Tree Length Research Articles

Coconut Shell Powder and Electrical Tree Inhibition of Solid Insulator

Electrical tree phenomenon commonly occurred in solid insulator material resulting from the inconsistency of stresses during the manufacturing process. The treeing phenomenon will degrade the characteristic of insulator and may lead to breakdown. The use of filler in the manufacturing process in order to enhancing the insulation property is a popular approach. This paper presents the use of coconut shell powder (CSP) filler in epoxy resin for inhibition of electrical tree growth. The particle sizes of CSP varied from 62, 75 and 125 µm. The CSP is filled with the ratio of 0.1, 0.2, 0.4, 0.6, 0.8, 1.0, 2.0 and 3.0% by weight. We aim to observe the effects of varying the combination of CSP particle sizes and the ratio of epoxy resin for an inhibition of electrical tree growth. The electrical tree was tested by applying AC voltage of 15kV to the test sample and conducted for 360 minutes in this experiment. When the epoxy resin using CSP filler of 1% by weight is fixed for the particle size of 62, 75 and 125 µm, electrical tree length is at 1.24mm, 1.382 mm and 1.78 mm respectively. Whereas, when the particle size of CSP at 62 µm is fixed, a tree length is 1.98 mm and 1.24 mm for the ratio of 0.1 and 1% by weight respectively. Our study demonstrates that the epoxy resin using CSP filler at a ratio of 0.1% by weight can shorten length of electrical tree when compared with a ratio of 1.0% by weight. The electrical tree length was affected through the changes of permittivity by addition of CSP compound.

Morphological Characterization of Ficus religiosa Genotypes in Iran by Multivariate Analysis

Ficus religiosa L. is one of the most popular species in the Moraceae family that is known as a multipurpose forest tree species because of its medicinal, ornamental, and religious value. F. religiosa is an important tree in South Asia, and it possesses various common names such as peepal, bodhi, bo tree, and asvattha. This species as a traditional tree is broadly planted as a roadside tree, and it plays an important role as a medicinal tree in various diseases such as asthma, stomatitis, diabetes, inflammations, glandular swelling disorders, and wound healing. Because F. religiosa is characterized as a subtropical tree, it fully grew in southern parts of Iran. The morphological variation of 72 individuals of F. religiosa from six southern regions of Iran was investigated based on multivariate analysis. Our results indicated that the highest tree, leaf, and petiole lengths, as well as leaf width, were observed in Kish and Qeshm genotypes, whereas the Chabahar genotype had the lowest petiole length. Results of simple correlation analysis showed the existence of significant positive and negative correlations among some important parameters. The highest correlation was observed between leaf, tree, and petiole lengths. Populations were clustered in four groups. The Kish and Qeshm genotypes were closely related to each other and differentiated from the Chabahar genotype. The whole dataset was subjected to principal component analysis (PCA). PCA showed that the first two factor components explained 84.51% of the variation and the first factor component had the positive relationship with leaf, tree, and petiole lengths.

Tree Growth Characteristics of Epoxy Resin in LN2 Under DC Superimposed Pulse Voltage

Chosen as an important insulation material of high temperature superconducting dc cable terminals, epoxy resin needs to address the challenge of the liquid nitrogen (LN 2 ) temperature and various kinds of voltage due to the special operating environment. The switching over voltage, lightning strike, and current impact will introduce the pulse voltage into the operation of the dc equipment, which makes it necessary to study the insulating characteristics of epoxy resin under dc superimposed pulse voltage condition. This paper investigates the electrical tree growth characteristics of epoxy resin with application of dc superimposed pulse voltage in LN 2 . The tested samples were stressed with combined dc-pulse voltage with different amplitudes and polarities in a needle-plate geometry electrode system at -196 °C. Tree length and accumulated damage are employed to characterize the electrical tree. The experimental results indicate that when the dc and pulse voltage are of the same polarity, the rate of tree growth increases with the amplitude of dc voltage rising but would slow down after a period time of treeing. When the polarity of dc and pulse voltage is opposite, the growth rate decreases with the dc voltage amplitude increasing, while it could maintain a relatively high level during the whole treeing time.

