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1.
Giovanni?Pugliano Umberto?RobustelliEmail authorView authors OrcID profile Fabio?Rossi Raffaele?Santamaria 《GPS Solutions》2016,20(3):499-508
Multipath remains one of the major challenges in Global Navigation Satellite System (GNSS) positioning because it is considered the dominant source of ranging errors, which can be classified into specular and diffuse types. We present a new method using wavelets to extract the pseudorange multipath in the time domain and breaking it down into the two components. The main idea is an analysis-reconstruction approach based on application of both continuous wavelet transform (CWT) and discrete wavelet transform (DWT). The proposed procedure involves the use of L1 code-minus-carrier (CMC) observable where higher-frequency terms are isolated as residuals. CMC residuals are analyzed by applying the CWT, and we propose the scalogram as a technique for discerning time–frequency variations of the multipath signal. Unlike Fourier transform, the potential of the CWT scalogram for examining the non-stationary and multifrequency nature of the multipath is confirmed as it simultaneously allows fine detection and time localization of the most representative frequencies of the signal. This interpretation of the CWT scalogram is relevant when choosing the levels of reconstruction with DWT, allowing accurate time domain extraction of both the specular and diffuse multipath. The performance and robustness of the method and its boundary applicability are assessed. The experiment was carried out using a receiver of Campania GNSS Network. The results are given in which specular multipath error is achieved using DWT level 7 approximation component and diffuse multipath error is achieved using DWT level 6 denoised detail component. 相似文献
2.
The concentrations of PCBs and DDT at the surface of sediments of rivers in the Canton of Geneva were examined. Concentration variations observed along the rivers are discussed. In the case of the Rhône River, recent pollution at the surface of sediments is compared with that of aged underlying layers. 相似文献
3.
Some turbiditic measures carried out by a limnological diffusiometer along with the physico-chemical determinations of the
Lake of Neuchatel have permitted to subdivide the water column in 4 distinct layers: the Epilimnium, the Clear Water Layer,
the Pelagic Nepheloid Layer and the Benthic Nepheloid Layer.
相似文献
4.
Par S. Dolédec 《Aquatic Sciences - Research Across Boundaries》1987,49(1):29-41
A study of the thermal regime of the Lower Ardeche River was carried out from July 1982 to December 1984 using a chemical
method (sucrose inversion) and a continuous temperature recorder. Yearly, monthly and daily temperature fluctuations were
analyzed. The main factors that influence thermal variations are air temperature and geomorphology of the canyon. The hydrological
regime is responsible of the water temperature fluctuations between years Despite the low winter temperatures, the Lower Ardeche
can be classified among Mediterranean rivers, which typically have a very high maximum in summer.
相似文献
5.
Dr Par Olivier L. Reymond 《Aquatic Sciences - Research Across Boundaries》1983,45(2):405-408
A method allowing isolation of phytoplancton algae for unialgal cultures is briefly described. Advantages and limits of the method are discussed. 相似文献
6.
Jean-Pierre Par Bargetzi 《Aquatic Sciences - Research Across Boundaries》1960,22(2):641-758
Sans résumé
Travail réalisé avec l’appui du Fonds national suisse de la Recherche.
La rédaction du présent travail est antérieure au mémoire deDottrens [254]3). La parution du texte de cet auteur a très exactement co?ncidé avec la présentation de notre thèse. Ces deux recherches
ont été accomplies indépendamment. D’après les conclusions deDottrens, les Corégones du lac de Neuchatel doivent désormais être désignés par
Le mot ?ichtyologie? et les termes de la même famille sont orthographiés avec un seul ?h? en accord avec une décision récente
de l’Académie. 相似文献
7.
P. Par Mercier 《Aquatic Sciences - Research Across Boundaries》1957,19(2):613-623
Conclusion Par ce qui précède, on se rend compte que chaque lac constitue un cas particulier qui doit être étudié pour lui-même et que
l'aération artificielle d'un lac de grandes dimensions est susceptible d'être réalisée.
A notre époque les lacs prennent de plus en plus d'importance comme réservoirs pouvant servir à l'alimentation en eau potable.
Pour remplir ce r?le il est indispensable que la qualité de l'eau soit satisfaisante afin d'éviter des traitements co?teux.
On peut dire que l'aération artificielle, malgré le co?t initial des installations et la consommation annuelle d'énergie électrique,
est le procédé le plus économique pour améliorer l'eau d'un lac eutrophe.
