Cluster Compactness Research Articles

Using geometric and non‐geometric internal evaluators to compare eight vegetation classification methods

AbstractQuestions: How similar are solutions of eight commonly used vegetation classification methods? Which classification methods are most effective according to classification validity evaluators? How do evaluators with different optimality criteria differ in their assessments of classification efficacy? In particular, do evaluators which use geometric criteria (e.g. cluster compactness) and non‐geometric evaluators (which rely on diagnostic species) offer similar classification evaluations?Methods: We analysed classifications of two vegetation data‐sets produced by eight classification methods. Classification solutions were assessed with five geometric and four non‐geometric internal evaluators. We formally introduce three new evaluators: PARTANA, an intuitive variation on evaluators which use the ratio of within/between cluster dissimilarity as the optimality criterion, an adaptation of Morisita's index of niche overlap, and ISAMIC, an algorithm which measures the degree to which species are either always present or always absent within clusters.Results and Conclusions: 1. With the exception of single linkage hierarchical clustering, classifications resulting from the eight methods were often similar. 2. Although evaluators varied in their assessment of best overall classification method, they generally favored three hierarchical agglomerative clustering strategies: flexible beta (β=– 0.25), average linkage, and Ward's linkage. 3. Among introduced evaluators PARTANA appears to be an effective geometric strategy which provides assessments similar to C‐index and Gamma evaluators. Non‐geometric evaluators ISAMIC and Morisita's index demonstrate a strong bias for single linkage solutions. 4. Because non‐geometric criteria are of interest to phytosociologists there is a strong need for their continued development for use with vegetation classifications.

A density-based cluster validity approach using multi-representatives

Although the goal of clustering is intuitively compelling and its notion arises in many fields, it is difficult to define a unified approach to address the clustering problem and thus diverse clustering algorithms abound in the research community. These algorithms, under different clustering assumptions, often lead to qualitatively different results. As a consequence the results of clustering algorithms (i.e., data set partitionings) need to be evaluated as regards their validity based on widely accepted criteria. In this paper a cluster validity index, CDbw, is proposed which assesses the compactness and separation of clusters defined by a clustering algorithm. The cluster validity index, given a data set and a set of clustering algorithms, enables (i) the selection of the input parameter values that lead an algorithm to the best possible partitioning of the data set, and (ii) the selection of the algorithm that provides the best partitioning of the data set. CDbw handles efficiently arbitrarily shaped clusters by representing each cluster with a number of points rather than by a single representative point. A full implementation and experimental results confirm the reliability of the validity index showing also that its performance compares favourably to that of several others.

Magnetic clusters and fold energies

We are concerned with variational properties of a fold energy for a unit, dilation-invariant gradient field (called a cluster) in the unit disk. We show that boundedness of a fold energy implies $L^{1}$-compactness of clusters. We also show that a fold energy is $L^{1}$-lower semicontinuous. We characterize absolute minimizers. We also give a sequence of stationary states and discuss its stability. Surprisingly, the stability depends upon $q$, the power of modulus of the jump discontinuities, in the definition of the fold energy.

Effects of Early Defoliation on Shoot Photosynthesis, Yield Components, and Grape Composition

The effectiveness of early leaf removal on high-yielding cultivars Sangiovese and Trebbiano (<i>Vitis vinifera</i> L.) was investigated as a tool for reducing crop potential and for inducing looser clusters that are less susceptible to rot. Fruit set, cluster weight, berry number per cluster, berry size, and cluster compactness were reduced by all defoliation treatments as compared to non-defoliated shoots. Physiological assessment performed in a one-year study on Sangiovese indicated that prebloom removal of the six basal leaves elicited no difference between treatments in mean seasonal assimilation (A) per shoot (2.91 μmol s⁻¹ for control against 2.81 μmol s⁻¹ for the defoliated), a fact due to the offsetting action of more vigorous lateral shoot formation and higher A rates for both main and lateral leaves after veraison in the defoliated shoots. Grape composition was improved by defoliation (higher Brix in both cultivars and higher anthocyanins and phenolics in Sangiovese) as a result of more assimilates being available per unit of cropping and smaller berries characterized by an increased skin-to-pulp ratio. The three-year-study on Trebbiano also showed no carryover effects of defoliation on the following year’s bud differentiation and very few year x treatment interactions, suggesting the prevailing effects of leaf removal over variability because of climate. Overall, early defoliation may be an excellent tool for yield control, replacing time-consuming manual cluster thinning. A time-consistent response suggests that this practice may also improve grape composition.