DC electrical tree initiation in silicone rubber under temperature gradient

In this paper, initiation behaviors of DC electrical tree in silicone rubber were studied under different voltage polarities and temperature gradients (temperature of needle and ground electrodes ranged from 20 to 120 °C). Electrical tree initiation probability, tree shape, and tree length were obtained via the statistics. The results show that polarity effects, where the positive DC voltage is easier for trees to initiate, appear evidently under various temperature situations. As for the temperature gradient, tree initiation voltage decreases first and then returns to a larger value with the increasing needle temperature when the ground electrode temperature is fixed at 20 °C. Both the probability of multiple-branch tree and corresponding tree length increase and subsequently decrease. However, tree initiation voltage decreases alone and tree length increases with the rise of ground electrode temperature when the needle temperature is fixed at 20 °C. Homo charge injection becomes easier with increasing needle temperature following the Schottky-Richardson approximation under ramped DC voltages. In addition, electric field strength at the tip decreases when the needle temperature is higher than ground temperature, since the conductivity is sensitive to the local temperature and electric field. It is believed that the needle temperature and the temperature gradient dominate tree initiation behaviors, where the former affects the collisional ionization and partial relaxation of silicone rubber chains, and the latter decides electric field distribution in the bulk.

Inverse dynamic and spectral problems for the one-dimensional Dirac system on a finite tree

Abstract We consider inverse dynamic and spectral problems for the one-dimensional Dirac system on a finite tree. Our aim will be to recover the topology of a tree (lengths and connectivity of edges) as well as the matrix potentials on each edge. As inverse data we use the Weyl–Titchmarsh matrix function or the dynamic response operator.

So many genes, so little time: A practical approach to divergence-time estimation in the genomic era.

Phylogenomic datasets have been successfully used to address questions involving evolutionary relationships, patterns of genome structure, signatures of selection, and gene and genome duplications. However, despite the recent explosion in genomic and transcriptomic data, the utility of these data sources for efficient divergence-time inference remains unexamined. Phylogenomic datasets pose two distinct problems for divergence-time estimation: (i) the volume of data makes inference of the entire dataset intractable, and (ii) the extent of underlying topological and rate heterogeneity across genes makes model mis-specification a real concern. “Gene shopping”, wherein a phylogenomic dataset is winnowed to a set of genes with desirable properties, represents an alternative approach that holds promise in alleviating these issues. We implemented an approach for phylogenomic datasets (available in SortaDate) that filters genes by three criteria: (i) clock-likeness, (ii) reasonable tree length (i.e., discernible information content), and (iii) least topological conflict with a focal species tree (presumed to have already been inferred). Such a winnowing procedure ensures that errors associated with model (both clock and topology) mis-specification are minimized, therefore reducing error in divergence-time estimation. We demonstrated the efficacy of this approach through simulation and applied it to published animal (Aves, Diplopoda, and Hymenoptera) and plant (carnivorous Caryophyllales, broad Caryophyllales, and Vitales) phylogenomic datasets. By quantifying rate heterogeneity across both genes and lineages we found that every empirical dataset examined included genes with clock-like, or nearly clock-like, behavior. Moreover, many datasets had genes that were clock-like, exhibited reasonable evolutionary rates, and were mostly compatible with the species tree. We identified overlap in age estimates when analyzing these filtered genes under strict clock and uncorrelated lognormal (UCLN) models. However, this overlap was often due to imprecise estimates from the UCLN model. We find that “gene shopping” can be an efficient approach to divergence-time inference for phylogenomic datasets that may otherwise be characterized by extensive gene tree heterogeneity.

Wpływ zabiegów stymulujących rozgałęzianie na jakość okulantów jabłoni

The objective of the paper was to study the impact of mechanical and chemical treatments stimulating branching on the quality of ‘Gloster’ and ‘Jonagold’ apple tree maidens budded onto the M.9 rootstock. The studies showed that the height of the assessed apple tree maidens was dependent on a cultivar in most combinations and hence, the ‘Gloster’ apple tree maidens were significantly shorter than ‘Jonagold’ cultivar during the intensive growth period in summer. In autumn, on the other hand, an inverse relationship was noted. Throughout the entire vegetative season, no significant influence of the applied treatments was found on height increments, stem diameter of rootstocks and maiden trees or the sum of lateral shoot length of the apple trees under investigation. The Globaryll 100 SL preparation applied three times on ‘Jonagold’ cultivar plants significantly increased the numbers of sylleptic shoots compared to the other combinations. In most combinations, the number of lateral shoots depended significantly on a cultivar.

