117,339 research outputs found
The Geomorphological Origin of Recession Curves
No full textThis study is motivated by the fact that natural basins share some striking similarities in their basic organization as well as in the way they respond to rainfall input. The central objective here is thus to link the patterns observed in morphology of basins with the patterns that we observe in their hydrologic responses. This study particularly attempts to uncover hidden links between basin morphology and recession curves through a simple conceptual model describing dynamics of saturated channel network or active drainage network (ADN).
Analysis of recession curves is performed by following the framework proposed in the paper by Brutsaert and Neiber, i. e. to interpret –dQ/dt as having a power law relationship with Q (-dQ/dt = kQα), where Q is the discharge at the outlet of a basin at time t. It is shown here that N(l), number of links in a channel network at distance l from their channel heads exhibits a power law relationship with G (l), length of the ADN or length of the channel network at a distance greater than or equal to l from channel heads. And by assuming that the rate of discharge produced by the AND per unit length, q, and the rate at which channel network desaturates towards downstream, c, are constant in space and time, it is argued here that the power law relationship between –d/dt and Q essentially originates from the power law relationship bewteen N(l) and G(l).
It is observed that there is no unique relationship between –dQ/dt and Q for a basin, which implies, the popular assumption that there exists a unique relationship between storage and discharge of a basin is wrong. Also a typical –dQ/dt vs Q curve possess different regimes, because of its association with flood response that we observe shortly after rainfall and observational errors that particularly dominate during very low flow periods. One can observe a fairly good power law relationship between –dQ/dt vs Q, shortly after a rainfall event, continuing for several days. This regime for each individual hydrograph is identified by means of visual interpretation. The power law exponent α for each individual hydrograph of a basin is then computed and the median value is considered as the representing α for the basin . A good agreement is observed between the observed power law exponents, α0, with the geomorphic power law exponents, αg, for 67 United States basins of different sizes and situated in different climatic zones. The correlation is strong, particularly, for the steep basins without having significant human influences, like the presence of dams, cities, extensive agriculture practice etc. Also it is found that the power law exponent α is closely related to the well known Hack’s exponent .
The coefficient k is observed to have power law relationship with any characteristics discharge chosen deonated as Qn, which objectively means the discharge observed after n days of a hydrograph peak. Therefore, one can make different recession curves of a basin collapse on one another by using a suitable multiplicative function. Also it is observed that the power law exponent, γ, as well as the coefficient of determination increases as n increases. Thus the collapse gets more prominent with increase in n.
N(l)/A vs G(l)/A graphs of different basins are found to be collapsing on another, implying that natural basins follow some universal geomorphological themes. Recession curves on the other hand are dependent on many factors like geology, land use, topographic characteristics. It is observed that the recession curves of the basins that have similar geological and topographical characteristics collapse on one another. This observation essentially implies that one can classify natural basins by just observing their recession curves.
This finding further strengthens the assumptions of constant q and constant c made earlier. And finally, it is stressed that the argument, recession curves bearing signatures of basin morphology, can be safely stretched to conclude that the incision of the channel network may be due, to a significant degree, to subsurface flow, in such a way as produce an approximately uniform drainage of the local groundwater system and thus a uniform distribution of q.Questo studio è motivato dal fatto che i bacini naturali sono accomunati da importanti similarità relativamente alla loro organizzazione ed al modo in cui essi rispondono agli impulsi di pioggia. L’obiettivo centrale di questa tesi è quindi quello di individuare una relazione tra alcune caratteristiche osservabili nella morfologia dei bacini e la loro risposta idrologica. In particolare con questo studio si cerca di scoprire analogie nascoste tra la morfologia dei bacini e le curve di recessione attraverso un semplice modello concettuale in grado di descrivere le dinamiche delle reti in saturazione o “Active Drainage Networks” (ADN).
L’analisi delle curve di recessione è effettuata seguendo un approccio proposto in Brutsaert and Neiber (1977), in cui -dQ/dt è rappresentato in funzione di Q attraverso una legge di potenza (-dQ/dt = k Qα), dove Q è il deflusso alla sezione di chiusura di un bacino al tempo t. Nella tesi si mostra che il numero di connessioni (links) in una rete, N(l), ad una distanza l dalle origini (channel heads) è correlato attraverso una legge di potenza con la lunghezza della ADN, cioè la lunghezza delle connessioni ad una distanza maggiore o uguale ad l dalle origini. Assumendo che il deflusso, q , prodotto dalla ADN per unità di lunghezza e la velocità di desaturazione della rete, c, siano costanti nel tempo e nello spazio si discute l’ipotesi che la legge di potenza che lega -dQ/dt e Q abbia origine dalla legge di potenza che lega N(l) e G(l).