Identifying neuronal assemblies with local and global connectivity with scale space spectral clustering

A nonparametric approach is proposed to identify clusters of functionally interdependent neurons, independent of the time scale at which they are maximally correlated. The neural point processes are represented in a N-dimensional scale space using the Haar wavelet transform. A similarity measure between any given pair of neurons is defined in the scale space. Clusters of “similar” neurons are identified by first reducing the N-dimensional scale space representation using principal components to obtain a Q-dimensional space. The weighted principal components are subsequently used to connect each neuron to the others in a graph representation. A probabilistic spectral clustering algorithm is used to perform graph partitioning by maximizing cluster compactness. Performance is compared to that of the k-means and the expectation–maximization algorithms for 120 neurons with time-varying intensity functions consisting of spontaneous background activity and phased response elicited at distinct time scales.

Effect of CPPU on Fruit Development of Selected Seedless and Seeded Grape Cultivars

The effects of CPPU [forchlorfenuron, N-(2-chloro-4-pyridinyl)-N-phenylurea] on berry development of Vitis labrusca and V. labrusca × V. vinifera cultivars was evaluated under field conditions. A concentration response was initially established by spraying clusters of `Himrod' at a mean berry diameter of about 5 mm with 0, 5, 10, or 15 mg·L–1 CPPU. Berry enlargement was monitored (16, 30, 44, and 59 days after treatment) during development. Cluster mass, number of berries per cluster, berry mass and firmness, and °Brix were determined at harvest. Berry mass was dramatically increased (2.3 versus about 3.6 g/berry) at harvest by all concentrations of CPPU. Cluster mass and compactness were also increased and berry firmness was linearly related to CPPU concentration (r2 = 0.997). There was no significant effect on number of berries per cluster (79 to 86). °Brix, rachis necrosis at harvest, and berry abscission after 30 days of refrigerated storage (1 °C) were significantly reduced. Effect of time of CPPU application (0, 5, and 10 mg·L–1) was established by treatment of clusters at mean berry diameters of about 4, 5, 7, and 9 mm. Response was indexed by following berry enlargement at 14, 28, 42, and 56 (maturity) days after treatment. Maximum berry size for both 5 and 10 mg·L–1 was obtained from applications at 4 to 7 mm berry diameter. Relative response of seedless and seeded cultivars was compared by application of CPPU at 0, 5, 10, or 15 mg·L–1 to clusters (4 to 6 mm berry diameter) of seedless `Vanessa' and `Lakemont' and seeded `Concord' and `Niagara'. Bioresponse was determined by a time course of berry enlargement and berry and cluster mass, number of berries per cluster, and rating cluster compactness at maturity. Except for `Lakemont' at the 5 mg·L–1 concentration, CPPU at all concentrations increased seedless berry diameter significantly from the first measurement at 14 through 56 days after application. Berry and cluster mass and cluster compactness were significantly increased in `Vanessa'. In contrast, the only effect of CPPU on the two seeded cultivars was an increase in berry size in `Concord' and an initial increase in berry size 14 days after application in `Niagara'.

PHOTOSYNTHETIC INHIBITION OF 'SEYVAL BLANC' GRAPEVINES WITH TERBACIL

PHOTOSYNTHETIC INHIBITION OF 'SEYVAL BLANC' GRAPEVINES WITH TERBACIL

Biological control of Lobesia botrana (Lepidoptera: Tortricidae) larvae by using different formulations of Bacillus thuringiensis in 11 vine cultivars under field conditions.

This work describes the results of an experiment that was conducted in the vineyard of the American Farm School, Thermi, Thessaloniki Greece, during 2001. Its aim was to study the efficacy of two formulations of Bacillus thuringiensis Berliner (wettable powder and dust) to control the larvae of Lobesia botrana Denis & Schiffermueler (Lepidoptera: Tortricidae). The experimental results showed that the two formulations of B. thuringiensis are significantly more effective than the control, the dusting being more effective in most cultivars (Asyrtico, Sauvignon blanc, Debina, Athiri, Agiorgitico, Limnio, Syrah, and Cabernet sauvignon), and the spraying in a few cultivars (Xinomavro, Roditis, and Chardonnay). Dusting in the blue-black cultivars was found to be more effective than spraying, this not being the case in the yellow-green cultivars. This fact should be taken into consideration when cultivars of different color were planted in the same field. Single dusting proved to be better in cultivars with loose, average and dense berry cluster compactness, whereas double spraying gave better results in compact cultivars.