Research on the discharge characteristics for water tree in crosslinked polyethylene cable based on plasma-chemical model

Water tree is the predominant defect in high-voltage crosslinked polyethylene cables. The microscopic mechanism in the discharge process is not fully understood; hence, a drawback is created towards an effective method to evaluate the insulation status. In order to investigate the growth of water tree, a plasma-chemical model is developed. The dynamic characteristics of the discharge process including voltage waveform, current waveform, electron density, electric potential, and electric field intensity are analyzed. Our results show that the distorted electric field is the predominant contributing factor of electron avalanche formation, which inevitably leads to the formation of pulse current. In addition, it is found that characteristic parameters such as the pulse width and pulse number have a great relevance to the length of water tree. Accordingly, the growth of water tree can be divided into the initial stage, development stage, and pre-breakdown stage, which provides a reference for evaluating the deteriorated stages of crosslinked polyethylene cables.

Intracerebroventricular administration of growth hormone induces morphological changes in pyramidal neurons of the hippocampus and prefrontal cortex in adult rats.

A growing body of evidence suggests that growth hormone (GH) affects synaptic plasticity at both the molecular and electrophysiological levels. However, unclear is whether plasticity that is stimulated by GH is associated with changes in neuron structure. This study investigated the effect of intracerebroventricular (ICV) administration of GH on the morphology of pyramidal neurons of the CA1 region of the dorsal hippocampus and layer III of the prefrontal cortex. Male Wistar rats received daily ICV injections of GH (120 ng) for 7 days, and they were euthanized 21 days later. Changes in neuronal morphology were evaluated using Golgi-Cox staining and subsequent Sholl analysis. GH administration increased total dendritic length in the CA1 region of the dorsal hippocampus and prefrontal cortex. The Sholl analysis revealed an increase in dendritic length of the third to eighth branch orders in the hippocampus and from the third to sixth branch orders in the prefrontal cortex. Interestingly, GH treatment increased the density of dendritic spines in both brain regions, favoring the presence of mushroom-like spines only in the CA1 hippocampal region. Our results indicated that GH induces changes in the length of dendritic trees and the density of dendritic spines in two high-plasticity brain regions, suggesting that GH-induced synaptic plasticity at the molecular and electrophysiological levels may be associated with these structural changes in neurons.

A spatial one-to-many flow layout algorithm using triangulation, approximate Steiner trees, and path smoothing

ABSTRACTMapping spatial flow remains a challenge despite noticeable progress in recent years. This article presents a new, automated layout algorithm for spatial flow from one origin to multiple destinations. The algorithm triangulates the mapped space and builds a network from the triangles. It then simulates the formation of the dendritic drainage pattern of natural river systems and constructs an approximate Steiner tree by sequentially computing the shortest paths from the origin to the destinations using dynamically decreasing edge costs. A series of automatic cartographic operations, including edge simplification, straightening, smoothing, and rendering, then follow to improve the esthetics of the tree and to produce flow layouts that feature natural clusters and smooth edges. An experimental evaluation using four examples illustrates the effectiveness and adaptability of the algorithm with various spatial and parameter configurations. A quantitative comparison with existing methods on esthetics shows that the new algorithm generally renders destinations farther away from tree edges, which helps improve map readability but at the cost of longer total tree length. Evaluated with a smoothness index that rewards gradual tree splitting and smooth, natural, and straight edges, the proposed algorithm can achieve higher average edge smoothness and avoid the least smooth edges under various parameter settings.

Optimizing homeostatic cell renewal in hierarchical tissues.

