Costel Sârbu - Academia.edu (original) (raw)
Papers by Costel Sârbu
Journal of the Science of Food and Agriculture
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Intelligent Systems with Applications
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2019 IEEE 15th International Scientific Conference on Informatics
The proper selection of the similarity measure may be of paramount importance for the clustering ... more The proper selection of the similarity measure may be of paramount importance for the clustering result especially if the clusters overlap. Therefore, the aim of this paper is to study the influence of some widely known similarity measures on the clustering structure. The analysis uses a clustering algorithm based on rough sets which is able to discover hybrid data (outliers and instances that are close enough to more than one cluster). In this paper, we examine the similarity measures influence on the overlapping regions as well. Since the standard data sets do not offer specific information regarding the overlapping areas, we also propose an approach for extracting this data in order to be used for benchmarking purposes. Experiments conducted on standard data sets outline the importance of the proper similarity measure selection.
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International Conference on Advancements of Medicine and Health Care through Technology; 12th - 15th October 2016, Cluj-Napoca, Romania, 2017
Two classical chemometrics methods namely Cluster Analysis and Principal Component Analysis have ... more Two classical chemometrics methods namely Cluster Analysis and Principal Component Analysis have been applied to the evaluation of clinical data of several patients. A high correlation could be observed between some clinical parameters.
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The retention behaviour of some selected synthetic dyes have been investigated on RP-18F254S, RP-... more The retention behaviour of some selected synthetic dyes have been investigated on RP-18F254S, RP-18W/ UV254 and CNF254S plates using methanol–water mixture in different volume proportions as mobile phases. The RM values of the compounds decreased linearly with increasing concentration of methanol in the mobile phase in all cases. On the basis of the linear relationship between retention (RM) values and volume fraction of methanol, values of RM0 corresponding to 100% water were obtained by extrapolation using five isocratic RM values. The regression determination coefficients obtained for all stationary phases were excellent (higher than 0.99 in all cases). The good regularities of profiles of retention indices (RM and PC1/RM) indicated that the same mechanism (lipophilic interactions) is dominant in all cases and all types of stationary phases (RP-18, RP-18W and CN) appear to be suitable for estimating the lipophilicity of selected synthetic dyes. The chromatographic lipophilicity v...
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Journal of Environmental Science and Health, Part A, 2020
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Edible mushrooms have been recognized as highly nutritional food for a long time, due to their sp... more Edible mushrooms have been recognized as highly nutritional food for a long time, due to their specific flavor, texture and also for therapeutic effects. This study proposes a new simple approach, based on FT-IR analysis, followed by statistical methods, in order to differentiate three wild mushrooms species from Romanian spontaneous flora, namely Armillaria mellea, Boletus edulis and Cantharellus cibarius. The preliminary data treatment consisted of data set reduction with principal component analysis (PCA), which provided scores for the next methods. Linear discriminant analysis (LDA) manage to 100% classify the three species and the cross validation step of the method returned 97.4% of correctly classified samples. Only one A. mellea sample overlapped on B. edulis group. When kNN was used in the same manner as LDA, the overall percent of correctly classified samples from the training step was 86.21%, while for holdout set the percent raised at 94.74%. The lowered values obtained ...
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Journal of Endodontics, 2018
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Chemosphere, 2017
The study proposes a combined model based on diagrams (Gibbs, Piper, Stuyfzand Hydrogeochemical C... more The study proposes a combined model based on diagrams (Gibbs, Piper, Stuyfzand Hydrogeochemical Classification System) and unsupervised statistical approaches (Cluster Analysis, Principal Component Analysis, Fuzzy Principal Component Analysis, Fuzzy Hierarchical Cross-Clustering) to describe natural enrichment of inorganic arsenic and co-occurring species in groundwater in the Banat Plain, southwestern Romania. Speciation of inorganic As (arsenite, arsenate), ion concentrations (Na(+), K(+), Ca(2+), Mg(2+), HCO3(-), Cl(-), F(-), SO4(2-), PO4(3-), NO3(-)), pH, redox potential, conductivity and total dissolved substances were performed. Classical diagrams provided the hydrochemical characterization, while statistical approaches were helpful to establish (i) the mechanism of naturally occurring of As and F(-) species and the anthropogenic one for NO3(-), SO4(2-), PO4(3-) and K(+) and (ii) classification of groundwater based on content of arsenic species. The HCO3(-) type of local groun...