Effect of rearrangement on simulated particle packing

Particle rearrangement is simulated by randomly rolling each particle across its neighbor's surface. The degree of particle rearrangement per particle condensation controls cluster compactness. Two types of rearrangement are studied: rearrangement during condensation and rearrangement after condensation. We find that rearrangement during condensation achieves higher packing density (e.g. high average coordination number (CN)) than rearrangement after condensation at the expense of coordination number uniformity. We find a region of instability in a binary packing system when large particles are added to small particles. This instability zone has variable, lower packing density regions which disappear with rearrangement.

Early stages of silicon nitride film growth studied by molecular dynamics simulations

The molecular dynamics method is used to simulate silicon nitride film growth through atomic deposition on an amorphous silicon surface, which is modeled by the stochastic classical trajectory-ghost theory. For the first time, realistic semi-empirical interatomic potential including both two-body and three-body interactions is employed to calculate the forces among deposited atoms. By the simulation we studied growth kinetics and the effects of substrate temperature and kinetic energy of vaporized atoms on the film growth. It is found that the film growth follows power law mechanism but with two different growth exponents in different growth stages, and changes of the substrate temperature and atomic kinetic energy lead to various film morphologies. This provides a possibility to precisely control the film properties, especially cluster size and compactness, by choosing suitable deposition parameters.

Multi-ionization cross-sections of small ionic carbon clusters by particle impact as a tool to investigate their shapes

Single, double and triple ionization cross-sections of C n + clusters in collisions with helium atoms at intermediate velocity (2.6 a.u.) have been measured ( n = 1 → 5). The relative multi-ionization cross-sections (double over single and triple over single) are first increasing with n, then decreasing when going from n = 4 to n = 5. We show, on the basis of an independent atom and electron collisional treatment, that this effect is attributable to a change in the cluster shape. The role of the cluster compactness on relative multi-ionization cross-sections is pointed out here for the first time.

Polarized infrared study on the structure of two-dimensional nanoclusters of partially fluorinated long-chain fatty acid salts at ambient and elevated temperatures

Atomic force microscopy (AFM) images of the single monolayer of five partially fluorinated fatty acid salts [CF3(CF2)m(CH2)nCOO−]2Cd2+ [(m,n)=(7,10), (7,16), (7,22), (5,22), and (3,22)] transferred from aqueous Cd2+ subphase to solid substrate revealed that the molecules had assembled into monodispersed two-dimensional clusters of tens of nanometers, whose morphology developed systematically with (m,n). Polarized infrared measurements detected a corresponding change with (m,n) in the –(CF2)–m and –(CH2)–n orientation angles. It is found that the van der Waals interaction between the C–C–C trans zig–zag planes of adjacent hydrocarbon segments is the driving force for the cluster formation, while the overlapping interaction between the fluorocarbon tails of neighbor salt molecules is responsible for cluster compactness. Grazing incidence reflection absorption spectra of the (m,n)=(7,10) single monolayer recorded during temperature elevation from 25 to 150 °C show that heating has caused the hydrocarbon chain and the terminal C–CF3 axis to be gradually randomly oriented, while the carboxylate C2 symmetry axis and the fluorocarbon long axis to realign toward the substrate normal. It is discovered that the single monolayer has thermal memory and cyclic heating-cooling treatment can render an excellent thermal stability of 120 °C to the –(CH2)–10 and CF3(CF2)–7 orientations. The different thermal behavior of the corresponding five-layer Y-type LB films, reported by Naselli, Swalen, and Rabolt [J. Chem. Phys. 90, 3855 (1989)] was explained as due to the longitudinal interaction between the headgroups of adjacent layers.