Actuellement la consommation de l'eau augmente partout et dépasse parfois dans certaines agglomérations 1000l/habitant/par
jour. Dans ces conditions les frais d'exploitation d'une station d'aération conjuguée avec un service important de distribution
d'eau ne grèvent le prix de revient du mètre cube que d'un supplément minime. Il est évident que l'emploi de l'aération artificielle
pour assainir un lac ne dispense pas de combattre les causes originelles de la pollution des eaux. C'est un procédé auxiliaire
précieux qui peut aider un lac à rétablir son équilibre biologique compromis par les conséquences de l'eutrophie.
Cet article résume les idées exposées par l'auteur à l'occasion d'un colloque organisé à Zurich le 22 février 1957 par le
Prof.Jaag, président de la Commission hydrobiologique de la Société helvétique des sciences naturelles. 相似文献
8.
In order to establish the magnetic carriers and assess the reliability of previous paleomagnetic results obtained for Eocene marine marls from the south Pyrenean basin, we carried out a combined paleo- and rock-magnetic study of the Pamplona-Arguis Formation, which crops out in the western sector of the southern Pyrenees (N Spain). The unblocking temperatures suggest that the characteristic remanent magnetization (ChRM) is carried by magnetite and iron sulphides. The ChRM has both normal and reversed polarities regardless of whether it resides in magnetite or iron sulphides, and represents a primary Eocene magnetization acquired before folding. Rock magnetic results confirm the presence of magnetite and smaller amounts of magnetic iron sulphides, most likely pyrrhotite, in all the studied samples. Framboidal pyrite is ubiquitous in the marls and suggests that iron sulphides formed during early diagenesis under sulphate-reducing conditions. ChRM directions carried by magnetic iron sulphides are consistent with those recorded by magnetite. These observations suggest that magnetic iron sulphides carry a chemical remanent magnetization that coexists with a remanence residing in detrital magnetite. We suggest that the south Pyrenean Eocene marls are suitable for magnetostratigraphic and tectonic purposes but not for studies of polarity transitions, secular variations and geomagnetic excursions, because it is difficult to test for short time differences in remanence lock-in time for the two minerals. The presence of iron sulphide minerals contributing to the primary magnetization in Eocene marine marls reinforces the idea that these minerals can persist over long periods of time in the geological record. 相似文献
9.
Reconstructing the Neogene-Quaternary biostratigraphy in continental environments and recognising ‘boundaries’ between successive mammalian faunal complexes is a problematic task. The definition and application of biochronology has been often tainted by references to and inferences from biostratigraphy. Actually, the discontinuities in the continental sedimentary record, environmental conditions, taphonomic and sampling biases are responsible for the fact that the stratigraphical order of the lowest and highest occurrences of fossil remains (stratigraphic datum) does not necessarily reflect the temporal order of actual first/last appearances of taxa (palaeobiological events) in time. Nonetheless, the first/last appearance bioevents (recorded by lowest/highest occurrences of fossil remains in fossiliferous levels of different continental stratigraphical successions) have been the principal foundation for establishing the biochronological setting of continental mammal faunas. Therefore, from a theoretical point of view, ‘boundaries’ should be defined by the oldest and/or youngest ‘historical occurrence’ of one or more taxa. What about an operational approach?Some examples of the Italian faunas are presented, focusing on the transition from the Villafranchian to the Galerian and from the Galerian to the Aurelian Land-Mammal Ages. The results obtained indicate the difficulty of defining a stable scheme that can be applied for correlation by the international scientific community. 相似文献
10.
Par Marjan Čadež 《Pure and Applied Geophysics》1965,61(1):232-245
Summary In the paper it is shown in which manner the cooling of the air due to the melting of snowflakes causes the appearance of special air masses of greater or smaller dimensions. Here some examples are given of the formation of such air masses of melting in Yugoslavia on the north slopes of the Dinarian Alps.
Zusammenfassung In dieser Arbeit ist gezeigt, auf welche Weise die Abkühlung der Luft, die durch das Schmelzen der Schneeflocken bedingt ist, besondere Luftmassen von grösseren und kleineren Ausdehnungen zur Folge hat. Es sind einige Beispiele von solchen Luftmassen des Schmelzens in Jugoslawien gegeben, die auf der Nordseite der dynarischen Gebirge formiert sind.相似文献