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Revista de Chimie -Bucharest- Original Edition-
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Computers & Geosciences, 2014
ABSTRACT The characteristics of pore water and slate samples are critically analyzed using fuzzy ... more ABSTRACT The characteristics of pore water and slate samples are critically analyzed using fuzzy hierarchical cross-clustering statistical techniques. The main aim of this study was to investigate the source of contamination near an abandoned uranium mine in Germany. The mining activities were abandoned in the 1990s, the site was closed, and the surrounding area was remediated. However, heavy metal contamination is still detectable in water, soil and plants today. Hence, investigating the source of the current contamination is an important task. In order to achieve the goal, results from chemical analysis of both pore water samples and leachates from slate samples were initially analyzed using hard (classical) hierarchical clustering algorithms that did not provide meaningful results. By using two fuzzy clustering algorithms, Fuzzy Divisive Hierarchical Clustering (FDHC) and Fuzzy Hierarchical Cross-Clustering (FHCC), a relationship between the leachate from Ordovician-Silurian slate samples (10 samples collected from the test site and the surrounding area) and pore water samples (53 samples collected from 3 locations within the test site at 3 depths over the course of 4 years) was identified. The leachate data formed a cluster which was statistically similar to the cluster formed by the pore water samples collected from two of three locations. In addition, the fuzzy cross-clustering approach allowed for the identification of the characteristics (qualitative and quantitative) responsible for the observed similarities between all the samples. We conclude that the fuzzy algorithms were a better tool for the analysis and interpretation of geological/hydrogeological data where the data sets have an inherent vagueness/uncertainty.
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Materials Chemistry and Physics, 1985
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Journal of Chromatography A, 1985
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Journal of the American Oil Chemists' Society, 2010
Silica gel plates impregnated with a variety of oils including vegetable oils (olive, sunflower a... more Silica gel plates impregnated with a variety of oils including vegetable oils (olive, sunflower and corn oil) and synthetic oils (trioctylamine and paraffin oil) were evaluated and compared with the commercially available reversed‐phases TLC plates (RP‐18, RP‐18W, and CN). A series of selected lipophilic vitamins was employed to evaluate the suitability of oils as reversed‐phases for TLC and to provide different lipophilicity indices: RM0, scores corresponding to the first principal component of RF and/or RM, the arithmetic mean of RF and RM values obtained with solvent mixture containing various concentrations of methanol in water. The retention results were excellent (r > 0.98) and allowed accurate estimation of lipophilicity of selected vitamins and to ranking the lipophilicity of oils when comparing with chemically bonded phases. Concerning the lipophilicity scale of vegetable oils, it is worth noting that corn oil presents the highest lipophilicity, closely followed by the o...
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Environmetrics, 1999
ABSTRACT
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ABSTRACT
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ABSTRACT
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ABSTRACT
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Journal of the Science of Food and Agriculture
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Intelligent Systems with Applications
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2019 IEEE 15th International Scientific Conference on Informatics
The proper selection of the similarity measure may be of paramount importance for the clustering ... more The proper selection of the similarity measure may be of paramount importance for the clustering result especially if the clusters overlap. Therefore, the aim of this paper is to study the influence of some widely known similarity measures on the clustering structure. The analysis uses a clustering algorithm based on rough sets which is able to discover hybrid data (outliers and instances that are close enough to more than one cluster). In this paper, we examine the similarity measures influence on the overlapping regions as well. Since the standard data sets do not offer specific information regarding the overlapping areas, we also propose an approach for extracting this data in order to be used for benchmarking purposes. Experiments conducted on standard data sets outline the importance of the proper similarity measure selection.
Bookmarks Related papers MentionsView impact
International Conference on Advancements of Medicine and Health Care through Technology; 12th - 15th October 2016, Cluj-Napoca, Romania, 2017
Two classical chemometrics methods namely Cluster Analysis and Principal Component Analysis have ... more Two classical chemometrics methods namely Cluster Analysis and Principal Component Analysis have been applied to the evaluation of clinical data of several patients. A high correlation could be observed between some clinical parameters.
Bookmarks Related papers MentionsView impact
The retention behaviour of some selected synthetic dyes have been investigated on RP-18F254S, RP-... more The retention behaviour of some selected synthetic dyes have been investigated on RP-18F254S, RP-18W/ UV254 and CNF254S plates using methanol–water mixture in different volume proportions as mobile phases. The RM values of the compounds decreased linearly with increasing concentration of methanol in the mobile phase in all cases. On the basis of the linear relationship between retention (RM) values and volume fraction of methanol, values of RM0 corresponding to 100% water were obtained by extrapolation using five isocratic RM values. The regression determination coefficients obtained for all stationary phases were excellent (higher than 0.99 in all cases). The good regularities of profiles of retention indices (RM and PC1/RM) indicated that the same mechanism (lipophilic interactions) is dominant in all cases and all types of stationary phases (RP-18, RP-18W and CN) appear to be suitable for estimating the lipophilicity of selected synthetic dyes. The chromatographic lipophilicity v...
