1,721,035 research outputs found
INVESTIGATION OF A MATHEMATICAL MODEL ON DRAINAGE DENSITY
No full textA theoretical equation which shows the temporal change of drainage density is ex-pressed as follows;D, (t, T)=-_exp~j3~(v)_dv}(v)/~ ? exp{ 5 j3, (~) d4dvｱ1/Dswhere Di, (t, T) is the drainage density at time T on the I-th basin or geomorphic surfacewhich was formed at time t: jβi(τ) is the coefficient concerning the process which causesthe development of river at time τ:γi(τ) is the maximum drainage density at time τ andDi is the initial drainage density on the I-th geomorphic surface or basin. The equation isbased on the assumption that drainage density increases with time until it reaches thespecific upper limit, the maximum drainage density, which concerns some physical propertiesof the basin.It is possible to modify the equations into what shows the temporal change of drainagedensities in various basins or on geomorphic surfaces. The equation is;19(1, T)- exP{5>?_dr}5~p?/r?expt5 ~3(~e) d~1 dv +1/Dowith Do the initial drainage density, where it is assumed that the process is single and thephysical properties are not changed in the basins.By employing this equation, we obtain that the influence of the variation in the processto the change of the drainage density becomes smaller with time as the absolute value ofthe function concerning the process becomes larger, if we set the function is expressed asthe non-negative one where periodic variation and invariable term are combined.A theoretical equation which shows the temporal change of drainage density is ex-pressed as follows;D,(t, T)=-_exp~j3~(v)_dv}(v)/~ ? exp{ 5 j3, (~) d4dvｱ1/Dswhere Di,(t, T) is the drainage density at time T on the I-th basin or geomorphic surfacewhich was formed at time t: jβi(τ) is the coefficient concerning the process which causesthe development of river at time τ:γi(τ) is the maximum drainage density at time τ andDi is the initial drainage density on the I-th geomorphic surface or basin. The equation isbased on the assumption that drainage density increases with time until it reaches thespecific upper limit, the maximum drainage density, which concerns some physical propertiesof the basin.It is possible to modify the equations into what shows the temporal change of drainagedensities in various basins or on geomorphic surfaces. The equation is;19(1, T)- exP{5>?_dr}5~p?/r?expt5 ~3(~e) d~1 dv +1/Dowith Do the initial drainage density, where it is assumed that the process is single and thephysical properties are not changed in the basins.By employing this equation, we obtain that the influence of the variation in the processto the change of the drainage density becomes smaller with time as the absolute value ofthe function concerning the process becomes larger, if we set the function is expressed asthe non-negative one where periodic variation and invariable term are combined
ON STOCHASTIC MODEL OF RILL PATTERN
No full textDevelopment process of rills is modeled with stochastic theory.Branching process and joining process are taken into consideration.Experimental study showed that joining ratio is in proportion to the number of rills andbranching ratio is proportional to relative width (width/depth) of rills.From the above results, next equation is derived for the stochastic process of the model.dPk(t)/dt=αKPk+1(t)+βΣ Wi-1/Di Pk-1(t)-{α(k-1)+βΣ Wi-1/Di}Pk(t)for k≠1, k≠NWhere Pk(t) is the probability that the number of rills will be k at the time t. α, β arejoining coefficient and branching coefficient respectively. Wi and Di are width and depth ofI-th rill respectively.Development process of rills is modeled with stochastic theory.Branching process and joining process are taken into consideration.Experimental study showed that joining ratio is in proportion to the number of rills andbranching ratio is proportional to relative width (width/depth) of rills.From the above results, next equation is derived for the stochastic process of the model.dPk(t)/dt=αKPk+1(t)+βΣ Wi-1/Di Pk-1(t)-{α(k-1)+βΣ Wi-1/Di}Pk(t)for k≠1, k≠NWhere Pk(t) is the probability that the number of rills will be k at the time t. α,β arejoining coefficient and branching coefficient respectively. Wi and Di are width and depth ofI-th rill respectively
GEOMORPHOLOGICAL ASPECT OF LANDSLIDE AND TIME CHANGE OF RAINFALL CHARACTER IN THE SOUTH-WEST PART OF ROKKO-SAN MOUNTAINS
