Browsing by Subject "cluster analysis"

Sort by: Order: Results:

Now showing items 1-11 of 11
  • Atashi, Nahid; Tuure, Juuso; Alakukku, Laura; Rahimi, Dariush; Pellikka, Petri; Zaidan, Martha Arbayani; Vuollekoski, Henri; Rasanen, Matti; Kulmala, Markku; Vesala, Timo; Hussein, Tareq (2021)
    Model evaluation against experimental data is an important step towards accurate model predictions and simulations. Here, we evaluated an energy-balance model to predict dew formation occurrence and estimate its amount for East-African arid-climate conditions against 13 months of experimental dew harvesting data in Maktau, Kenya. The model was capable of predicting the dew formation occurrence effectively. However, it overestimated the harvestable dew amount by about a ratio of 1.7. As such, a factor of 0.6 was applied for a long-term period (1979-2018) to investigate the spatial and temporal variation of the dew formation in Kenya. The annual average of dew occurrence in Kenya was similar to 130 days with dew yield > 0.1 L/m(2)/day. The dew formation showed a seasonal cycle with the maximum yield in winter and minimum in summer. Three major dew formation zones were identified after cluster analysis: arid and semi-arid regions; mountain regions; and coastal regions. The average daily and yearly maximum dew yield were 0.05 and 18; 0.9 and 25; and 0.15 and 40 L/m(2)/day; respectively. A precise prediction of dew occurrence and dew yield is very challenging due to inherent limitations in numerical models and meteorological input parameters.
  • Hebestreit, Antje; Intemann, Timm; Siani, Alfonso; De Henauw, Stefaan; Eiben, Gabriele; Kourides, Yiannis A.; Kovacs, Eva; Moreno, Luis A.; Veidebaum, Toomas; Krogh, Vittorio; Pala, Valeria; Bogl, Leonie H.; Hunsberger, Monica; Boernhorst, Claudia; Pigeot, Iris; I Family Consortium (2017)
    The aim of this study was to determine whether an association exists between children's and parental dietary patterns (DP), and whether the number of shared meals or soft drink availability during meals strengthens this association. In 2013/2014 the I. Family study cross-sectionally assessed the dietary intakes of families from eight European countries using 24-h dietary recalls. Usual energy and food intakes from six-to 16-year-old children and their parents were estimated based on the NCI Method. A total of 1662 child-mother and 789 child-father dyads were included; DP were derived using cluster analysis. We investigated the association between children's and parental DP and whether the number of shared meals or soft drink availability moderated this association using mixed effects logistic regression models. Three DP comparable in children and parents were obtained: Sweet & Fat, Refined Cereals, and Animal Products. Children were more likely to be allocated to the Sweet & Fat DP when their fathers were allocated to the Sweet & Fat DP and when they shared at least one meal per day (OR 3.18; 95% CI 1.84; 5.47). Being allocated to the Sweet & Fat DP increased when the mother or the father was allocated to the Sweet & Fat DP and when soft drinks were available (OR 2.78; 95% CI 1.80; 4.28 or OR 4.26; 95% CI 2.16; 8.41, respectively). Availability of soft drinks and negative parental role modeling are important predictors of children's dietary patterns.
  • Arar, Sharif; Al-Hunaiti, Afnan; Masad, Mohanad H.; Maragkidou, Androniki; Wraith, Darren; Hussein, Tareq (2019)
    In this study, we performed elemental analysis for floor dust samples collected in Jordanian microenvironments (dwellings and educational building). We performed intercorrelation and cluster analysis between the elemental, polyaromatic hydrocarbon (PAH), and microorganism concentrations. In general, the educational building workshops had the highest elemental contamination. The age of the dwelling and its occupancy played a role on the elemental contamination level: older and more occupied dwellings had greater contamination. The elemental contamination at a dwelling entrance was observed to be higher than in the living room. We found exceptionally high concentrations for Fe and Mn in the educational workshop and additionally, Hg, Cr, and Pb concentrations exceeded the limits set by the Canadian Council of Ministers of the Environment. According to the cluster analysis, we found three major groups based on location and contamination. According to the enrichment factor (EF) assessment, Al, Co, Mn, Ti, and Ba had EF <2 (i.e., minimal enrichment) whereas P, S, Pb, Sb, Mo, Zn, Hg, and Cu had EF > 40 (i.e., extremely enriched). In contrast, Ca and P were geogenically enriched. Furthermore, significant Spearman correlations indicated nine subgroups of elemental contamination combined with PAHs and microbes.