In order to maintain homeostasis, mature cells removed from the top compartment of hierarchical tissues have to be replenished by means of differentiation and self-renewal events happening in the more primitive compartments. As each cell division is associated with a risk of mutation, cell division patterns have to be optimized, in order to minimize or delay the risk of malignancy generation. Here we study this optimization problem, focusing on the role of division tree length, that is, the number of layers of cells activated in response to the loss of terminally differentiated cells, which is related to the balance between differentiation and self-renewal events in the compartments. Using both analytical methods and stochastic simulations in a metapopulation-style model, we find that shorter division trees are advantageous if the objective is to minimize the total number of one-hit mutants in the cell population. Longer division trees on the other hand minimize the accumulation of two-hit mutants, which is a more likely evolutionary goal given the key role played by tumor suppressor genes in cancer initiation. While division tree length is the most important property determining mutant accumulation, we also find that increasing the size of primitive compartments helps to delay two-hit mutant generation.

Effects of mechanical stretching on electrical treeing characteristics in EPDM

Effects of mechanical stretching, produced after the expansion of cable accessories, on the electrical tree growth characteristics of EPDM (Ethylene Propylene Diene Monomer) are reported in the present work. FFV (fractional free volume) and CED (cohesion energy density), which were respectively related to free path of electrons and molecular chains splitting during electrical tree propagation process, were calculated through molecular dynamics simulations under different stretching ratios. A needle-plane electrode system with the stretching ratio ranging from 0 to 30% was used to investigate the electrical treeing characteristics in the experimental study. The simulation results show that the FFV becomes larger at higher stretching ratio, which enhances the collision between the hot electron and the molecular chain during the treeing process by extending the free path of the hot electron. While CED tends to become smaller at higher stretching ratio, reducing the cohesion strength for the tree channel crack to grow. Moreover, FFV and CED are investigated during the stretching recovery process, where FFV tends to decrease and CED turns to be larger. The experimental results indicate that mechanical stretching affects the electrical tree inception and propagation characteristics. The inception time of electrical tree becomes shorter as stretching ratio increases from 0 to 30%. Tree length and accumulated damage become larger with increasing the stretching ratio. Electrical tree propagation mechanism considering chemical and physical traps, which are generated under mechanical stretching, are also discussed and analyzed.

Compressive stress dependence of electrical tree growth characteristics in EPDM

To ensure a certain interface electrical strength resistance, the cable accessories are densely coated onto the main cable insulation. Compressive stress is generated in the normal direction of high voltage cable by the spring clamp device or the banding force after the expansion of EPDM (Ethylene Propylene Diene Monomer) stress cone. This paper presented a compressive stress experimental study considering electrical treeing propagation in EPDM by employing a needle-plane electrode system. The results indicate that compressive stress affects the electrical tree inception and propagation characteristics. The inception time of electrical tree becomes longer as compressive rate increases from 0 to 30%. Tree length and accumulated damage become smaller with increasing the compressive rate. Electrical tree structure is also depended on compressive stress, and branch tree structure becomes the main electrical tree morphology at higher compressive rate. For better understanding the effects of compressive stress on electrical tree propagation characteristics, FFV (fractional free volume) and CED (cohesion energy density) were calculated and analyzed through molecular dynamics simulations under different compressive rates. Results show that the FFV becomes smaller at higher compressive rate, which shortens the free path of the hot electron and weakens the collision with the molecular chain during the treeing process. While CED tends to be lager under higher compressive rate, which improves the cohesion strength for the crack to grow in the tree channel tips and restrains the propagation of electrical tree.

Arena Function: A Framework for Computing Capacity Bounds in Wireless Networks

Bounds on the capacity of wireless networks often rely on simplifying assumptions and are given in terms of coarse network parameters, such as the number of nodes. While useful due to their simplicity, such bounds can significantly overestimate the achievable capacity in real-world situations, ignoring actual network topology and traffic patterns. The results of this paper improve such analytical results on network capacity in several ways. At the heart of our methodology lies the concept of transmission arenas , which indicates the presence of active transmissions near any given location in the network. This novel space-based approach is well-suited to untangle the interactions of simultaneous transmissions. Avoiding a graph-based model of the network, it opens new avenues of studying capacities. For homogeneous networks, we recover classical bounds. However, our methodology applies to arbitrary networks and can, thus, inform placing and activating of nodes also in the presence of clustering. Our method works with all classical channel models and dimensions. It provides bounds on the transport capacity which involve only high-level knowledge of node locations, such as the length of Euclidean minimum spanning tree. As an additional novelty, we establish bounds on wireless unicast and multicast capacities.

