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Start Over Coverage 51-59

2. Equations for predicting interrill erosion on steep slopes in the Three Gorges Reservoir, China

Creator:
Feng, Qian, Linyao, Dong, Jigen, Liu, Bei, Sun, Honghu, Liu , Jiesheng, Huang , and Hao, Li
Format:
počítač and online zdroj
Type:
model:article and TEXT
Subject:
purple soil, interrill erosion rate, rainfall intensity, slope gradient, and hydraulic parameter
Language:
Slovak
Description:
The Three Gorges Reservoir region suffers from severe soil erosion that leads to serious soil degradation and eutrophication. Interrill erosion models are commonly used in developing soil erosion control measures. Laboratory simulation experiments were conducted to investigate the relationship between interrill erosion rate and three commonly hydraulic parameters (flow velocity V, shear stress τ and stream power W). The slope gradients ranged from 17.6% to 36.4%, and the rainfall intensities varied from 0.6 to 2.54 mm·min–1. The results showed that surface runoff volume and soil loss rates varied greatly with the change of slope and rainfall intensity. Surface runoff accounted for 67.2–85.4% of the precipitation on average. Soil loss rates increased with increases of rainfall intensity and slope gradient, Regression analysis showed that interrill erosion rate could be calculated by a linear function of V and W. Predictions based on V (R2 = 0.843, ME = 0.843) and W (R2 = 0.862, ME = 0.862) were powerful. τ (R2 = 0.721, ME = 0.721) did not seem to be a good predictor for interrill erosion rates. Five ordinarily interrill erosion models were analyzed, the accuracy of the models in predicting soil loss rate was: Model 3 (ME = 0.977) > Model 4 (ME = 0.966) > Model 5 (ME = 0.963) > Model 2 (ME = 0.923) > Model 1 (ME = 0.852). The interrill erodibility used in the model 3 (WEPP) was calculated as 0.332×106 kg·s·m–4. The results can improve the precision of interrill erosion estimation on purple soil slopes in the Three Gorges Reservoir area.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

3. Invariant approximation for fuzzy nonexpansive mappings

Creator:
Beg, Ismat and Abbas, Mujahid
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
fuzzy normed space, strictly convex fuzzy normed space, fixed point, fuzzy nonexpansive mapping, fuzzy best approximation, and fuzzy Banach mapping
Language:
English
Description:
We establish results on invariant approximation for fuzzy nonexpansive mappings defined on fuzzy metric spaces. As an application a result on the best approximation as a fixed point in a fuzzy normed space is obtained. We also define the strictly convex fuzzy normed space and obtain a necessary condition for the set of all t-best approximations to contain a fixed point of arbitrary mappings. A result regarding the existence of an invariant point for a pair of commuting mappings on a fuzzy metric space is proved. Our results extend, generalize and unify various known results in the existing literature.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

4. Occurrence of selected organochlorine pesticide residues in surface sediments from the Velke Kozmalovce, Ruzin, and Zemplinsk Sirava water reservoirs, Slovakia

Creator:
Hiller, Edgar, Sirotiak, Maroš, Tatarková, Veronika, and Jurkovič, Ľubomír
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
organochlorine pesticides, DDT, surface sediments, water reservoir, organic matter, organochlórované pesticídy, dnové sedimenty, vodná nádrž, and organická hmota
Language:
Slovak
Description:
Surface sediment samples from three water reservoirs of Slovakia were analyzed for selected organochlorine pesticides (OCPs). Concentrations of total dichlorodiphenyltrichloroethanes (ΣDDTs) in the sediments from Velke Kozmalovce, Ruzin, and Zemplinska Sirava ranged from 12 to 24 ng g-1, 5 to 28 ng g-1, and 1 to 20 ng g-1, respectively, with the exception of one sediment sample from Zemplinska Sirava, having anomalously high concentration of ΣDDTs (526 ng g-1). Concentrations of hexachlorobenzene (HCB) in the sediments from these water reservoirs were generally lower and ranged from 0.3 to 9 ng g-1. Other organochlorine pesticides such as mirex, lindane and heptachlor were not detected in the surface sediments. Ratios of DDT/(DDE + DDD) were lower than 1.0 in majority of the sediment samples indicating that the degradation of the parent DDT occurred significantly and DDT in the sediments from the studied water reservoirs was derived mainly from the weathered agricultural soils. Moreover, ratios of DDD/DDE indicated that the parent DDT was degraded under aerobic conditions before depositing into the sediments of these water reservoirs. and V štúdii boli analyzované vzorky sedimentov z troch vodných nádrží Slovenska na vybrané organochlórované pesticídy (OCPs). Koncentrácie sumy DDT a jeho metabolitov DDE a DDD (ΣDDTs) v sedimentoch z vodných nádrží Veľké Kozmálovce, Ružín a Zemplínska Šírava sa nachádzali v intervale od 12 do 24 ng g-1, od 5 do 28 ng g-1 a od 1 do 20 ng g-1, s výnimkou jednej vzorky sedimentu zo Zemplínskej Šíravy, ktorá vykazovala anomálne vysokú koncentráciu ΣDDTs (526 ng g-1). Koncentrácie hexachlórbenzénu (HCB) v sedimentoch z týchto vodných nádrží boli všeobecne nižšie a pohybovali sa v intervale od 0,3 do 9 ng g-1. Iné v sedimentoch sledované organochlórované pesticídy ako mirex, lindán a heptachlór neboli zistené. Vo väčšine vzoriek sedimentov boli hodnoty pomeru DDT/(DDE + DDD) nižšie ako 1, z čoho sa dá usúdiť, že väčšia časť pôvodne prítomného DDT sa rozložila na jeho hlavné metabolity a že DDT v sedimentoch vodných nádrží pochádza najmä z erodovaných poľnohospodárskych pôd. Hodnoty pomeru DDD/DDE ukázali, že predtým ako bol DDT deponovaný do sedimentov vodných nádrží, rozkladal sa najmä za aeróbnych podmienok.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

5. On the Euler function of repdigits

Creator:
Luca, Florian
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
Euler function, prime, and divisor
Language:
English
Description:
For a positive integer $n$ we write $\phi (n)$ for the Euler function of $n$. In this note, we show that if $b>1$ is a fixed positive integer, then the equation \[ \phi \Big (x\frac{b^n-1}{b-1}\Big )=y\frac{b^m-1}{b-1},\qquad {\text{where}} \ x,~y\in \lbrace 1,\ldots ,b-1\rbrace , \] has only finitely many positive integer solutions $(x,y,m,n)$.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public