581 Effect of CPPU on Fruit Development in Seedless and Seeded Grape Cultivars

The effect of CPPU [forchlorfenuron; N-(2-chloro-4-pyridinyl)-N-phenylurea] on berry development of selected seedless and seeded grape cultivars was evaluated under field conditions. A concentration response curve was initially established by spraying clusters of `Himrod' at a mean berry diameter of 5 mm with 0, 5, 10, and 15 ppm CPPU. Berry enlargement was monitored (16, 30, 44, and 59 days after treatment) during development and cluster weight, berry number/cluster, weight, firmness and °Brix were determined at harvest. Berry size was dramatically (2.3 vs. about 3.6 g/berry) increased at harvest by all concentrations of CPPU; the response being linearly related to concentration (r2 = 0.89). Cluster weight and compactness (rated) and berry firmness were significantly increased. There was no significant effect on berry number (79 to 86/cluster). °Brix and rachis necrosis (at harvest) as well as berry abscission after 30 days of refrigerated storage were significantly reduced. Effect of time of CPPU application (0, 5, and 10 ppm) was established by treatment of clusters at mean berry diameters of 4, 5, 7, and 9 mm. Response was indexed by following berry enlargement at 14, 28, 42, and 56 (maturity) days after treatment. Maximum berry enlargement for both 5 and 10 ppm was obtained from applications at 4 to 7 mm in diameter. Relative responsiveness of seedless and seeded cultivars was compared by application of CPPU at 0, 5, 10, and 15 ppm to clusters (4–6 mm berry diameter) of seedless `Himrod', `Vanessa' and `Lakemont' and seeded `Concord' and `Niagara'. Bioresponse was determined by a time course of berry enlargement and berry and cluster weight, number of berries/cluster and rating cluster compactness at maturity. CPPU at all concentrations increased seedless berry diameter significantly from the first measurement at 14 days through 56 days after maturity. Berry and cluster weight and cluster compactness were increased in the seedless cultivars, although `Lakemont' appeared less responsive than `Himrod' and `Vanessa'. CPPU did not change (`Lakemont') or decreased (`Himrod', `Vanessa') berries/cluster. In contrast, the only effect of CPPU on the seeded cultivars was an initial increase in berry diameter 14 days after application.

A theory of proximity based clustering: structure detection by optimization

In this paper, a systematic optimization approach for clustering proximity or similarity data is developed. Starting from fundamental invariance and robustness properties, a set of axioms is proposed and discussed to distinguish different cluster compactness and separation criteria. The approach covers the case of sparse proximity matrices, and is extended to nested partitionings for hierarchical data clustering. To solve the associated optimization problems, a rigorous mathematical framework for deterministic annealing and mean-field approximation is presented. Efficient optimization heuristics are derived in a canonical way, which also clarifies the relation to stochastic optimization by Gibbs sampling. Similarity-based clustering techniques have a broad range of possible applications in computer vision, pattern recognition, and data analysis. As a major practical application we present a novel approach to the problem of unsupervised texture segmentation, which relies on statistical tests as a measure of homogeneity. The quality of the algorithms is empirically evaluated on a large collection of Brodatz-like micro-texture Mondrians and on a set of real–word images. To demonstrate the broad usefulness of the theory of proximity based clustering the performances of different criteria and algorithms are compared on an information retrieval task for a document database. The superiority of optimization algorithms for clustering is supported by extensive experiments.

Effectiveness of vacuum impregnation brining of Manchego-type curd

Abstract Salt gain in brining of calf rennet coagulated uncooked pressed curds (20% ewe's and 80% cow's milk), using conventional brine immersion and brine vacuum impregnation, was analysed and compared as a function of the curd size, the curd ageing time and the relative position of the curd sample to the plunger press. Vacuum impregnation implied an additional salt gain of 0.005 g NaCl per g of curd due to hydrodynamic mechanism action, independently from the curd size. Additional diffusional salt gains seemed to be reached by promotion of the effective diffusion associated with brine penetration. The degree of compactness of the casein clusters in curd increased with the distance to the plunger press and the curd ageing time. This greatly affected the brine vacuum impregnation effectiveness related with hydrodynamic mechanisms in the great extra-micellar porosity.

Numerical study of critical behaviour of deformation and permeability of fractured rock masses

The connectivity of fractures in rock masses is determined using a numerical simulation method. There is a continuous fracture cluster throughout a fractured rock mass if fracture density ( d) is at or above a threshold fracture density d c , Fractal dimension ( D f ) is used to describe the connectivity and compactness of the largest fracture clusters. D f increases with increasing fracture density. Percolation theory is used to determine the universal law, D f = A f ( d− d c ) f, which describes the critical behaviour of connectivity of fractures in rock masses. The results from numerical modeling show that the deformability of fractured rock masses increases greatly with increasing fracture density (i.e., fractal dimension), and the critical behaviour of deformability can be described by B s = A( d− d f ) s. Also, the overall permeability of a fractured rock mass occurs at or above a critical fracture density ( d c ) and increases with increasing fracture density. The critical behaviour of permeability can be described by q = A p ( d− d c ) p. The critical behaviour of connectivity and permeability of naturally fractured rock masses is examined using the universal forms.