  • Kyrö, Minna (Helsingfors universitet, 2011)
    FTIR spectroscopy (Fourier transform infrared spectroscopy) is a fast method of analysis. The use of interferometers in Fourier devices enables the scanning of the whole infrared frequency region in a couple of seconds. There is no need to elaborate sample preparation when the FTIR spectrometer is equipped with an ATR accessory and the method is therefore easy to use. ATR accessory facilitates the analysis of various sample types. It is possible to measure infrared spectra from samples which are not suitable for traditional sample preparation methods. The data from FTIR spectroscopy is frequently combined with statistical multivariate analysis techniques. In cluster analysis the data from spectra can be grouped based on similarity. In hierarchical cluster analysis the similarity between objects is determined by calculating the distance between them. Principal component analysis reduces the dimensionality of the data and establishes new uncorrelated principal components. These principal components should preserve most of the variation of the original data. The possible applications of FTIR spectroscopy combined with multivariate analysis have been studied a lot. For example in food industry its feasibility in quality control has been evaluated. The method has also been used for the identification of chemical compositions of essential oils and for the detection of chemotypes in oil plants. In this study the use of the method was evaluated in the classification of hog's fennel extracts. FTIR spectra of extracts from different plant parts of hog's fennel were compared with the measured FTIR spectra of standard substances. The typical absorption bands in the FTIR spectra of standard substances were identified. The wave number regions of the intensive absorption bands in the spectra of furanocoumarins were selected for multivariate analyses. Multivariate analyses were also performed in the fingerprint region of IR spectra, including the wave number region 1785-725 cm-1. The aim was to classify extracts according to the habitat and coumarin concentration of the plants. Grouping according to habitat was detected, which could mainly be explained by coumarin concentrations as indicated by analyses of the wave number regions of the selected absorption bands. In these analyses extracts mainly grouped and differed by their total coumarin concentrations. In analyses of the wave number region 1785-725 cm-1 grouping according to habitat was also detected but this could not be explained by coumarin concentrations. These groupings may have been caused by similar concentrations of other compounds in the samples. Analyses using other wave number regions were also performed, but the results from these experiments did not differ from previous results. Multivariate analyses of second-order derivative spectra in the fingerprint region did not reveal any noticeable changes either. In future studies the method could perhaps be further developed by investigating narrower carefully selected wave number regions of second-order derivative spectra.
  • Nurttila, Suvi (Helsingfors universitet, 2014)
    In today's society it is desirable to be successful and continuously progressive. At the same time it is seen important to focus on one's well-being and seeking optimal experiences. In studying, the interaction between motivation and well-being as well as the importance of positive learning experiences is an actual entirety. Taking students conceptions of learning and knowledge into account brings in a richer perspective that has been less frequently studied. Conceptions of learning and knowledge, otherwise epistemologies, are crucial in governing student's ways of interpreting and evaluating information, as well as their view on the learning process. An important recent insight on the field of educational research is the growing idea that motivational, emotional and cognitive dimensions are not only intrinsically significant, but also in intense interaction with each other and with the learning environment. The aim of this study was to investigate what kinds of motivational factors and problems in well-being do novice students experience in their studies, and also what their epistemologies are like. The approach was person-oriented. Motivational factors were: experienced challenge and competence, thinking strategies and attributions, and study engagement. Problems in well-being were measured through emotional dimension (stress, exhaustion) on the one hand, and through motivational dimension (lack of interest, task avoidance) on the other. Epistemologies measured in this study were: collaborative knowledge building, reflective learning, metacognition, certainty of knowledge and practical value. The data (n=785) were collected in spring and autumn 2012 by using a questionnaire developed by RYM Indoor Environment project. The participants were first and second year students from Aalto university of Technology and four departments in University of Helsinki: Department of Teacher education, Department of Chemistry, Faculty of Theology, and Faculty of Law. K-means cluster analysis was used for clustering students into homogenous groups that presented their experienced motivational factors. To see whether the groups differed in terms of problems in well-being or epistemologies, Oneway analysis of variance was conducted. Also potential differences in certain