This study examined early stages (3-5 years) of spontaneous primary vegetation succession on a model locality drastically altered by long term fluvial deposition of copper tailings in Eastern Serbia. In a large-scale survey, 115 samples of herbaceous vegetation (with a total of 75 species) were harvested from standardized 1m x 1m quadrates, and concomitant soil samples collected and their relevant physicochemical properties analysed. Primary succession depended on the establishment of five pioneer species (Rumex acetosella, Agrostis capillaris, Calamagrostis epigeios, Persicaria lapathifolia and Chenopodium botrys). Unconstrained ordination showed very clear vegetation gradients, significantly correlated with the key soil constraints (from Cu excess to low pH and nutrient deficiency), while the distribution of the five edificatory pioneers showed high degree of dependence on the micro-level habitat conditions. This work demonstrates that in such a complex setup with severe abiotic filtering, sufficient sampling effort can reveal strong patterns in a process commonly considered very stochastic.
{"title":"Highly patterned primary succession after fluvial deposition of mining waste","authors":"N. Nikolic","doi":"10.5937/univtho10-24743","DOIUrl":"https://doi.org/10.5937/univtho10-24743","url":null,"abstract":"This study examined early stages (3-5 years) of spontaneous primary vegetation succession on a model locality drastically altered by long term fluvial deposition of copper tailings in Eastern Serbia. In a large-scale survey, 115 samples of herbaceous vegetation (with a total of 75 species) were harvested from standardized 1m x 1m quadrates, and concomitant soil samples collected and their relevant physicochemical properties analysed. Primary succession depended on the establishment of five pioneer species (Rumex acetosella, Agrostis capillaris, Calamagrostis epigeios, Persicaria lapathifolia and Chenopodium botrys). Unconstrained ordination showed very clear vegetation gradients, significantly correlated with the key soil constraints (from Cu excess to low pH and nutrient deficiency), while the distribution of the five edificatory pioneers showed high degree of dependence on the micro-level habitat conditions. This work demonstrates that in such a complex setup with severe abiotic filtering, sufficient sampling effort can reveal strong patterns in a process commonly considered very stochastic.","PeriodicalId":22896,"journal":{"name":"The University Thought - Publication in Natural Sciences","volume":"9 1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76053769","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Stark full widths at half maximum (FWHM) for 26 6s-6p transitions in Tb III spectrum have been calculated for electron density of 1017 cm−3 within a temperature range of 5 000 K to 80 000 K, by using the simplified modified semiempirical (SMSE) method. The results obtained are used for the consideration of Strak width regularities within the investigated transition array.
利用简化的修正半经验(SMSE)方法，在5 000 K ~ 8 000 K的温度范围内，计算了Tbⅲ谱中电子密度为1017 cm−3的26个6s-6p跃迁的Stark全宽(FWHM)。所得结果用于考虑所研究的过渡阵列内条纹宽度的规律。
{"title":"Stark broadening of Tb III spectral lines originating from 6s-6p transitions","authors":"S. Dimitrijević","doi":"10.5937/univtho10-26397","DOIUrl":"https://doi.org/10.5937/univtho10-26397","url":null,"abstract":"Stark full widths at half maximum (FWHM) for 26 6s-6p transitions in Tb III spectrum have been calculated for electron density of 1017 cm−3 within a temperature range of 5 000 K to 80 000 K, by using the simplified modified semiempirical (SMSE) method. The results obtained are used for the consideration of Strak width regularities within the investigated transition array.","PeriodicalId":22896,"journal":{"name":"The University Thought - Publication in Natural Sciences","volume":"10 1","pages":"72-77"},"PeriodicalIF":0.0,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71152288","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
D. Gurešić, Sonja Ž. Đurić, Tina P. Andrejević, Mirjana Popsavin, Biljana Đ. Glišić
Polynuclear silver(I) complex, [Ag(NO3-O)(2,2’-bq-N,N’)]n, was synthesized by the reaction of equimolar amount of silver(I) nitrate and 2,2’-biquinoline (2,2’-bq) in ethanol at room temperature. The characterization of the complex was established on the basis of elemental microanalysis, IR, NMR (H and C) and UV-Vis spectroscopic techniques. The results of spectroscopic analyses revealed that in [Ag(NO3-O)(2,2’-bq-N,N’)]n complex, 2,2’-bq ligand behaves as a chelate, while the remaining coordination sites are occupied by the oxygen atoms of two nitrates.