Bookmarks Related papers MentionsView impact
Journal of Environmental Science and Health, Part A, 2020
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Edible mushrooms have been recognized as highly nutritional food for a long time, due to their sp... more Edible mushrooms have been recognized as highly nutritional food for a long time, due to their specific flavor, texture and also for therapeutic effects. This study proposes a new simple approach, based on FT-IR analysis, followed by statistical methods, in order to differentiate three wild mushrooms species from Romanian spontaneous flora, namely Armillaria mellea, Boletus edulis and Cantharellus cibarius. The preliminary data treatment consisted of data set reduction with principal component analysis (PCA), which provided scores for the next methods. Linear discriminant analysis (LDA) manage to 100% classify the three species and the cross validation step of the method returned 97.4% of correctly classified samples. Only one A. mellea sample overlapped on B. edulis group. When kNN was used in the same manner as LDA, the overall percent of correctly classified samples from the training step was 86.21%, while for holdout set the percent raised at 94.74%. The lowered values obtained ...
Bookmarks Related papers MentionsView impact
Journal of Endodontics, 2018
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Chemosphere, 2017
The study proposes a combined model based on diagrams (Gibbs, Piper, Stuyfzand Hydrogeochemical C... more The study proposes a combined model based on diagrams (Gibbs, Piper, Stuyfzand Hydrogeochemical Classification System) and unsupervised statistical approaches (Cluster Analysis, Principal Component Analysis, Fuzzy Principal Component Analysis, Fuzzy Hierarchical Cross-Clustering) to describe natural enrichment of inorganic arsenic and co-occurring species in groundwater in the Banat Plain, southwestern Romania. Speciation of inorganic As (arsenite, arsenate), ion concentrations (Na(+), K(+), Ca(2+), Mg(2+), HCO3(-), Cl(-), F(-), SO4(2-), PO4(3-), NO3(-)), pH, redox potential, conductivity and total dissolved substances were performed. Classical diagrams provided the hydrochemical characterization, while statistical approaches were helpful to establish (i) the mechanism of naturally occurring of As and F(-) species and the anthropogenic one for NO3(-), SO4(2-), PO4(3-) and K(+) and (ii) classification of groundwater based on content of arsenic species. The HCO3(-) type of local groun...
Bookmarks Related papers MentionsView impact
Revista de Chimie -Bucharest- Original Edition-
Bookmarks Related papers MentionsView impact
Computers & Geosciences, 2014
ABSTRACT The characteristics of pore water and slate samples are critically analyzed using fuzzy ... more ABSTRACT The characteristics of pore water and slate samples are critically analyzed using fuzzy hierarchical cross-clustering statistical techniques. The main aim of this study was to investigate the source of contamination near an abandoned uranium mine in Germany. The mining activities were abandoned in the 1990s, the site was closed, and the surrounding area was remediated. However, heavy metal contamination is still detectable in water, soil and plants today. Hence, investigating the source of the current contamination is an important task. In order to achieve the goal, results from chemical analysis of both pore water samples and leachates from slate samples were initially analyzed using hard (classical) hierarchical clustering algorithms that did not provide meaningful results. By using two fuzzy clustering algorithms, Fuzzy Divisive Hierarchical Clustering (FDHC) and Fuzzy Hierarchical Cross-Clustering (FHCC), a relationship between the leachate from Ordovician-Silurian slate samples (10 samples collected from the test site and the surrounding area) and pore water samples (53 samples collected from 3 locations within the test site at 3 depths over the course of 4 years) was identified. The leachate data formed a cluster which was statistically similar to the cluster formed by the pore water samples collected from two of three locations. In addition, the fuzzy cross-clustering approach allowed for the identification of the characteristics (qualitative and quantitative) responsible for the observed similarities between all the samples. We conclude that the fuzzy algorithms were a better tool for the analysis and interpretation of geological/hydrogeological data where the data sets have an inherent vagueness/uncertainty.
Bookmarks Related papers MentionsView impact
Materials Chemistry and Physics, 1985
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Journal of Chromatography A, 1985
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Journal of the American Oil Chemists' Society, 2010
Silica gel plates impregnated with a variety of oils including vegetable oils (olive, sunflower a... more Silica gel plates impregnated with a variety of oils including vegetable oils (olive, sunflower and corn oil) and synthetic oils (trioctylamine and paraffin oil) were evaluated and compared with the commercially available reversed‐phases TLC plates (RP‐18, RP‐18W, and CN). A series of selected lipophilic vitamins was employed to evaluate the suitability of oils as reversed‐phases for TLC and to provide different lipophilicity indices: RM0, scores corresponding to the first principal component of RF and/or RM, the arithmetic mean of RF and RM values obtained with solvent mixture containing various concentrations of methanol in water. The retention results were excellent (r > 0.98) and allowed accurate estimation of lipophilicity of selected vitamins and to ranking the lipophilicity of oils when comparing with chemically bonded phases. Concerning the lipophilicity scale of vegetable oils, it is worth noting that corn oil presents the highest lipophilicity, closely followed by the o...
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Environmetrics, 1999
ABSTRACT
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