background variables were investigated by using crosstabs (gender, study discipline) and Kruskal-Wallis test (age). Three studying profiles were identified: 1) pessimistic, 2) bored, 3) engaged. Pessimistic students reported the lowest study engagement, optimism and competence and the highest task avoidance and problems in well-being. They valued certain knowledge the most. Bored students experienced the lowest challenge, quite low study engagement and moderate optimism, competence and lack of interest. They reported the lowest practical value of knowledge. Engaged students had the highest study engagement, optimism and competence, lowest task avoidance and the least problems in well-being. They valued collaborative knowledge building, reflective learning and metacognition the most. There were not found gender differences between the studying profiles. Instead, it turned out that pessimistic students were the youngest. When comparing different study disciplines, the results indicated that in the Department of Teacher education, as well as in the Faculties of Law and Theology, the largest section of participants was identified as engaged students. Among participants from Aalto university and the Department of Chemistry, the largest section was identified as pessimistic students. This study demonstrates the idea of the dynamic interplay between motivational, emotional and cognitive dimensions in studying. In conclusion, students personal motivational factors, well-being and epistemologies form unique entireties. It can be deduced on the basis of earlier research, that these entireties are of utmost importance regarding studying and can be either worthwhile or detrimental to it. In the future, more proof is needed about the concrete relations and potential effects on study success, for example, as supporting successful studying and graduating on schedule are topical politico-educational subjects in Finland. Also little is known about the relations between well-being and epistemologies. The results of this study could be utilized in developing and designing higher education.
  • Ketonen, Elina (Helsingfors universitet, 2011)
    Previous studies indicate that positive learning experiences are related to academic achievement as well as to well-being. On the other hand, emotional and motivational problems in studying may pose a risk for both academic achievement and well-being. Thus, emotions and motivation have an increasing role in explaining university students learning and studying. The relations between emotions, motivation, study success and well-being have been less frequently studied. The aim of this study was to investigate what kind of academic emotions, motivational factors and problems in studying students experienced five days before an exam of an activating lecture course, and the relations among these factors as well as their relation to self-study time and study success. Furthermore, the effect of all these factors on well-being, flow experience and academic achievement was examined. The term academic emotion was defined as emotion experienced in academic settings and related to studying. In the present study the theoretical background to motivational factors was based on thinking strategies and attributions, flow experience and task value. Problems in studying were measured in terms of exhaustion, anxiety, stress, lack of interest, lack of self-regulation and procrastination. The data were collected in December 2009 in an activating educational psychology lecture course by using a questionnaire. The participants (n=107) were class and kindergarten teacher students from the University of Helsinki. Most of them were first year students. The course grades were also gathered. Correlations and stepwise regression analysis were carried out to find out the factors that were related to or explained study success. The clusters that presented students' problems in studying as well as thinking strategies and attributions, were found through hierarchical cluster analysis. K-means cluster analysis was used to form the final groups. One-way analysis of variance, Kruskal-Wallis test and crosstabs were conducted to see whether the students in different clusters varied in terms of study success, academic emotions, task value, flow, and background variables. The results indicated that academic emotions measured five days before the exam explained about 30 % of the variance of the course grade; exhaustion and interest positively, and anxiety negatively. In addition, interest as well as the self-study time best explained study success on the course. The participants were classified into three clusters according to their problems in studying as well as their thinking strategies and attributions: 1) ill-being, 2) carefree, and 3) committed and optimistic students. Ill-being students reported most negative emotions, achieved the worst grades, experienced anxiety rather than flow and were also the youngest. Carefree students, on the other hand, expressed the least negative emotions and spent the least time on self-studying, and like committed students, experienced flow. In addition, committed students reported positive emotions the most often and achieved the best grades on the course. In the future, more in-depth understanding how and why especially young first year students experience their studying hard is needed, because early state of the studies is shown to predict later study success.