{"title":"Synthesis and spectroscopic characterization of polynuclear silver(I) complex with 2,2'-biquinoline","authors":"D. Gurešić, Sonja Ž. Đurić, Tina P. Andrejević, Mirjana Popsavin, Biljana Đ. Glišić","doi":"10.5937/univtho10-25898","DOIUrl":"https://doi.org/10.5937/univtho10-25898","url":null,"abstract":"Polynuclear silver(I) complex, [Ag(NO3-O)(2,2’-bq-N,N’)]n, was synthesized by the reaction of equimolar amount of silver(I) nitrate and 2,2’-biquinoline (2,2’-bq) in ethanol at room temperature. The characterization of the complex was established on the basis of elemental microanalysis, IR, NMR (H and C) and UV-Vis spectroscopic techniques. The results of spectroscopic analyses revealed that in [Ag(NO3-O)(2,2’-bq-N,N’)]n complex, 2,2’-bq ligand behaves as a chelate, while the remaining coordination sites are occupied by the oxygen atoms of two nitrates.","PeriodicalId":22896,"journal":{"name":"The University Thought - Publication in Natural Sciences","volume":"33 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84311540","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Panic, Sergei Mohanchenko, C. Stefanovic, M. Stefanovic
This paper addresses the first-order outage statistics of asymmetrical radio frequency (RF)-optical wireless (OW) relay systems over non turbulent-induced-fading (nTIF) and turbulent-induced-fading (TIF) channels. We rely on dual-hop amplify-and-forward relay (AFR) scheme and provide detailed mathematical development for derivation of novel exact analytical as well as novel closed form approximative expressions for: i). cumulative distribution function, ii.) outage probability, and iii.) average bit-error-rate. The system under consideration is modeled as the product of independent Nakagmi-m and double squared Nakagami-m (also known as Gamma-Gamma) random processes. The obtained results of the proposed system are graphically presented for RF -OW TIF and nTIF channel sets of parameters. Moreover, the detailed comparisons of exact and approximated numerical results whose derivation resorts on exponential Laplace approximation method (LAM) are provided and thoroughly examined for the considered RF-OW statistical measures.
{"title":"First order outage statistics of asymmetrical RF-OW dual-hop relay communications","authors":"S. Panic, Sergei Mohanchenko, C. Stefanovic, M. Stefanovic","doi":"10.5937/univtho10-23091","DOIUrl":"https://doi.org/10.5937/univtho10-23091","url":null,"abstract":"This paper addresses the first-order outage statistics of asymmetrical radio frequency (RF)-optical wireless (OW) relay systems over non turbulent-induced-fading (nTIF) and turbulent-induced-fading (TIF) channels. We rely on dual-hop amplify-and-forward relay (AFR) scheme and provide detailed mathematical development for derivation of novel exact analytical as well as novel closed form approximative expressions for: i). cumulative distribution function, ii.) outage probability, and iii.) average bit-error-rate. The system under consideration is modeled as the product of independent Nakagmi-m and double squared Nakagami-m (also known as Gamma-Gamma) random processes. The obtained results of the proposed system are graphically presented for RF -OW TIF and nTIF channel sets of parameters. Moreover, the detailed comparisons of exact and approximated numerical results whose derivation resorts on exponential Laplace approximation method (LAM) are provided and thoroughly examined for the considered RF-OW statistical measures.","PeriodicalId":22896,"journal":{"name":"The University Thought - Publication in Natural Sciences","volume":"10 1","pages":"57-62"},"PeriodicalIF":0.0,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71152026","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The oscillation criteria of different types of differential equations are often the topic of numerous scientific papers, because their application in nuclear physics, fluid mechanics, relativistic mechanics, the study of chemical reactions in the system and in general are large in science. In this paper, the oscillation criteria using averaging functions of the half-linear differential equation are generalized to the half-linear differential equation with delay, under the appropriate assumptions for the delay function. Suitable examples illustrate the application of set oscillation criteria.
