Impact of Season and Harvester Engine RPM on Pine Wood Damage from Feed Roller Spikes

Harvesters have become a common solution for wood harvesting in coniferous and broadleaved stands. Unfortunately, not every customer will accept logs with damage on the lateral surface of the roundwood caused by feed roller spikes. The extent of the wood damage caused by the spikes of harvester heads depends mainly on the type of feed rollers and tree species. The objective of the study was to investigate the external damage to pine (Pinus sylvestris L.) roundwood from harvester head spikes depending on the season of the year and harvester engine RPM, as well as the significance and potential consequences of such damage. The scope of the study also included an analysis of wood damage depth in three stem sections. The experimental plots selected were all in an 85-year-old pure pine stand. Logging was performed using a Ponsse Beaver harvester with an H60e harvester head manufactured in 2006. The mean depth of wood damage at all the points of measurement was 4.1 mm, while the maximum depth of wood damage totalled 5.3 mm. The depth of wood damage depended on the season of the year in which the logging work was performed, the harvester engine RPM and the stem section from which the log was processed. The damage was the deepest during summer operations and the shallowest during winter and springtime. The differences were statistically significant, however, the difference in the depth of damage was only 1 mm in average. Deeper wood damage was found at a lower engine RPM. Wood damage depth differed axially, and the least damage was found in the bottom logs

The role of localization in glasses and supercooled liquids

This is the publisher's version, also available electronically from http://scitation.aip.org/content/aip/journal/jcp/104/13/10.1063/1.471147.Localized excitations (tunneling modes, soft harmonic vibrations) are believed to play a dominant role in the thermodynamics and transport properties of glasses at low temperature. Using instantaneous normal‐mode (INM) analysis, we explore the role that such localization plays in determining the behavior of such systems in the vicinity of the glass transition. Building on our previous study [Phys. Rev. Lett. 74, 936 (1995)] we present evidence that the glass transition in two simple model systems is associated with a transition temperature below which all un‐ stable INM’s become localized. This localization transition is a possible mechanism for the change in diffusion mechanism from continuous flow to localized hopping that is believed to occur in fragile glass formers at a temperature just above T g

Investigation of Log Length Accuracy and Harvester Efficiency in Processing of Oak Trees

Harvester use in broadleaves has recently become more effective economically. However, difficulties with delimbing have shown that not all harvesting heads are suitable and efficient for broadleaved species. The typical obstacles are mainly large tree sizes, bends and forks in the trunks and large branches. For these reasons, it is difficult to obtain specific log lengths according to the settings in the harvester on-board computer. The objective of the research was to determine: 1) the accuracy of the log lengths from the bottom, middle and top parts of oak trees, and 2) harvester efficiency in the utilisation of the trunk for logs. The research was carried out on 61-year-old oaks from which logs with an expected length of 250 cm were processed. To achieve this length, a margin of error was set in the harvester computer with minimum and maximum lengths of 252 and 257 cm. For thinning operations, a Ponsse Ergo harvester with a H7 harvesting head was used. After harvesting, manual log measurements were carried out on 280 logs: 69, 142 and 69, from bottom, middle and top parts of the trees, respectively. The largest share of assortments satisfying the minimum requirement of 250–257 cm was obtained from the middle part of the trees (93%), followed by bottom logs (91%) and top logs (88%). The highest frequency of logs, which were too short, were found to be the top logs (9%), while bottom logs were most often too long (6%); therefore, different length settings should be applied to limit such inaccuracies. Analysis of the last log from the highest part of the tree indicated a strong goodness of fit between the top diameter and the DBH; the mean value of the top diameter was 13.3 cm over bark

Determining Harvester Productivity Curves of Thinning Operations in Birch Stands of Central Europe

Silver birch (Betula pendula Roth) is a popular tree species forming stands in nearly the whole of Europe. In Poland, birch is one of the most representative broadleaved species growing on rather poor soils, very often as a mix species with Scots pine (Pinus sylvestris L.). In Central Europe, birch forms trunk often with sweeps, and at the older age with thick branches. Due to that, a harvester thinning operation in birch stands can be challengeable when trying to process logs from the top part of trees, which can finally impact on productivity. The objective of this research was to determine harvester productivity for birch with particular attention to production of logs from the top part of a tree. The research was carried out in stands of North and North-West Poland. All together 21 tests were completed in 16 stands, in which 9 harvesters were used (8 different models). The mean diameter of harvested trees was 23.7 cm with the mean height of 21.7 m. Obtained productivity without delays was on average 21.98 m3 h-1 and varied from as low as 5.14 to maximum 44.66 m3 h-1, and depended mainly on harvested tree size. It was also confirmed that top diameter of the last log depended on diameter at breast height (DBH). The model developed based on that relationship can be used for prediction of biomass volume from birch stands when harvesters are used for thinning

Entropy, Dynamics and Instantaneous Normal Modes in a Random Energy Model

It is shown that the fraction f of imaginary frequency instantaneous normal modes (INM) may be defined and calculated in a random energy model(REM) of liquids. The configurational entropy S and the averaged hopping rate among the states R are also obtained and related to f, with the results R~f and S=a+b*ln(f). The proportionality between R and f is the basis of existing INM theories of diffusion, so the REM further confirms their validity. A link to S opens new avenues for introducing INM into dynamical theories. Liquid 'states' are usually defined by assigning a configuration to the minimum to which it will drain, but the REM naturally treats saddle-barriers on the same footing as minima, which may be a better mapping of the continuum of configurations to discrete states. Requirements of a detailed REM description of liquids are discussed