  • Lotsari, Eliisa; Dietze, Michael; Kämäri, Maria; Alho, Petteri; Kasvi, Elina (MDPI, 2020)
    Water 12 7 (2020)
    Macro-turbulent flows (i.e., coherent flow structures reaching through the whole water column), have not been studied widely in northern seasonally frozen rivers during both open-channel and ice-covered flow conditions. Thus, we aim: (1) to detect and compare the macro-turbulent flow, both at open-channel and ice-covered flow conditions; (2) to explore spatial variation of macro-turbulent flow characteristics within a meander bend; and (3) to detect the effects of near-bed layer velocity fluctuation on bedload transport during differing overall flow conditions. The analyses are based on 5–10 min-long acoustic Doppler current profiler (ADCP) measurements from a subarctic river. The ice-covered low flow, and open-channel higher and lower flow conditions were measured over the period of 2016 to 2020. This study found that macro-turbulent flow existed at all measurement locations under both open-channel and ice-covered flow conditions. Macro-turbulent flow was most consistent and obvious in the streamwise velocity component, and in particular at the inlet and outlet of the investigated meander bend. During all seasons, the near-bed velocities consistently exceeded the sufficient amount for sediment transport. At inlet and outlet areas, the greatest near-bed velocity fluctuation across the critical threshold for sediment transport coincided with the measurement times having frequent macro-turbulent flow.
  • Baranova, T; Kalendar, Ruslan; Kalayev, N; Sorokopudov, V; Burmenko, J (2018)
    Currently, woody plants attract special attention given the prospects of their involving in bio- and genomic technologies to address challenges of sustainable environment, biodiversity, food security and production of raw materials. Thence, studies of cytogenetic characteristics of woody plants are increasingly relevant. The change in a number of cytogenetic characteristics, in particular, mitotic activity, which may increase and decrease depending on the intensity of stress loads, an increase in the pathology of mitosis, etc., has been shown. However, attempts to identify the similarities and differences in cytogenetic characteristics in woody plants on the basis of the results of molecular genetic comparison weren’t conducted yet. Sequences of the internal transcribed spacer (ITS) regions of nuclear ribosomal NA were used to generate a phylogenetic hypothesis for disjuncting of wood species of the genus Aralia (J. Wen, 2000), to specify of Rhododendron systematic state (T.V. Baranova et al., 2014) and other genera of the family Ericaceae (O. Schwery et al., 2015). Cluster analysis of nucleotide sequences and construction of the dendrogram were carried out using the ML (Maximum Likelihood, Nearest-Neighbor-Interchange) method in the MEGA software. Germination of Rhododendron seeds was carried out in Petri dishes at room temperature. Roots were stained with acetohematoxylin, rinsed with distilled water, and suppressed micro-preparations were prepared using Goyer’s fluid. Nucleotide sequences of the ITS1-ITS2 spacer of the parent plants and cytogenetic parameters (mitotic activity, level and spectrum of pathological mitoses, number of cells with residual nucleoli in the metaphase-telophase mitosis stage) we obtained from seed progeny in four Rhododendron species introduced into the conditions of the Central Black Earth region of Russia. The identity of the nucleotide sequence of the spacer ITS1-ITS2 in species of the genus Rhododendron leads to their greater similarity in the aggregate of cytogenetic indices. However, there is no complete analogy of cytogenetic characteristics in the species studied that have the identical sequence ITS1-ITS2. On the basis of this comparison, it can be assumed that genetic similarity in the studied Rhododendron species causes the similarity of cytogenetic indices. According to mitotic activity in the root meristem of the seedlings, two groups can be distinguished among the seed progeny, i.e. with a high value of mitotic activity, namely Rhododendron dauricum (7.6±0.3 %) and Rh. mucronulatum (7.7±0.7 %), and with low value, namely Rh. sichotense (5.6±0.7 %) and Rh. ledebourii (6.1±0.6%). The greatest cytogenetic instability is noted in Rh. ledebourii (5.2±1.1 %, the level of pathologies of mitosis in this species is maximal), in three other species it was lower (from 3.5±0.5 % for Rh. sichotense to 1.6±0.4 % for Rh. dauricum mitosis pathologies). A higher level of cells with a residual nucleolus at the stage of metaphase—telophase mitosis indicates a greater intensity of synthetic processes associated with adaptation in conditions of introduction. For this indicator, we can distinguish two groups: i) Rh. sichotense (13.3±1.2 %) with a high level of cells with a residual nucleolus at the stage of metaphase—telophase of mitosis, and ii) Rh. mucronulatum (9.1±1.1 %), Rh. dauricum (10.2±1.0 %) and Rh. ledebourii (10.9±1.3 %) with low values. Despite the difference in cytogenetic parameters in the seed offspring of the studied species, a cluster analysis of the totality of the characteristics of the course of mitosis and nucleolar activity made it possible to distinguish two groups: 1) Rh. mucronulatum and Rh. dauricum; 2) Rh. ledebourii and Rh. sichotense.The cytogenetic characteristics of the seed offspring of the species studied are species-specific.
