Reproductive variability in North Sea plaice, sole, and cod   总被引：4，自引：1，他引：4  

Rijnsdorp  A. D.; Daan  N.; van Beek  F. A.; Heessen  H. J. L. 《ICES Journal of Marine Science》1991,47(3):352-375

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Improving communication from managers to fishers in Europe and the US     

van Densen  Wim L. T.; McCay  Bonnie J. 《ICES Journal of Marine Science》2007,64(4):811-817

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Measurement of the signal to noise ratio in seismic profiling     

Kees Rutten  Mathée Valeton  Theo van Grunsven 《Marine Geophysical Researches》1972,1(4):445-450

The measurement of the signal to noise ratio in continuous seismic profiling systems is carried out by means of a small general purpose digital computer equipped with an analog to digital converter. The computer is programmed to compute and compare the power spectrum of a sample of noise to the power spectrum of a sample of noise plus an echo. Power spectra of some twenty to fifty shots are averaged to yield reliable estimates of the signal to noise ratio as a function of frequency. The observed spectra agree well with spectra calculated from signals measured near to an air-gun. This measurement of signal to noise ratio as a function of frequency provides unambiguous information for the adjustment of the necessary band-pass filter thus improving the operation of a continuous seismic profiler.  相似文献   

Twelve years of tracking 52-Hz whale calls from a unique source in the North Pacific     

William A. Watkins  Mary Ann Daher  Joseph E. George  David Rodriguez 《Deep Sea Research Part I: Oceanographic Research Papers》2004,51(12):1889-1901

A unique whale call with 50–52 Hz emphasis from a single source has been tracked over 12 years in the central and eastern North Pacific. These calls, referred to as 52-Hz calls, were monitored and analyzed from acoustic data recorded by hydrophones of the US Navy Sound Surveillance System (SOSUS) and other arrays. The calls were noticed first in 1989, and have been detected and tracked since 1992. No other calls with similar characteristics have been identified in the acoustic data from any hydrophone system in the North Pacific basin. Only one series of these 52-Hz calls has been recorded at a time, with no call overlap, suggesting that a single whale produced the calls. The calls were recorded from August to February with most in December and January. The species producing these calls is unknown. The tracks of the 52-Hz whale were different each year, and varied in length from 708 to 11,062 km with travel speeds ranging from 0.7 to 3.8 km/h. Tracks included (A) meandering over short ranges, (B) predominantly west-to-east movement, and (C) mostly north-to-south travel. These tracks consistently appeared to be unrelated to the presence or movement of other whale species (blue, fin and humpback) monitored year-round with the same hydrophones.  相似文献   

GPS signal acquisition using the repeatability of successive code phase measurements     

Zhen Zhu  Frank van Graas  Janusz Starzyk 《GPS Solutions》2008,12(1):43-53

This paper introduces a new method for GPS signal acquisition, which is based on the repeatability of successive code phase measurements and the M-of-N search algorithm. The performance of the proposed method in terms of probability of signal detection is similar to that of traditional methods, except that the calculation of the probability of detection does not rely on the noise distribution or the Carrier-to-Noise ratio (C/N₀). The code phase repeatability-based method is presented along with equations for probability of detection and probability of false detection. If the distribution of the noise is known, it also provides an estimate of the C/N₀. The proposed method is illustrated for coherent and non-coherent acquisition and C/N₀ estimation.  相似文献   

Comparison of dissolved and particulate arsenic distributions in shallow aquifers of Chakdaha, India, and Araihazar, Bangladesh     

Jerome Métral  Laurent Charlet  Sara Bureau  Sukumar Basu Mallik  Sudipta Chakraborty  Kazi M Ahmed  MW Rahman  Zhongqi Cheng  Alexander van Geen 《Geochemical transactions》2008,9(1):1

Background  

The origin of the spatial variability of dissolved As concentrations in shallow aquifers of the Bengal Basin remains poorly understood. To address this, we compare here transects of simultaneously-collected groundwater and aquifer solids perpendicular to the banks of the Hooghly River in Chakdaha, India, and the Old Brahmaputra River in Araihazar, Bangladesh.  相似文献   

Cu 2p absorption spectroscopy as a probe for the site occupancy of (ZnxCu1−x)WO4 solid solution     

P. F. Schofield  C. M. B. Henderson  S. A. T. Redfern  G. van der Laan 《Physics and Chemistry of Minerals》1993,20(6):375-381

The solid solution sanmartinite (ZnWO₄)—cuproscheelite (CuWO₄) has been studied using Cu 2p X-ray absorption spectroscopy. While a single L₃ absorption peak is observed for CuWO₄, two distinct L₃ absorption peaks with a separation of ～0.8 eV are observed for the intermediate samples in the solid solution. The two peaks represent distinct Cu sites: one with all CuO₆ next nearest neighbours in the (Cu,Zn)O₆ chains, another having at least one ZnO₆ next nearest neighbour. Both sites show a linear increase in covalency as a function of increasing Cu-content. The relative intensities of the two absorption peaks is dependent upon the Cu-content and has been used to model the site occupancies. The results reveal that the local structural effects can be associated with a composition-dependent structural phase transition from P2/c (ZnWO₄) to P $\bar 1$ (CuWO₄). Deviations from a single-site model are explained in terms of the local environments, and evidence for site preferences and local clustering are explored.  相似文献   

