How friends share urban space: An exploratory spatiotemporal analysis using mobile phone data

This study proposes a framework to investigate the roles of urban spaces in connecting social contacts (i.e., “friends”). The framework is applied to a Call Detail Record (CDR) dataset collected in Singapore. First, a comparative analysis is performed to understand how friends share urban space differently from random people. Then, we derive two metrics to quantify the “bonding” and “bridging” capabilities of places in the city. The two metrics reflect the potential of a place in connecting friends and random people (e.g., chance encounters), respectively. Finally, we examine the temporal signature of the places’ bonding capabilities, and associate the results with various types of Points of Interest (POIs). We find that: (1) friends are more likely to share urban space than random people, and they also share more locations; (2) a place could play different roles in connecting friends vs. random people, and the relationship (between bonding and bridging) varies depending on the time and type of a day (weekdays vs. weekends); (3) the temporal signature of bonding capability is strongly related to the semantics of a place; (4) certain POI types (e.g., shopping malls) tend to have a much higher impact on bonding capability than others (e.g., sports centers).     

Modeling flood event characteristics using D-vine structures

The authors investigate the use of drawable (D-)vine structures to model the dependences existing among the main characteristics of a flood event, i.e., flood volume, flood peak, duration, and peak time. Firstly, different three- and four-dimensional probability distributions were built considering all the permutations of the conditioning variables. The Frank copula was used to model the dependence of each pair of variables. Then, the appropriate D-vine structures were selected using information criteria and a goodness-of-fit test. The influence of varying the data length on the selected D-vine structure was also investigated. Finally, flood event characteristics were simulated using the four-dimensional D-vine structure.     

Variations of trace elements and rare earth elements (REEs) treated by two different methods for snow-pit samples on the Qinghai-Tibetan Plateau and their implications

Although previous investigations of the trace elements in snow and ice from the Qinghai-Tibetan Plateau obtained interesting information about pollution from human activities on the plateau, most were based on traditional acidification methods. To emphasize the influence of the different sample-preparation methods on the records of trace elements and rare earth elements, snow samples were collected from glaciers on the Qinghai-Tibetan Plateau in China and prepared using two methods: traditional acidification and total digestion. Concentrations of 18 trace elements (Al, Ti, Fe, Rb, Sr, Ba, V, Cr, Mn, Li, Cu, Co, Mo, Cs, Sb, Pb, Tl, and U), along with 14 rare earth elements (REEs: La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu), Y, and Th in the snow samples, were measured using inductively coupled plasma-sector field mass spectrometry (ICP-SFMS). The results showed that the mass fraction of the trace elements (defined as ratio of concentration in the acid-leachable fraction to that in the digested sample) such as Mo, Ti, Al, Rb, and V, varied from 0.06 to 0.5. The mass fraction of other trace elements varied from about 0.6 to more than 0.9; those of the REEs, Y, and Th varied from 0.34 to 0.75. Lower mass fractions will lead to an overestimated contribution of other sources, especially human activities, and the underestimated fluxes of these trace elements (especially REEs, Y, and Th, as well as dust) if the REEs are used as the proxy for the crust dust. The two sample-preparation methods exhibited different REE normalized distribution patterns, REE ratios, and provenance-tracing results. The REE normalized distribution patterns and proxies in the digested samples are more reliable and integrated than those found in traditional acidification method for dust-provenance tracing.     

Can Rock Composition Affect Sublittoral Epibenthic Communities?

Abstract. Biomineralogy, as the complex of interactions at different levels (cell, organism, species, and community) between organisms and minerals, may play a significant role in the spatial distribution and structure of marine communities. For instance, a negative influence of quartz has been underlined on the Mediterranean benthic communities, which show a species-poorer structure in quartz-rich environments. Excluding the role of quartz, the aim of this work is to verify whether the composition of various mineralogical substrata can affect a hard-bottom benthic community. In the Ligurian Sea, the Levanto area shows an astonishing complex of substrata with different petrographic characters: in a few kilometres, sandstones, serpentinites, gabbros, and basalts occur in geometric association. Consequently, this area represents a suitable frame for this type of study. Herein, algal photophilic assemblages growing on the four mineralogical substrata show significant differences in number of species and percentage cover or abundance. This suggests a significant influence of rock mineral composition on the hard bottom community. Therefore, rock composition must be taken into account for a better understanding of the processes at the basis of hard-bottom community development and diversity.     

Sull'utilizzabilità a scopo geofisico delle relazioni fra anomalie Eötvössiane e magnetiche

Riassunto Viene mostrato come sia possibile dare pratiche applicazioni alle formule diEötvös sulle relazioni fra anomalie gravimetriche e magnetiche, in modo da ricavare le proprietà magnetiche delle rocce che causano l'anomalia. Da ciò l'opportunità di eseguire sempre unitamente a misurazioni con la bilancia di torsione anche misure magnetiche.