  • Niilekselä, Pia (Helsingin yliopisto, 2017)
    Entrance to academic studies does not automatically lead to commitment in one's studies. There may be differences in student commitment across different learning environments. In the present study, combinations of problems in studying medical students experience were investigated in a lecture-based learning environment (n = 246) and in a problem-based learning environment (n = 231). Also differences between the combinations in task avoidance and differences between the combinations in academic achievement were investigated in each learning environment. Medical students were classified in different learning environments by K-means cluster analysis by cases into groups based on the following variables: exhaustion, lack of self-regulation, lack of interest and distress. Three groups of commitment among medical students were identified in the lecture-based learning environment: committed, carefree and dysfunctional students. The profiles were related to task avoidance but not to study success. The committed students expressed less task avoidance than the carefree students and the dysfunctional students. The latter two groups of medical students did not differ from each other in this case. Also three groups of commitment among medical students were identified in the problem-based learning environment: committed, committed carefree and dysfunctional students. The profiles were related to task avoidance and study success. The dysfunctional students expressed more task avoidance than the committed carefree students and the committed students. The latter two groups of medical students did not differ from each other in this case. The committed students and the committed carefree students gained better grades than the dysfunctional students. However, the former two groups of medical students did not differ from each other in this case. The implications of the study for research are discussed.
  • Thomas, H. J. D.; Myers-Smith, I. H.; Bjorkman, A. D.; Elmendorf, S. C.; Blok, D.; Cornelissen, J. H. C.; Forbes, B. C.; Hollister, R. D.; Normand, S.; Prevey, J. S.; Rixen, C.; Schaepman-Strub, G.; Wilmking, M.; Wipf, S.; Cornwell, W. K.; Kattge, J.; Goetz, S. J.; Guay, K. C.; Alatalo, J. M.; Anadon-Rosell, A.; Angers-Blondin, S.; Berner, L. T.; Bjork, R. G.; Buchwal, A.; Buras, A.; Carbognani, M.; Christie, K.; Collier, L. Siegwart; Cooper, E. J.; Eskelinen, A.; Frei, E. R.; Grau, O.; Grogan, P.; Hallinger, M.; Heijmans, M. M. P. D.; Hermanutz, L.; Hudson, J. M. G.; Huelber, K.; Iturrate-Garcia, M.; Iversen, C. M.; Jaroszynska, F.; Johnstone, J. F.; Kaarlejärvi, E.; Kulonen, A.; Lamarque, L. J.; Levesque, E.; Little, C. J.; Michelsen, A.; Milbau, A.; Nabe-Nielsen, J.; Nielsen, S. S.; Ninot, J. M.; Oberbauer, S. F.; Olofsson, J.; Onipchenko, V. G.; Petraglia, A.; Rumpf, S. B.; Semenchuk, P. R.; Soudzilovskaia, N. A.; Spasojevic, M. J.; Speed, J. D. M.; Tape, K. D.; te Beest, M.; Tomaselli, M.; Trant, A.; Treier, U. A.; Venn, S.; Vowles, T.; Weijers, S.; Zamin, T.; Atkin, O. K.; Bahn, M.; Blonder, B.; Campetella, G.; Cerabolini, B. E. L.; Chapin, F. S.; Dainese, M.; de Vries, F. T.; Diaz, S.; Green, W.; Jackson, R. B.; Manning, P.; Niinemets, U.; Ozinga, W. A.; Penuelas, J.; Reich, P. B.; Schamp, B.; Sheremetev, S.; van Bodegom, P. M. (2019)
    Aim Plant functional groups are widely used in community ecology and earth system modelling to describe trait variation within and across plant communities. However, this approach rests on the assumption that functional groups explain a large proportion of trait variation among species. We test whether four commonly used plant functional groups represent variation in six ecologically important plant traits. Location Tundra biome. Time period Data collected between 1964 and 2016. Major taxa studied 295 tundra vascular plant species. Methods We compiled a database of six plant traits (plant height, leaf area, specific leaf area, leaf dry matter content, leaf nitrogen, seed mass) for tundra species. We examined the variation in species-level trait expression explained by four traditional functional groups (evergreen shrubs, deciduous shrubs, graminoids, forbs), and whether variation explained was dependent upon the traits included in analysis. We further compared the explanatory power and species composition of functional groups to alternative classifications generated using post hoc clustering of species-level traits. Results Traditional functional groups explained significant differences in trait expression, particularly amongst traits associated with resource economics, which were consistent across sites and at the biome scale. However, functional groups explained 19% of overall trait variation and poorly represented differences in traits associated with plant size. Post hoc classification of species did not correspond well with traditional functional groups, and explained twice as much variation in species-level trait expression. Main conclusions Traditional functional groups only coarsely represent variation in well-measured traits within tundra plant communities, and better explain resource economic traits than size-related traits. We recommend caution when using functional group approaches to predict tundra vegetation change, or ecosystem functions relating to plant size, such as albedo or carbon storage. We argue that alternative classifications or direct use of specific plant traits could provide new insights for ecological prediction and modelling.
  • Mukala, Elina (Helsingin yliopisto, 2015)
    In Finland, the vast majority of students complete their university degree later than the target times propose. This has been acknowledged to be problematic on a societal level. In previous studies, students' self-regulatory skills have risen as a main factor when the impeding and enhancing factors of studying have been explored. In addition to self-regulatory skills, students' academic emotions have been found to influence study performance. According to earlier studies, it is also relevant how students deal with their emotions. Psychologically flexible students are able to embrace their emotions and they are capable of living their lives according to their values. The aim of this study is to explore the self-regulatory skills, academic emotions and psychological flexibility of students in the Faculty of Humanities in University of Helsinki and the relationships between these concepts. In addition, a point of interest is how these factors are linked to study performance. The research data was collected by a survey. In addition the information of students' average scores and the amount of student credits were collected from the study register. 258 students responded to the questionnaire. Dimensions of self-regulation, academic emotions and psychological flexibility were explored by factor analysis and the links between these dimensions were examined by correlation analysis. In addition students were grouped based on their self-regulatory skills, psychological flexibility and experienced emotions by using two-step cluster analysis. The differences of the groups' study pace and means of grades were examined using one-way analysis of variance. Students felt that they are psychologically quite flexible, and they experienced more positive emotions than negative emotions. They also had rather good self-regulation skills. Psychological flexibility was associated with a feeling of hopefulness, and emotions were found to correlate with each other. However, there was no correlation between psychological flexibility and the regulation of learning. On the basis of cluster analysis, the students were classified into three groups: 1) hopeful, self-regulating and psychologically flexible students 2) students who have a contradictory attitude towards studying and have challenges in the regulation learning, and 3) students who experience feelings of anxiety and shame. There was no difference between the groups in the number of credits and the averages of grades. In the future, more information is needed about why some students experience a lot of negative emotions related to learning, and how important psychological flexibility is to the well-being of students and to study performance.