may slightly outperform the classical gradient-based Levenberg-Marquardt algorithm for a specific catchment, none performs better for the majority of the tested ones. One may also point out a few metaheuristics that do not suit ANN training at all. On the other hand, application of even the simplest ensemble aggregation approach clearly improves the results when the ensemble members are trained by any suitable algorithms.
EDITOR D. Koutsoyiannis; ASSOCIATE EDITOR E. Toth 相似文献
6.
Szymon Gburek Janusz Sylwester Miroslaw Kowalinski Jaroslaw Bakala Zbigniew Kordylewski Piotr Podgorski Stefan Plocieniak Marek Siarkowski Barbara Sylwester Witold Trzebinski Sergey V. Kuzin Andrey A. Pertsov Yurij D. Kotov Frantisek Farnik Fabio Reale Kenneth J. H. Phillips 《Solar physics》2013,283(2):631-649
Solar Photometer in X-rays (SphinX) was a spectrophotometer developed to observe the Sun in soft X-rays. The instrument observed in the energy range ≈?1?–?15 keV with resolution ≈?0.4 keV. SphinX was flown on the Russian CORONAS–PHOTON satellite placed inside the TESIS EUV and X telescope assembly. The spacecraft launch took place on 30 January 2009 at 13:30 UT at the Plesetsk Cosmodrome in Russia. The SphinX experiment mission began a couple of weeks later on 20 February 2009 when the first telemetry dumps were received. The mission ended nine months later on 29 November 2009 when data transmission was terminated. SphinX provided an excellent set of observations during very low solar activity. This was indeed the period in which solar activity dropped to the lowest level observed in X-rays ever. The SphinX instrument design, construction, and operation principle are described. Information on SphinX data repositories, dissemination methods, format, and calibration is given together with general recommendations for data users. Scientific research areas in which SphinX data find application are reviewed. 相似文献
7.
Adam P. Piotrowski Jaroslaw J. Napiorkowski Pawel M. Rowinski Steve G. Wallis 《水文科学杂志》2013,58(5):883-894
Abstract In order to predict the impact of pollution incidents on rivers, it is necessary to predict the dispersion coefficient and the flow velocity corresponding to the discharge in the river of interest. This paper explores methods for doing this, particularly with a view to applications on ungauged rivers, i.e. those for which little hydraulic or morphometric data are available. An approach based on neural networks, trained on a wide-ranging database of optimized parameter values from tracer experiments and corresponding physical variables assembled for American and European rivers, is proposed. Tests using independent cases showed that the neural networks generally gave more reliable parameter estimates than a second-order polynomial regression approach. The quality of predictions of temporal concentration profiles was heavily influenced by the accuracy of the velocity prediction. Citation Piotrowski, A. P., Napiorkowski, J. J., Rowinski, P. M. & Wallis, S. G. (2011) Evaluation of temporal concentration profiles for ungauged rivers following pollution incidents. Hydrol. Sci. J. 56(5), 883–894. 相似文献
8.
Climate Change Impact on Hydrological Extremes: Preliminary Results from the Polish-Norwegian Project 总被引:2,自引:1,他引:1
Renata J. Romanowicz Ewa Bogdanowicz Sisay E. Debele Joanna Doroszkiewicz Hege Hisdal Deborah Lawrence Hadush K. Meresa Jaroslaw J. Napiórkowski Marzena Osuch Witold G. Strupczewski Donna Wilson Wai Kwok Wong 《Acta Geophysica》2016,64(2):477-509
This paper presents the background, objectives, and preliminary outcomes from the first year of activities of the Polish–Norwegian project CHIHE (Climate Change Impact on Hydrological Extremes). The project aims to estimate the influence of climate changes on extreme river flows (low and high) and to evaluate the impact on the frequency of occurrence of hydrological extremes. Eight “twinned” catchments in Poland and Norway serve as case studies. We present the procedures of the catchment selection applied in Norway and Poland and a database consisting of near-natural ten Polish and eight Norwegian catchments constructed for the purpose of climate impact assessment. Climate projections for selected catchments are described and compared with observations of temperature and precipitation available for the reference period. Future changes based on those projections are analysed and assessed for two periods, the near future (2021–2050) and the far-future (2071–2100). The results indicate increases in precipitation and temperature in the periods and regions studied both in Poland and Norway. 相似文献
9.
James C.I. Dooge Witold G. Strupczewski Jaroslaw J. Napiórkowski 《Journal of Hydrology》1982,54(4):371-387
The St. Vénant equations for unsteady flow in open channels and the Muskingum method are written both in their conventional forms and in the state-space formulation. The hydrodynamic equation of motion is solved by the method of state trajectory variation and the result for the first-order variation in the state-space variables is used as a basis of linking the parameters of the Muskingum model with the hydraulic parameters of the open channel reach. The results are applicable to any shape of cross-section and to any type of friction law. 相似文献
10.
Karin Högdahl Jaroslaw Majka Håkan Sjöström Katarina Persson Nilsson Stefan Claesson Patrik Konečný 《Contributions to Mineralogy and Petrology》2012,163(1):167-188
Monazite in melt-producing, poly-metamorphic terranes can grow, dissolve or reprecipitate at different stages during orogenic
evolution particularly in hot, slowly cooling orogens such as the Svecofennian. Owing to the high heat flow in such orogens,
small variations in pressure, temperature or deformation intensity may promote a mineral reaction. Monazite in diatexites
and leucogranites from two Svecofennian domains yields older, coeval and younger U–Pb SIMS and EMP ages than zircon from the
same rock. As zircon precipitated during the melt-bearing stage, its U–Pb ages reflect the timing of peak metamorphism, which
is associated with partial melting and leucogranite formation. In one of the domains, the Granite and Diatexite Belt, zircon
ages range between 1.87 and 1.86 Ga, whereas monazite yields two distinct double peaks at 1.87–1.86 and 1.82–1.80 Ga. The
younger double peak is related to monazite growth or reprecipitation during subsolidus conditions associated with deformation
along late-orogenic shear zones. Magmatic monazite in leucogranite records systematic variations in composition and age during
growth that can be directly linked to Th/U ratios and preferential growth sites of zircon, reflecting the transition from
melt to melt crystallisation of the magma. In the adjacent Ljusdal Domain, peak metamorphism in amphibolite facies occurred
at 1.83–1.82 Ga as given by both zircon and monazite chronology. Pre-partial melting, 1.85 Ga contact metamorphic monazite
is preserved, in spite of the high-grade overprint. By combining structural analysis, petrography and monazite and zircon
geochronology, a metamorphic terrane boundary has been identified. It is concluded that the boundary formed by crustal shortening
accommodated by major thrusting. 相似文献