Identifiability of Phylogenetic Parameters from k-mer Data Under the Coalescent.

Distances between sequences based on their k-mer frequency counts can be used to reconstruct phylogenies without first computing a sequence alignment. Past work has shown that effective use of k-mer methods depends on (1) model-based corrections to distances based on k-mers and (2) breaking long sequences into blocks to obtain repeated trials from the sequence-generating process. Good performance of such methods is based on having many high-quality blocks with many homologous sites, which can be problematic to guarantee a priori. Nature provides natural blocks of sequences into homologous regions-namely, the genes. However, directly using past work in this setting is problematic because of possible discordance between different gene trees and the underlying species tree. Using the multispecies coalescent model as a basis, we derive model-based moment formulas that involve the species divergence times and the coalescent parameters. From this setting, we prove identifiability results for the tree and branch length parameters under the Jukes-Cantor model of sequence mutations.

Productivity and cost of a small-scale cable yarder in an uphill and downhill area: a case study in South Korea

ABSTRACTTree diameter, topography, and stand accessibility have been major factors to consider when selecting the optimal equipment to extract logs from stump to landing area. In Korea, forest land has 6.4 million ha of forest, comprising 64% of its total land area. Small and medium (15–30 cm in diameter at breast height [DBH]) size of trees located on steep slopes (> 30°) is approximately 80% of total forest area. Therefore, there has been an increasing interest in the application of a small-scale cable yarding system. We performed uphill and downhill yarding experiments using an 80 hp farm tractor mounted tower yarder (HAM300) to evaluate productivities and costs associated with primary transportation of tree length logs in mixed conifer stands. In addition, sensitivity analyses were performed to find the effects of different yarding directions and distances on yarding productivities and costs. Results showed that uphill and downhill yarding productivities were 9.04 m3/PMH (Productivity Machine Hours) and 7.87 m3/PMH at a cost of US$9.06 and US$10.04/m3, respectively. The yarding direction greatly affected productivity and cost: decreasing productivity may be significantly affected by working conditions. Our results support the effectiveness of an HAM300 yarder in extracting logs for small-scale cable yarding operations.

Pengaruh Waktu Perendaman dan Konsentrasi Giberelin (GA3) pada Pertumbuhan Benih Cemara Laut (Casuarina equisetifolia L.)

Gibberellin (GA 3 ) is a natural growth hormone and synthesis used to break dormancy and accelerate germination and growth processes. The purpose of this study is to determine the effect of gibberellin concentration (GA 3 ), soaking duration , and the interaction between gibberellin concentration (GA3) and soaking duration on the growth of australian pine tree seed. The research was conducted in State Polytechnic of Lampung from October 2015 to February 2016. This research used Factorial Randomized Block Design (R BD ). The first factor i s the concentration of gibberellin (GA 3 ) namely A 0 (without GA 3 ), A 1 (1000 mg.l -1 GA 3 ), A 2 (1250 mg.l -1 GA 3 ), and A 3 (1500 mg.l -1 GA 3 ) . T he second factor is the soaking duration of GA 3 namely B 1 (soaking for 3 hours), B 2 (soaking for 6 hours), and B 3 (soaking for 9 hours). The result showed that GA 3 at concentration 1500 mg.l -1 increase d germination, the percentage of germinated seeds, hypocotyl diameter, hypocotyl length, growth homogenity, and vigor of australian pine tree seed. S oaking duration for 9 hours can increase germination, the percentage of germinated seeds, hypocotyl diameter, hypocotyl length, growth homogeneity, and australian pine tree seed vigor. The interaction between GA 3 concentration at 1500 mg.l -1 and the soaking duration for 9 hours increase d the germination, the percentage of germinated seeds, hypocotyl diameter, hypocotyl length, growth homogeneity, and australian pine tree seed vigor. Keywords: Casuarina equisetifolia L., gibberelin, seed vigor, soaking duration Permalink: http://jurnal.polinela.ac.id/index.php/AIP/article/view/649