{"title":"Oscillation criteria for second order half-linear differential equations with delay","authors":"Radica Bojičić, T. Jovanović","doi":"10.5937/univtho9-22404","DOIUrl":"https://doi.org/10.5937/univtho9-22404","url":null,"abstract":"The oscillation criteria of different types of differential equations are often the topic of numerous scientific papers, because their application in nuclear physics, fluid mechanics, relativistic mechanics, the study of chemical reactions in the system and in general are large in science. In this paper, the oscillation criteria using averaging functions of the half-linear differential equation are generalized to the half-linear differential equation with delay, under the appropriate assumptions for the delay function. Suitable examples illustrate the application of set oscillation criteria.","PeriodicalId":22896,"journal":{"name":"The University Thought - Publication in Natural Sciences","volume":"40 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85151907","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Power flow equation for step-index glass optical fiber was solved using recently reported unconditionally-positive finite difference (UPFD) scheme. Solution obtained using UPFD scheme was compared with solution obtained using standard explicit finite difference (EFD) scheme. For accuracy testing both schemes were compared with analytical solution for steady state distribution of given fiber. The advantage of UPFD is reflected in stability of the scheme regardless of discretization step taken. Nevertheless EFD scheme has better concurrence with analytical solution than UPFD. This is due to the additional truncation-error terms in the approximations of the first and second derivatives with respect to θ.
{"title":"Unconditionally positive finite difference and standard explicit finite difference schemes for power flow equation","authors":"B. Drljača, S. Savović","doi":"10.5937/univtho9-23312","DOIUrl":"https://doi.org/10.5937/univtho9-23312","url":null,"abstract":"Power flow equation for step-index glass optical fiber was solved using recently reported unconditionally-positive finite difference (UPFD) scheme. Solution obtained using UPFD scheme was compared with solution obtained using standard explicit finite difference (EFD) scheme. For accuracy testing both schemes were compared with analytical solution for steady state distribution of given fiber. The advantage of UPFD is reflected in stability of the scheme regardless of discretization step taken. Nevertheless EFD scheme has better concurrence with analytical solution than UPFD. This is due to the additional truncation-error terms in the approximations of the first and second derivatives with respect to θ.","PeriodicalId":22896,"journal":{"name":"The University Thought - Publication in Natural Sciences","volume":"80 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84121196","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The basin of Sitnica river represents a good option for chartometric investigation. In modern hydrology, digital and GIS analyses play very important role today. In this research we were able to obtain the main properties of the river basin and river network with the help of digital line generalization. The results from the two kind of maps with two scales 1:25.000 and 1:50.000 showed differences in length of the main river Sitnica and its tributaries. These differences may be included into the analysis of the Sitnica river network. For the first time it was concluded that the Sitnica river has bi-polar dendritic parallel network. The 80% of right tributaries have angles between 2° and 5° degrees in direction of the Sitnica river. The left tributaries have angles between 1° and 2° degrees with the main water-course.
{"title":"Generalization and chartometric analysis of the Sitnica river network system","authors":"Bojana Jandžiković","doi":"10.5937/univtho9-24340","DOIUrl":"https://doi.org/10.5937/univtho9-24340","url":null,"abstract":"The basin of Sitnica river represents a good option for chartometric investigation. In modern hydrology, digital and GIS analyses play very important role today. In this research we were able to obtain the main properties of the river basin and river network with the help of digital line generalization. The results from the two kind of maps with two scales 1:25.000 and 1:50.000 showed differences in length of the main river Sitnica and its tributaries. These differences may be included into the analysis of the Sitnica river network. For the first time it was concluded that the Sitnica river has bi-polar dendritic parallel network. The 80% of right tributaries have angles between 2° and 5° degrees in direction of the Sitnica river. The left tributaries have angles between 1° and 2° degrees with the main water-course.","PeriodicalId":22896,"journal":{"name":"The University Thought - Publication in Natural Sciences","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84001439","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
V. Jovanović, I. Ristić, A. Miletić, S. Cakić, Jelena Tanasić, J. Budinski-Simendic
Due to the growing problem caused by waste plastics, academia and industry, invest great dials of efforts to solve this problem and enable the sustainability of polymeric materials. One way, which can successfully solve this problem, is certainly the synthesis of new polymeric materials based on renewable raw materials. Therefore, in this paper, synthesis of polyester based on ricinoleic acid (as well as the methyl ester of ricinoleic acid) is presented, in order to obtain the polyol of the desired molar masses. The polymerization of the ricinoleic acid was performed in the presence of diethylene glycol, as an initiator, and titanium isopropoxide, as a catalyst. By analyzing the molar masses of the obtained polyesters, it has been confirmed that the control of the molecular weight of the polyricinoleic acid can be successfully accomplished by the addition of a precisely determined amount of diethylene glycol, thus enabling in this way the synthesis of polyols of desired properties. The molecular structure of the synthesized polyols is confirmed by FTIR and NMR spectroscopy. The analysis of the thermal properties showed that the glass transition temperatures of the synthesized polyols range from -70 to -80oC, which makes it possible to apply these materials in low-temperature applications. The slight increasment of thermal stability is observed, only with the increasment of molecular weight, which was confirmed by TG analysis. The viscosity measurement results confirmed that as the molar weight of synthesized polyester increases, the viscosity of the samples also increases.