Si osserva che non c’è un'unica relazione tra -dQ/dt e Q per un bacino, il che suggerisce che la nota assunzione di una singola relazione tra deflusso e volume di immagazzinamento sia inappropriata. Inoltre, una tipica curva -dQ/dt vs. Q possiede regimi differenti dovuti al suo legame con la risposta superficiale che si osserva subito dopo un evento di pioggia e agli errori di misura effettuati in particolare in periodi di deflusso moderato. Si può osservare una relazione di potenza discretamente buona tra -dQ/dt e Q subito dopo un evento di pioggia e persistente per diversi giorni. L’esponente α della legge di potenza per ciascun idrogramma di un bacino è quindi calcolato e il valore mediano è considerato rappresentativo di tutti i valori di α per il bacino. I valori osservati dell’esponente αo sono in buon accordo con gli esponenti della relazione geomorfologica, αg, per 67 bacini statunitensi di dimensioni diverse e situati in diverse zone climatiche. In particolare si osserva una forte correlazione per bacini con elevata pendenza che non presentano aspetti antropici significativi, come ad esempio dighe, città, diffuse aree coltivate, ecc. Si è inoltre osservato che l’esponente α è significativamente correlato con il noto esponente di Hack.
Si è visto che il coefficiente k è legato attraverso una legge di potenza con qualsiasi deflusso caratteristico selezionato: k=k’Qn-γ, dove Qn è il deflusso osservato dopo n giorni dal picco dell’idrogramma. Di conseguenza, diverse curve di recessione possono essere fatte collassare in un’unica curva. Si osserva inoltre che l’esponente γ della legge di potenza e il coefficiente di determinazione aumentano all’aumentare di n.
Si osserva come le curve N(l)/A vs. G(l)/A di diversi bacini collassino in un'unica curva, il che implica che i bacini naturali seguono una qualche legge geomorfologica universale. Le curve di recessione, invece, dipendono da molti fattori come la geologia, l’uso del suolo, le caratteristiche topografiche. Si osserva che le curve di recessione di bacini con simili caratteristiche topografiche e geologiche collassano in un’unica curva. Questa osservazione implica che è possibile classificare bacini naturali solo sulla base delle curve di recessione. Questa scoperta rafforza ulteriormente l’assunzione di q e c costanti fatta in precedenza. Infine viene messo in evidenza che il fatto che le curve di recessione rappresentano una sorta di “firma” della morfologia dei bacini suggerisce che il deflusso subsuperficiale influenza la rete, in modo da produrre un drenaggio approssimativamente uniforme, e perciò una distribuzione uniforme di q
Huttonella L. Pfeiffer 1856
No full textSubgenus Huttonella L. Pfeiffer, 1856 Ennea (Huttonella) L. Pfeiffer, 1856: 174. Gulella (Huttonella) — Zilch, 1960: 570. Huttonella — Schileyko, 2000: 821. Type species. Pupa bicolor Hutton, 1834, by subsequent designation (Nevill, 1878: 6). Remarks. The type species of Huttonella has a pantropical distribution (Berry, 1965; Simone, 2013), and it probably originated from Asia (Naggs, 1989; Rowson & Herbert, 2016). Molecular phylogeny showed that it is closely related to “true” Gulella L. Pfeiffer, 1856 (Rowson et al., 2010), and it was treated as a subgenus of Gulella in the most recent revision (Rowson & Herbert, 2016).Published as part of Páll-Gergely, Barna, Hunyadi, András, Grego, Jozef, Sajan, Sheikh, Tripathy, Basudev & Chen, Zhe-Yu, 2020, A review of the Diapheridae (Gastropoda: Eupulmonata: Streptaxoidea), with special emphasis on India and Myanmar, pp. 682-718 in Raffles Bulletin of Zoology 68 on page 712, DOI: 10.26107/RBZ-2020-0083, http://zenodo.org/record/534976
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Square Dancing with the Stars to Enhance Dynamic Hirschman Linkages?
No full textIn this Presidential Address, the author takes the reader on a reconnaissance of his life and time as a regional scientist. He points out scenery he found scintillating along the way, hoping that some may pick up the banner and chew on a few of the ideas for a while. He suggests a revisit to Albert O. Hirschman’s notion of key sectors and more empirical analysis related to Marcus Berliant’s and Masahisa Fujita’s notion of knowledge creation and transfer.Presidential Address, San Antonio, Texas, March 29, 2014 (53rd Meetings of the Southern Regional Science Association
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Letter from unknown writer to Jesse L. Boyce
No full textLetter to Jesse L. Boyce from unknown author (possibly Jack) about the investigation into the powder magazine located in the Grand Canyon. Some personal news is included in the letter such as the writer's marriage to the daughter of C.A. Taylor, former Supervisor of Cochise County
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Sarah L. Blum Author Visit - Warrior Nurse: PTSD and Healing
No full textHear Sarah L. Blum, author of Women Under Fire: Abuse in the Military, discuss her newest book, Warrior Nurse: PTSD and Healing followed by a Q&A and book signing.
Sarah L. Blum is a decorated Vietnam veteran who served as an operating room nurse during the intense fighting of 1967. In recognition of her service, she was awarded the Army Commendation Medal.
Sponsored by CWU Veterans Center and CWU Libraries.https://digitalcommons.cwu.edu/libraryevents/1252/thumbnail.jp
Lillian L. Lambert, Author, Speaker, and Entrepreneur
No full textLillian L. Lambert, Author, Speaker, and Entrepreneu
Letter to Alfred L. Shoemaker, February 10, 1948
No full textA handwritten letter from an unknown author addressed to Alfred L. Shoemaker, dated February 10, 1948. Within, the author discusses the Pennsylvania Dutch word for Ash Wednesday, along with traditions associated with this day.https://digitalcommons.ursinus.edu/shoemaker_documents/1118/thumbnail.jp
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