Determination of the most significant manufacturing process parameters using collected past data can be very helpful in solving important industrial problems, such as the detection of root causes of deteriorating product quality, the selection of the most efficient parameters to control the process, and the prediction of breakdowns of machines, equipment, etc. A methodology of determination of relative significances of process variables and possible interactions between them, based on interrogations of generalized regression models, is proposed and tested. The performance of several types of data mining tool, such as artificial neural networks, support vector machines, regression trees, classification trees, and a naïve Bayesian classifier, is compared. Also, some simple non-parametric statistical methods, based on an analysis of variance (ANOVA) and contingency tables, are evaluated for comparison purposes. The tests were performed using simulated data sets, with assumed hidden relationships, as well as on real data collected in the foundry industry. It was found that the performance of significance and interaction factors obtained from regression models, and, in particular, neural networks, is satisfactory, while the other methods appeared to be less accurate and/or less reliable.
Tourism pressure on protected areas with attractive landscapes leads to environmental modifications. Eutrophication poses the main threat to the quality of water in alpine lakes. Even small inflows of biogenic elements can disrupt the ecological balance of these ecosystems. The aim of this study was to verify the hypothesis that recreational activities and easy access to alpine lakes contribute to changes in their ecological status. This hypothesis was verified by analyzing the presence of hydromacrophytes in two lakes of the Tatra National Park (Poland). The analysis was carried out along segments of hiking trails which were evaluated for accessibility to the studied lakes. Underwater surveys were carried out during scuba diving expeditions in 2012–2016. Submerged vegetation was evaluated in both lakes. This is the first study in Poland and one of the few projects in the world to have relied on such extensive support from scuba divers to generate highly accurate measurements. The study demonstrated that lake bottoms were extensively covered by Potamogeton friesii in the vicinity of trail segments with easy access to lakes. Our results show that tourism pressure contributes to the growth of aquatic vegetation in some areas of alpine lakes. We relied on our findings to propose several modifications to the routes of the evaluated tourist trails to minimize the impact of anthropogenic pressure on the studied lakes.
Abstract. In 2000 and 2001, larval vendace, Coregonus albula (L.), were marked and released into Lake Wigry. The larvae were immersed in alizarin red S. Of the 19.2 million vendace larvae released in 2000, 2 million were marked (10.4% of the overall number of fish released), and in 2001 of the 18.8 million fish released, 7 million were marked (47.8%). In subsequent years, otoliths were excised from caught vendace and the number of them with alizarin marks was determined. It was assumed that all unmarked specimens came equally from natural spawning and stocking assuming that survival is equal in both forms of recruitment. It was confirmed that 82.4% of the vendace caught from the 2000 generation originated from stocking, while this figure was 64.2% of all specimens caught from the 2001 generation. Lake Wigry hosts the most abundant vendace population in Poland, and this stock spawns on a massive scale annually. Even so, the study described herein provides evidence of just how important systematic stocking is to the maintenance of the vendace population in this lake.
SUMMARY 1. A biomanipulation experiment was carried out in a small (10 ha), but relatively deep (17 m) and highly eutrophic lake in northern Poland. The lake had been stocked in 1996, 1997 and 1998 with a variety of piscivorous fish (pike, catfish, trout and pikeperch), in order to reduce numbers of cyprinid planktivores. 2. Piscivore stocking was associated with a threefold decrease in the offshore fish density (night echosounding). Despite this reduction, the large planktonic cladoceran, Daphnia hyalina, remained scarce, whereas the density of small‐sized zooplankton increased greatly. 3. The lack of demographic response in D. hyalina was probably due to the anoxia in the hypolimnetic refuge of this vertically migrating species. The anoxic hypolimnion, below 3–4 m depth, was inhabited day and night by numerous Chaoborus flavicans larvae. 4. Changes in zooplankton were associated with shifts in the taxonomic composition (from single‐cell green algae to filamentous cyanobacteria), size structure (from nano‐ to net phytoplankton) and seasonal dynamics of phytoplankton, but not in the average biomass of planktonic algae. A clear‐water phase, which was absent in the prestocking years, developed in spring, with Secchi depth reaching 2.5 m, a value which had never been recorded in the 20 years preceding the biomanipulation. In general, the lake's status was switched from hypertrophic to eutrophic. 5. Deteriorating food conditions, resulting from qualitative changes in the phytoplankton community, combined with predation pressure by the remaining fish and Chaoborus larvae were associated with the ultimate elimination of D. hyalina from the lake.
Abstract. The aim of the study was to determine the age and length growth rates of vendace, Coregonus albula (L.), from Lake Wigry (northeastern Poland). Fish were captured from 2001 to 2005 in the months of August and September. The most frequent age group in the catches was 2+, which comprised 53% of all fish caught. Growth was determined using Dahl-Lee and Rosa Lee back-calculation methods. These were the basis for calculating mathematical growth rate models. The growth that best corresponded with the empirical data was that calculated with a second-degree polynomial model based on Rosa Lee back-calculations. Fish aged 3+ were characterized by average length growth and attained a mean body length (SL) of 17.2 cm.
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