No full textSevere landslides at the south-west part of Rokko-san mountains in 1938, 1961 and 1967are discussed and a time series of rain fall character which concerned the landslides is analyzed.From statistical analysis of the landslides and topography in 1967, it is shown that the numberof landslides per unit area increases till the critical angel (31) as the average slope angle in thearea increases. It is also shown that the number of landslides increases till the number of 1st orderstreams and the drainage density become the critical points, 105/km2 and 15 km/km2, respectivelyand it decreases above the values.The pattern of distribution in the number or the total area of landslides does not change in theseveral decades from the data of landslides in 1938, 1961 and 1967.Annual landslide rainfall is introduced as one of the rainfall characters which is the annualsummation of excess daily rainfall which is the excess quantity over 100 mm/day. The result ofharmonic analysis for the rainfall shows that the big extrema of the harmonic function are corre-sponding to the ages when severe landslides happened and the values also correspond to the scalesof the severe landslides.Severe landslides at the south-west part of Rokko-san mountains in 1938, 1961 and 1967are discussed and a time series of rain fall character which concerned the landslides is analyzed.From statistical analysis of the landslides and topography in 1967, it is shown that the numberof landslides per unit area increases till the critical angel (31) as the average slope angle in thearea increases. It is also shown that the number of landslides increases till the number of 1st orderstreams and the drainage density become the critical points, 105/km2 and 15 km/km2, respectivelyand it decreases above the values.The pattern of distribution in the number or the total area of landslides does not change in theseveral decades from the data of landslides in 1938, 1961 and 1967.Annual landslide rainfall is introduced as one of the rainfall characters which is the annualsummation of excess daily rainfall which is the excess quantity over 100 mm/day. The result ofharmonic analysis for the rainfall shows that the big extrema of the harmonic function are corre-sponding to the ages when severe landslides happened and the values also correspond to the scalesof the severe landslides
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
THE LANDSLIDE AND ITS GEOMORPHOLOGICAL ASPECT-On the landslides in Kouchi pref. caused by heavy rain during the 5th typhoon in 1975-
No full textThe distribution of landslides in Kouchi pref. Caused by the heavy rain on Aug. 17 in 1975and the factors affecting them are discussed.Survey work showed that the collapse density (the number of collapse points per 2kmx2km)is in proportion to the gradient of slope (average gradient in the same area) till a certain criticalgradient in the A section where total rainfall is nearly constant, and in the B section where the gradi-ent is nearly constant, the collapse density is proportional to total rainfall (average total rainfallin 2kmx2km).From the results mentioned above, next equation is derived for estimating the number ofcollapse points;N(I, r)=Kir(I-io)p(r-ro)q with I=tan αwhere N(I, r): number of collapse points per unit area, Kir: coefficient, io: critical gradient foroccurrence of collapse, r: total rainfall in mm, ro: critical rainfall for occurrence of collapse inmm, α: average slope angle per unit area and p, q: constant to be determined from field data.Assuming that p and q equal 1 respectively and io equals 0 from the results obtained here, next approximate expression can be applied in practical use;N(I, r)=Kiri(r-ro).As to geomorphological aspect, the collapse density seems to be proportional to the densityof valley heads in A section.The distribution of landslides in Kouchi pref. Caused by the heavy rain on Aug. 17 in 1975and the factors affecting them are discussed.Survey work showed that the collapse density (the number of collapse points per 2kmx2km)is in proportion to the gradient of slope (average gradient in the same area) till a certain criticalgradient in the A section where total rainfall is nearly constant, and in the B section where the gradi-ent is nearly constant, the collapse density is proportional to total rainfall (average total rainfallin 2kmx2km).From the results mentioned above, next equation is derived for estimating the number ofcollapse points;N(I, r)=Kir(I-io)p(r-ro)q with I=tan αwhere N(I, r): number of collapse points per unit area, Kir: coefficient, io: critical gradient foroccurrence of collapse, r: total rainfall in mm, ro: critical rainfall for occurrence of collapse inmm, α: average slope angle per unit area and p, q: constant to be determined from field data.Assuming that p and q equal 1 respectively and io equals 0 from the results obtained here,next approximate expression can be applied in practical use;N(I,r)=Kiri(r-ro).As to geomorphological aspect, the collapse density seems to be proportional to the densityof valley heads in A section
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
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