scholarly journals Dynamics of Spatial Logistic Model: Finite Systems

Author(s):  
Yuri Kozitsky
2019 ◽  
Vol 10 (1) ◽  
pp. 21-28
Author(s):  
Aniela Bălăcescu ◽  
Radu Șerban Zaharia

Abstract Tourist services represent a category of services in which the inseparability of production and consumption, the inability to be storable, the immateriality, and last but not least non-durability, induces in tourism management a number of peculiarities and difficulties. Under these circumstances the development of medium-term strategies involves long-term studies regarding on the one hand the developments and characteristics of the demand, and on the other hand the tourist potential analysis at regional and local level. Although in the past 20 years there has been tremendous growth of on-line booking made by household users, the tour operators agencies as well as those with sales activity continue to offer the specific services for a large number of tourists, that number, in the case of domestic tourism, increased by 1.6 times in case of the tour operators and by 4.44 times in case of the agencies with sales activity. At the same time, there have been changes in the preferences of tourists regarding their holiday destinations in Romania. Started on these considerations, paper based on a logistic model, examines the evolution of the probabilities and scores corresponding to the way the Romanian tourists spend their holidays on the types of tourism agencies, actions and tourist areas in Romania.


2003 ◽  
Vol 39 (9) ◽  
pp. 749 ◽  
Author(s):  
E. Miranda ◽  
A. Cester ◽  
A. Paccagnella

2021 ◽  
Vol 25 (1) ◽  
pp. 2156759X2110186
Author(s):  
Emily Sallee ◽  
Kok-Mun Ng ◽  
Abraham Cazares-Cervantes

Despite the growing epidemic of suicide ideation and attempt in adolescents, there is a lack of theory-based, empirical research to shed light on these issues in this population and inform school counselors’ preventive and responsive practices. We utilized Joiner’s Interpersonal Theory of Suicide (IPTS) to examine the extent to which the interpersonal constructs of perceived burdensomeness and thwarted belongingness predicted adolescent suicide ideation and attempt by conducting two binomial logistic regressions on archival data from the 2017 eighth-grade Oregon Healthy Teens Survey. Six of the seven selected proxy items were statistically significant in each logistic model, with slight variance between the two. Our findings suggest that the interpersonal constructs of the IPTS are applicable to early adolescents and may be used to inform suicide prevention and intervention efforts among this population in school settings.


Mathematics ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 767
Author(s):  
Alexandra Băicoianu ◽  
Cristina Maria Păcurar ◽  
Marius Păun

The present paper concretizes the models proposed by S. Ri and N. Secelean. S. Ri proposed the construction of the fractal interpolation function(FIF) considering finite systems consisting of Rakotch contractions, but produced no concretization of the model. N. Secelean considered countable systems of Banach contractions to produce the fractal interpolation function. Based on the abovementioned results, in this paper, we propose two different algorithms to produce the fractal interpolation functions both in the affine and non-affine cases. The theoretical context we were working in suppose a countable set of starting points and a countable system of Rakotch contractions. Due to the computational restrictions, the algorithms constructed in the applications have the weakness that they use a finite set of starting points and a finite system of Rakotch contractions. In this respect, the attractor obtained is a two-step approximation. The large number of points used in the computations and the graphical results lead us to the conclusion that the attractor obtained is a good approximation of the fractal interpolation function in both cases, affine and non-affine FIFs. In this way, we also provide a concretization of the scheme presented by C.M. Păcurar .


2013 ◽  
Vol 31 (No. 6) ◽  
pp. 627-632 ◽  
Author(s):  
O.G. Nagel ◽  
M.P. Molina ◽  
R.L. Althaus

We proposed an experimental design of a microbial bioassay of dichotomous response (positive or negative) using Bacillus subtilis BGA for the detection of sulfonamide residues. In the first stage, the bioassay response time was reduced to 6 h by increasing the spore concentration of B. subtilis. Then, the effects of spore, indicator, trimethoprim (TMP) concentration, and volume of the culture medium were examined with a Plackett Burman design (2<sup>4-1</sup>). Finally, the effect of TMP concentration on the method detection capabilities and specificity was analysed using a logistic model with interaction. The detection capabilities of sulfonamides in milk are close to the MRLs when using 500 mg/l of TMP in the culture medium of the bioassay. It is concluded that the experimental design techniques and a logistic regression model can be used to design successfully a dichotomous response bioassay.


Fermentation ◽  
2021 ◽  
Vol 7 (2) ◽  
pp. 84
Author(s):  
Vidal Flores-Copa ◽  
Luis Romero-Soto ◽  
Danitza Romero-Calle ◽  
María Teresa Alvarez-Aliaga ◽  
Felipe Orozco-Gutierrez ◽  
...  

Candida maltosa was cultivated in the liquid phase of residual brewing yeast, a major brewery residue, to produce biomass and biofilm. Using response surface methodology, the effect of two variables at two different levels was investigated. The independent variables were agitation speed (at 100 and 200 rpm), and aeration (at 1 and 3 L min−1). Aeration was identified to be important for the production of both biomass and biofilm, while agitation was the only factor significantly affecting biofilm production. The maximal production of biofilm (2.33 g L−1) was achieved for agitation of 200 rpm and aeration of 1 L min−1, while the maximum for biomass (16.97 g L−1) was reached for 100 rpm agitation and 3 L min−1 air flow. A logistic model applied to predict the growth of C. maltosa in the exponential phase and the biofilm production, showed a high degree of agreement between the prediction and the actual biomass measured experimentally. The produced biofilms were further characterized using Fourier-transform infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Thermogravimetric Analysis (TGA). FTIR allowed the identification of methyl, carbonyl ester and sulfate groups, and revealed the presence of uronic acid moieties and glycosidic bonds. Water-retention ability up to relatively high temperatures was revealed by TGA, and that makes the produced biofilm suitable for production of hydrogels. SEM also gave indications on the hydrogel-forming potential of the biofilm.


Sign in / Sign up

Export Citation Format

Share Document