Modelling of information diffusion on social networks with applications to WeChat

Traces of user activities recorded in online social networks open new possibilities to systematically understand the information diffusion process on social networks. From the online social network WeChat, we collected a large number of information cascade trees, each of which tells the spreading trajectory of a message/information such as which user creates the information and which users view or forward the information shared by which neighbours. In this work, we propose two heterogeneous non-linear models, one for the topologies of the information cascade trees and the other for the stochastic process of information diffusion on a social network. Both models are validated by the WeChat data in reproducing and explaining key features of cascade trees.Specifically, we apply the Random Recursive Tree (RRT) to model the growth of cascade trees. The RRT model could capture key features, i.e. the average path length and degree variance of a cascade tree in relation to the number of nodes (size) of the tree. Its single identified parameter quantifies the relative depth or broadness of the cascade trees and indicates that information propagates via a star-like broadcasting or viral-like hop by hop spreading. The RRT model explains the appearance of hubs, thus a possibly smaller average path length as the cascade size increases, as observed in WeChat. We further propose the stochastic Susceptible View Forward Removed (SVFR) model to depict the dynamic user behaviour including creating, viewing, forwarding and ignoring a message on a given social network. Beside the average path length and degree variance of the cascade trees in relation to their sizes, the SVFR model could further explain the power-law cascade size distribution in WeChat and unravel that a user with a large number of friends may actually have a smaller probability to read a message (s)he receives due to limited attention.

Ground-dwelling arthropod response to fire and clearcutting in jack pine: implications for ecosystem management

We tested the response of species composition of three dominant litter-dwelling arthropod taxa (carabid beetles, spiders, and rove beetles) to wildfire and harvest. This study was conducted in north-central Ontario (47°42′N, 83°36′W) in jack pine (Pinus banksiana Lamb.) dominated stands in 2013 using pitfall trapping. Using 222 species (12 015 individuals), we compared the effects of disturbance using recently burned (3 years since fire) and clearcut sites (3 years since harvest; tree length, full tree, stump removal, and blading), as well as older, closed-canopy stands that have regenerated following clearcutting (51 years since harvest) and fire (92 years since fire), with multivariate regression trees. Taxa were more similar in the three controls (including recent fire) than between controls and harvest treatments, with increased forest floor disturbance in harvested plots being a likely explanation. In addition, taxa were different in the younger (51 years) harvest-origin plots than in the older (92 years) fire-origin plots, suggesting that communities had not yet recovered from the harvest disturbance possibly due to insufficient coarse woody debris in the younger stand. These results indicate that forest management practices that match natural forest floor disturbance could ameliorate short-term effects, whereas the maintenance of more coarse woody debris could reduce the recovery time of epigaeic communities.

Maintenance of carbohydrate transport in tall trees.

Trees present a critical challenge to long-distance transport because as a tree grows in height and the transport pathway increases in length, the hydraulic resistance of the vascular tissue should increase. This has led many to question whether trees can rely on a passive transport mechanism to move carbohydrates from their leaves to their roots. Although species that actively load sugars into their phloem, such as vines and herbs, can increase the driving force for transport as they elongate, it is possible that many trees cannot generate high turgor pressures because they do not use transporters to load sugar into the phloem. Here, we examine how trees can maintain efficient carbohydrate transport as they grow taller by analysing sieve tube anatomy, including sieve plate geometry, using recently developed preparation and imaging techniques, and by measuring the turgor pressures in the leaves of a tall tree in situ. Across nine deciduous species, we find that hydraulic resistance in the phloem scales inversely with plant height because of a shift in sieve element structure along the length of individual trees. This scaling relationship seems robust across multiple species despite large differences in plate anatomy. The importance of this scaling becomes clear when phloem transport is modelled using turgor pressures measured in the leaves of a mature red oak tree. These pressures are of sufficient magnitude to drive phloem transport only in concert with structural changes in the phloem that reduce transport resistance. As a result, the key to the long-standing mystery of how trees maintain phloem transport as they increase in size lies in the structure of the phloem and its ability to change hydraulic properties with plant height.