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Summary It is shown how is possible to give pratical applications toEötvös' formulas on relations between gravitational and magnetic anomalies, in such a way as to obtain informations on magnetic properties of rocks that cause the anomaly. It follows the opportunity of executing together with torsion balance measures, in as much as possible, also magnetic measurements.

     

Trasformazioni con mezzi ottico-meccanici fra le proiezioni cartografiche della sfera

Riassunto I. Premesso che l'analizzatore differenziale diBush è adattabile alla costruzione di funzioni di due variabili, si studiano alcuni strumenti che, applicati all'analizzatore, permettono di eseguire varie transformazioni fra le proiezioni cartografiche della sfera, espresse in forma esplicita. In particolare si esaminano le transformazioni fra le proiezioni cilindriche e coniche. — II. Rilevati gliinconvenienti che comporta l'impiego di soli mezzi meccanici, si introducono dispositivi ottico-meccanici che restringono il campo delle transformazioni, ma le rendono, praticamente effettuabili. Detti dispositivi vengono applicati, oltre alle transformazioni citate, anche per ottenere la equivalente sinusoidale a paralleli rettilinei e circolari.

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Summary I. The Differential Analyser ofBush, being fit for the construction of two variables functions, some instruments are studied which, applied to the Analyser, allow several transformations between cartographic projections of the sphere, expressed in explicit form, to be executed. Particularly, transformations between cylindrical and conical projections are examined. — II. After having revealed the failures produced by the use of mechanical means only, optic-mechanical devices are introduced, which restrain the range of transformations but make them practically effectible. Such devices are applied, besides the previous transformations, also to obtain the sinusoidal equivalent in rectilinear and circular parallels.

     

Sulla costante fondamentale della formula ellissoidica internazionale per la gravita' normale

Riassunto Sulla base soprattutto delle numerose misure di gravità successive al 1930, dei nuovi valori compensati per le stazioni di riferimento e con opportune ipotesi per ridurre al minimo le cause di errore, che vengono esaminate e discusse, si procede al calcolo dig _e nelle due ipotesi diBouguer ed isostatica (h_c=–113,7 km). Il risultato è 978,043 nel sistema di Potsdam.

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Summary Principally, on the base of the numerous measures of gravity established after 1930, and of the new compensated values for the reference stations, and with suitable hypothesis to reduce to a minimum the causes of error, which are examined and discussed, it is calculated the value ofg _e in the two hypothesis ofBouguer and isostatical (h _c =–113,7 km). The result is 978,043 in Potsdam System.

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Zusammenfassung Auf Grund vor allem der zahlreichen nach 1930 ausgeführten Schweremessungen, der neuen kompensierten Werte fur die Hauptstationen, und durch geeignete Hypothesen um die Fehlerursachen, welche geprüft und erötert werden, zu reduzieren, wird esg _e in den beiden Hypothesen vonBouguer und der Isostasie (h _c =–113,7 km) berechnet. Das Resultat ist 978,043 im Potsdamer System.

     

Per un sistema di riferimento «internazionale» delle misure di gravita' nota preliminare

Riassunto Il presente lavoro si prefigge lo scopo di esporre il problema del sistema di riferimento per le misure di gravità relativa e di mostrare che il valore base «convenzionale» di Potsdam (981.274), considerato fino a pochi anni addietro come uno dei risultati di maggiore precisione, si presenta invece affetto molto probabilmente da un notevole errore. Ciò viene dimostrato principalmente dalla nuova misura assoluta al Nat. Bureau of Standards di Washington, e sembra essere confermato anche dalla misura assoluta di Leaingrado, di cui non ci sono ancora noti i risultati definitive. — Si propone perciò l'adozione di un nuovo sistema di riferimento «internazionale», basato cioè non più sul risultato di una sola misura assoluta della gravità, ma sulle più importanti finora eseguite. Le differenze relative fra di esse risultano da una nuova compensazione della rete internazionale delle stazioni di riferimento eseguita dall'A. — Saremo molto grati a tutti quei Geodeti che vorranno cortesemente iniziare la discussione su questo problema.

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Summary It is shown that the «conventional» base-value of gravity at Potsdam (981, 274), considered until few years ago as one of the more precisious results, is instead affected very probably by a big error. This is demonstred first by the new absolute measure at Washington, and seems to be confirmed by the absolute measure at Leningrad too, for which definitive results are not yet known. — A new «international» reference system is therefore proposed, based no more on only one absolute measure of gravity, but on the most important ones until now executed. The relative differences between them result from a new compensation of the international net of the reference-stations excuted from the Author. — We shall be very thankfull to all those Geodesists who will kindly begun the discussion on this problem for its definitive solution.