Vine Management Systems Affect Yield, Fruit Quality, Cluster Compactness, and Fruit Rot of `Chardonnay' Grape

Three vine management systems were evaluated on `Chardonnay' grapevines under Michigan growing conditions for five growing seasons to determine their influence on yield, fruit quality, cluster compactness, and the incidence and severity of fruit rot. These systems used mid-wire cordon (MWC) vine training, Umbrella Kniffin (UK) vine training, and a combination of those (UK/MWC). Over four growing seasons the UK and UK/MWC treatments had higher fruit soluble solids and higher yields than the MWC treatment. These higher yields were attributed to higher yields per node and the ability to retain more live nodes per vine than was possible with the MWC treatment. The UK and UK/MWC treatments also had less fruit rot than the MWC treatment in some years, which was related to reduced compactness of clusters. The UK and UK/MWC treatments produced greater numbers of mature canes per vine than the MWC treatment, and the locations of the canes allowed full cropping the season following an extremely cold winter.

Percolation and cluster structure parameters: The radius of gyration

The squared radius of gyration of percolation clusters are determined in terms of the clusters' second spatial moments using the enhanced Hoshen - Kopelman algorithm for square and triangular lattices containing sites. Correlation length exponents and related exponents as well as their corresponding amplitudes are calculated in terms of the squared radius of gyration above and below the percolation threshold. A coefficient for cluster compactness that is based on the squared radius of gyration of a cluster is introduced. That coefficient is compared with a similar coefficient of compactness that is based on the cluster cyclomatic number.

Thermal regime of the grape (&lt;em&gt;Vitis vinifera&lt;/em&gt; L. Syrah grapes) during maturation. Influence of the berry coloration, the compactness degree of the grape and the local wind regime

&lt;p style="text-align: justify;"&gt;The authors present the results of an experimentation realized on Chiraz grapes with the aims to study the thermal regime supported by berries and clusters during their maturation and to determine the main factors responsible for the observed modifications. The results show that two important factors explain these modifications, firstly, the albedo of the berries which is strongly decreasing as a consequence of the light absorption and subsequent coloration of the berries during the veraison phase and secondly, the increase of the cluster compactness. Two thermic parameters allowing the characterization of the thermal regime of the Chiraz grapes have been defined:&lt;/p&gt;&lt;p style="text-align: justify;"&gt;- the thermal sensibility of the clusters towards the wind velocity directly depending on the compactness or aeration degrees of the grapes,&lt;/p&gt;&lt;p style="text-align: justify;"&gt;and&lt;/p&gt;&lt;p style="text-align: justify;"&gt;- the maximum capacity to accumulate heat which is also linked to cluster compactness but essentially depending on the berries coloration.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;The effect of the compactness or aeration degree of the grape on the thermal regime in relation with the local wind regime has also been described. In practice, it would have been better to take attention to any cultural intervention modifying the wind regime around the vine stocks or surrounding the parcel. A photographic method for estimating the compactness degree of the grape clusters on the vine stock has been used.&lt;/p&gt;

Response of `Chardonnay' Grapevines to Training and Crop Control

Growing conditions in Michigan can threaten the yield and acceptable fruit quality of `Chardonnay' grapevines. Three grapevine training systems, mid-wire cordon (MWC), umbrella kniffin (UK), and a combination of the two (MWC-UK) were evaluated under Michigan growing conditions to determine their influence on yield, fruit quality, cluster compactness, incidence and severity of Botrytis bunch rot, and trellis fill. Vines were grown on C3309 rootstock and pruned to 44 nodes per kilogram of cane prunings. The MWC-UK treatment had an additional 30 nodes per vine retained, and the crop level on these nodes was removed after fruitset. Over a 2-year period, UK and MWC-UK trained vines had fruit soluble solids about 1 °Brix higher and yields were 48% and 63% higher than MWC trained vines, respectively. MWC-UK trained vines consistently out-performed MWC trained vines for all variables measured, while UK-trained vines provided an intermediate response.