{"title":"Synthesis of biodegradable polyester based on renewable resources","authors":"V. Jovanović, I. Ristić, A. Miletić, S. Cakić, Jelena Tanasić, J. Budinski-Simendic","doi":"10.5937/UNIVTHO9-18120","DOIUrl":"https://doi.org/10.5937/UNIVTHO9-18120","url":null,"abstract":"Due to the growing problem caused by waste plastics, academia and industry, invest great dials of efforts to solve this problem and enable the sustainability of polymeric materials. One way, which can successfully solve this problem, is certainly the synthesis of new polymeric materials based on renewable raw materials. Therefore, in this paper, synthesis of polyester based on ricinoleic acid (as well as the methyl ester of ricinoleic acid) is presented, in order to obtain the polyol of the desired molar masses. The polymerization of the ricinoleic acid was performed in the presence of diethylene glycol, as an initiator, and titanium isopropoxide, as a catalyst. By analyzing the molar masses of the obtained polyesters, it has been confirmed that the control of the molecular weight of the polyricinoleic acid can be successfully accomplished by the addition of a precisely determined amount of diethylene glycol, thus enabling in this way the synthesis of polyols of desired properties. The molecular structure of the synthesized polyols is confirmed by FTIR and NMR spectroscopy. The analysis of the thermal properties showed that the glass transition temperatures of the synthesized polyols range from -70 to -80oC, which makes it possible to apply these materials in low-temperature applications. The slight increasment of thermal stability is observed, only with the increasment of molecular weight, which was confirmed by TG analysis. The viscosity measurement results confirmed that as the molar weight of synthesized polyester increases, the viscosity of the samples also increases.","PeriodicalId":22896,"journal":{"name":"The University Thought - Publication in Natural Sciences","volume":"10 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83827259","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Milena J. Petrović, Milica Ivanović, Marijana Ðorðević
We analyze a performance profile of several accelerated and hybrid accelerated methods. All comparative methods are at least linearly convergent and have satisfied numerical characteristics regarding tested metrics: number of iterations, CPU time and number of function evaluations. Among the chosen set of methods we numerically show which one is the most efficient and the most effective. Therewith, we derived a conclusion about what type of method is more preferable to use considering analyzed metrics.
{"title":"Comparative performance analysis of some accelerated and hybrid accelerated gradient models","authors":"Milena J. Petrović, Milica Ivanović, Marijana Ðorðević","doi":"10.5937/UNIVTHO9-18174","DOIUrl":"https://doi.org/10.5937/UNIVTHO9-18174","url":null,"abstract":"We analyze a performance profile of several accelerated and hybrid accelerated methods. All comparative methods are at least linearly convergent and have satisfied numerical characteristics regarding tested metrics: number of iterations, CPU time and number of function evaluations. Among the chosen set of methods we numerically show which one is the most efficient and the most effective. Therewith, we derived a conclusion about what type of method is more preferable to use considering analyzed metrics.","PeriodicalId":22896,"journal":{"name":"The University Thought - Publication in Natural Sciences","volume":"39 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88469481","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"A critical review of the current checklist of butterflies of Serbia","authors":"P. Jakšić","doi":"10.5937/UNIVTHO9-19910","DOIUrl":"https://doi.org/10.5937/UNIVTHO9-19910","url":null,"abstract":"","PeriodicalId":22896,"journal":{"name":"The University Thought - Publication in Natural Sciences","volume":"13 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75442807","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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