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Zusammenfassung Es wird gezeigt, dass der grundlegende konventionelle Referenzwert für relative Schweremessungen (Potsdam –981,274), der bis vor einigen Jahren als einer der genauesten Resultate bezeichnet wurde, von einem bemerkenden Fehler wahrscheinlich behaftet wird. Das wird vor allem durch die neue absolute Schweremessung von Washington gezeigt und scheint auch durch die absolute Schweremessung von Leningrad bestätigt zu werden, von der uns noch die endgültigen Resultaten fehlen. — Es wird daher die Verwendung eines neuen «internationalen» Referenz-Systems vorgeschlagen, das sich nicht mehr allein auf einer einzigen absoluten Schweremessung stützt, sondern auf den Wichtigsten die bisher ausgeführt wurden Die relativen Unterschiede entstammen aus einer neuen Ausgleichung des internationalen Netzes alle Hauptstationen, die von dem Verfasser ausgeführt wurde. — Wir werden alle Geodäten bedanken, welche die Diskussion dieser Frage freundlich beginnen möchten zur Erlangung seiner endgültigen Lösung.

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Resumé Ce travail a le but d'exposer le plus clairement possible le problème du système de référence pour les mesures de gravité rélative et de montrer que la valeur fondamentale «conventionnelle» de Potsdam (981,274), considerée il y a quelques années comme un des résultats de la plus grande précision, se présent au contraire frappée très probablement d'une faute considérable. Tout cela est démontré surtout par la nouvelle mesure absolue faite à Washington et il semble être confirmé même par la mesure absolue de Leningrad, dont nous ne connaissons pas encore les résultats définitifs. — C'est pour cela que nous proposons l'adoption d'un nouveau système de référence international, qui soit fondé non plus sur le résultat d'une seule mesure absolue de la gravité, mais sur les plus importantes effectuées jusqu'ici. Les différences rélatives entr'elles resultent d'une nouvelle compensation du reseau international des stations de référence executée par l'Auteur. — Nous serons bien grès à tous ces Géodésiens qui voudront bien commencer la discussion sur ce problème, pur sa résolution définitive.

     

Anomalie magnetiche e declinazione in quota in Italia con speciale riguardo per la navigazione aerea strumentale

Riassunto Con i procedimenti del Malkin, verificati sperimentalmente dal Ramsayer, viene intrapreso lo studio dell'influsso sulla declinazione in quota di alcune anomalie magnetiche in Italia, per cui esistono rilievi di dettaglio nella componente verticale (Colli Euganei, Stromboli). Per le zone anomale, capaci di influenzare il mantenimento della rotta nella navigazione aerea con la bussola, vengono proposte carte speciali con l'andamento delle isogone a varie quote fondamentali, di cui si presenta un saggio per l'isola di Stromboli. Attraverso un esame delle anomalie magnetiche in Italia, si indicano le zone di probabile e quelle di sicuro pericolo per la navigazione aerea con la bussola finchè non si potrà costruire per esse carte del tipo proposto. Per il rimanente spazio aereo italiano si prospetta l'opportunità che le isogone per i piloti siano costruite sulla base del campo normale.

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Summary Applying the proceedings of Malkin verified by experiments of Ramsayer is studied the influence on the declination in upper levels of some magnetic anomalies in Italy, for which exist detailed reliefs in the vertical component (Colli Euganei, Stromboli). For the anomalous zones capable to influence the maintaining of the route in compass-airnavigation special maps are proposed containing the position of the isogons at various fondamental heights, an instance of which is presented for the isle of Stromboli. An examination of the magnetic anomalies in Italy shows the zones of probable and those of secure danger for compass-airnavigation as long as it will not be possible to prepare maps in the proposed type. For the rest of the Italian air-space the opportunity is prospected to construct the isogons for the pilots on the basis of the normal field.

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Zusammenfassung Nach dem Malkinschen Verfahren wird der Einfluss einiger magnetischer Störgebiete (Colli Euganei, Stromboli) auf die Flugnavigation berechnet. Es wird vorgeschlagen, wo nötig, spezielle Deklinationskarten mit den Isogonen zu verschiedenen Haupthöhen vorzubereiten; ein Beispiel hiefür wird für die Insel Stromboli gegeben. Die Störgebiete, welche eine Gefahr für die Flugnavigation mit dem Magnetkompass bilden können, werden für Italien begrenzt. In dem übrigen Raum in Italien wird als das beste Verfahren für die Flugnavigation vorgeschlagen, die Isogonen nach dem vom Verf. berechneten Normalfeld darzustellen.