A plan for a new generation 2M-class telescope in Indonesia     

Karel A. van der Hucht 《Astrophysics and Space Science》1984,99(1-2):409-410

One of the prime astrophysical interests of the Observatorium Bosscha is, and has always been, double star research: visual double star research with the double-60 cm Zeiss telescope (dedicated in 1928), and theoretical research of evolved massive spectroscopic binaries (since 1972). For one thing, this is the very reason that this IAU Colloquium No. 80, celebrating the 60th anniversary of the Observatorium Bosscha in Lembang, is devoted to binary astrophysics.Up to now, visual, photographic, and photometric tools have been used for binary research at the Observatorium Bosscha. An important, essential additional tool for binary research is spectrographic equipment, in order to measure radial velocities of binary components.Therefore, we suggest to make a plan for a new modern telescope, a reflector with a primary mirror of about 2 m in diameter and with a modern spectrograph/detector combination for radial velocity measurements.At a number of major astronomical observatories scientists have been considerating to erect new telescopes devoted primarily to radial velocity measurements. The reason for this is that at the end of this decade the parallax and proper motion measurements to be made by the ESA astrometric satellite Hipparcos will become available of more than 100 000 single stars and double stars. At that time there will be a compelling need for radial velocity measurements of all these stars to complement the parallax and proper motion measurements. With the combination of this data enormous progress will be made in double star research, and in the study of galactic dynamics, another topic of interest of the Observatorium Bosscha. If it could be realized to build such a dedicated radial velocity telescope in Indonesia, Indonesian astronomers could take a leading role in this field of research.Without going into technical details, we would like to emphasize here that such a new instrument should be a trueNew Generation Telescope, and that the Institut Teknologi Bandung should participate from the very beginning in its design, construction and assembling, and the subsequent servicing; ITB could participate in the field of optics, mechanics, and electronics. Modern astronomy offers tremendous challenges to technology, which are of great interest to technological institutes. The new telescope should be computer controlled, and the spectrograph should have a modern digital read-out (Reticon, IPCS, or CCD). The telescope should have one of those recently becoming availablethin mirrors, allowing more mechanical freedom. It could be a telescope with a siderostat which feeds the light into a fixed telescope, thus improving both the stability of the telescope and that of the spectrograph. In this way the staff and students of ITB, as well as the technical staff of the Observatorium Bosscha will be drawn into modern techniques of many varieties. And for ITB such an enterprise may even have a spin-off into other fields than astronomy.One aspect which is of great importance for the new telescope is the selection of its site. The present site of the Observatorium Bosscha in Lembang is a good one, but for a new modern telescope one wants to make sure that it is going to be located at the most ideal site.Therefore an Indonesian site-survey should be initiated promptly. Site survey equipment is available at many big observatories and could be borrowed. The site survey should extend over at least 4–5 years to monitor the meteorological and environmental situation at many sites.In the meantime the design and fund rainsing can be considered. Modern day astronomy depends on financial support from governments and inter-governmental organizations. Therefore it is urged that a proposal for a new telescope as indicated above clearly describes the advantages of such a new telescope both for astrophysical research in Indonesia, and for the introduction of new technologies in Indonesian technological institutes.The recently formed Steering Committee for Indonesian-Netherlands Astrophysics (INA) is willing to explore the possibilities for this plan. We hope that after investigating the interest of ITB in this matter, a proposal could be made before the end of this year.Paper presented at the Lembang-Bamberg IAU Colloquium No. 80 on Double Stars: Physical Properties and Generic Relations, held at Bandung, Indonesia 3–7 June, 1983.  相似文献   

Geology of the lunar farside crater Necho   总被引：1，自引：0，他引：1  

Ann W. Gifford  Ted A. Maxwell  Farouk El-Baz 《Earth, Moon, and Planets》1979,21(1):25-42

The lunar farside crater Necho (30 km diameter) displays intricate morphological and structural characteristics. The highland setting provides a complex impact site when compared with the relatively uniform setting of mare craters. Therefore, the effects of pre-impact topography and structure play a dominant role in Necho's formation and modification. Necho's bright ejecta, extensive rays, fresh morphology, and lack of superposed craters indicate that it is extremely young. The asymmetric distribution of ejecta materials may be due to substrate effects, topographic shalowing, or oblique impact.Necho's interior is divided into five physiographic units based on morphologic differences: three floor units (Necho does not display a true flat floor), one hilly central unit, and the wall unit which includes terraces and smooth walls. The interior of the crater also exhibits an unusual asymmetry in the prevalence of terraced units on the western wall. Interior morphology and terrace orientations are probably the result of pre-impact effects. Structural and topographic orientations associated with three large pre-existing degraded craters dominate the impact site.  相似文献   

High-density CO2−N2 inclusions in eclogite-facies metasediments of the Münchberg gneiss complex,SE Germany     

R. Klemd  A. M. van den Kerkhof  E. E. Horn 《Contributions to Mineralogy and Petrology》1992,111(3):409-419

The eclogite-facies metasedimentary rocks in the Münchberg gneiss complex (T=630±30° C/P17–24 kbar) locally contain CO₂–N₂-rich fluid inclusions of extremely low molar volumes (32 cm³/mol) in quartz. These fluid compositions are mainly found in rocks intercalated with calcsilicate bands. Densities were determined from low-temperature phase transitions like stable or metastable homogenization (L+VL), partial homogenization (S+L+VS+L) and the transition S+LL (L = liquid, V = vapour, S = solid). The high fluid densities are in agreement with eclogite-facies pressure and temperature and subsequent amphibolite facies. CO₂–N₂ inclusions were not observed in adjacent eclogites nor in non-calcareous metasediments. These rock types contain predominantly H₂O-rich inclusions correlating with amphibolite-facies conditions. The variation of fluid composition with lithological differences indicates local fluid gradients and speaks against a pervasive fluid flow during eclogite-facies metamorphism.  相似文献