Estimating and Modelling Harvester Productivity in Pine Stands of Different Ages, Densities and Thinning Intensities

In economic terms, the main limiting factors in harvester application in thinning operations are the stand age and thinning intensity with respect to tree size. Furthermore, harvested mean tree size depends on initial stand density but also on the number of trees cut per hectare. The objective of the research was to estimate the impact of: Þ stand age (class), Þ increasing stand density in each age class (AC), Þ increasing number of trees for harvesting in each AC, Þ thinning intensity, on harvester productivity. 17, 19 and 20 sample plots were established within 3rd (AC3) 4th (AC4) and 5th (AC5) age classes, respectively. In each AC, sample plots were selected that had an increasing number of trees per hectare: 563÷1603, 323÷868 and 476÷836 trees ha–1, in AC3, AC4 and AC5, respectively. Also, in each AC, an increasing number of trees per hectare for harvesting was selected: 130÷853, 80÷315 and 108÷282, in AC3, AC4 and AC5, respectively, with the relevant increasing thinning intensity: 35÷84, 21÷77 and 34÷88 m3 ha–1. In each AC, the stands were divided according to different thinning intensity (THI): a60 m3 ha–1, respectively. A Komatsu 931.1 harvester was used for the thinning operation in each stand. The lowest mean productivity was observed in AC3 (18.57 m3 h–1), which was statistically different to AC4 and AC5 (22.24 and 22.60 m3 h–1, respectively). Within each AC, productivity lowered as the number of trees per hectare increased in the initial stand. The productivity decreased in AC3 and AC5 with the increasing number of trees for harvesting, which was not the case in AC4. In relation to the THIs, the lowest mean productivity was obtained in THIa (16.19 m3 h–1), which was statistically different to THIb and THIc (21.44 and 21.98 m3 h–1, respectively). An increasing THI only influenced productivity positively in AC4 and AC5. It can be concluded that the productivity of the Komatsu 931.1 harvester increased along with: Þ older AC, Þ decreasing number of trees in the initial stand in each AC, Þ lowering number of trees for harvesting in AC3 and AC5, Þ increasing THI in only AC4 and AC5. Finally, in the present model, the larger the mean DBH of the trees for harvesting, the greater the productivity. However, the mean DBH has to be considered in conjunction with the number of trees for harvesting (which depends on AC and THI, as variables in the model) when productivity is analysed

Saddles in the energy landscape probed by supercooled liquids

We numerically investigate the supercooled dynamics of two simple model liquids exploiting the partition of the multi-dimension configuration space in basins of attraction of the stationary points (inherent saddles) of the potential energy surface. We find that the inherent saddles order and potential energy are well defined functions of the temperature T. Moreover, decreasing T, the saddle order vanishes at the same temperature (T_MCT) where the inverse diffusivity appears to diverge as a power law. This allows a topological interpretation of T_MCT: it marks the transition from a dynamics between basins of saddles (T>T_MCT) to a dynamics between basins of minima (T<T_MCT).Comment: 4 pages, 3 figures, to be published on PR

Analytic computation of the Instantaneous Normal Modes spectrum in low density liquids

We analytically compute the spectrum of the Hessian of the Hamiltonian for a system of N particles interacting via a purely repulsive potential in one dimension. Our approach is valid in the low density regime, where we compute the exact spectrum also in the localized sector. We finally perform a numerical analysis of the localization properties of the eigenfunctions.Comment: 4 RevTeX pages, 4 EPS figures. Revised version to appear on Phys. Rev. Let

Impact of Season and Harvester Engine RPM on Pine Wood Damage from Feed Roller Spikes

Harvesters have become a common solution for wood harvesting in coniferous and broadleaved stands. Unfortunately, not every customer will accept logs with damage on the lateral surface of the roundwood caused by feed roller spikes. The extent of the wood damage caused by the spikes of harvester heads depends mainly on the type of feed rollers and tree species. The objective of the study was to investigate the external damage to pine (Pinus sylvestris L.) roundwood from harvester head spikes depending on the season of the year and harvester engine RPM, as well as the significance and potential consequences of such damage. The scope of the study also included an analysis of wood damage depth in three stem sections. The experimental plots selected were all in an 85-year-old pure pine stand. Logging was performed using a Ponsse Beaver harvester with an H60e harvester head manufactured in 2006. The mean depth of wood damage at all the points of measurement was 4.1 mm, while the maximum depth of wood damage totalled 5.3 mm. The depth of wood damage depended on the season of the year in which the logging work was performed, the harvester engine RPM and the stem section from which the log was processed. The damage was the deepest during summer operations and the shallowest during winter and springtime. The differences were statistically significant, however, the difference in the depth of damage was only 1 mm in average. Deeper wood damage was found at a lower engine RPM. Wood damage depth differed axially, and the least damage was found in the bottom logs

Instantaneous Normal Mode Analysis of Supercooled Water

We use the instantaneous normal mode approach to provide a description of the local curvature of the potential energy surface of a model for water. We focus on the region of the phase diagram in which the dynamics may be described by the mode-coupling theory. We find, surprisingly, that the diffusion constant depends mainly on the fraction of directions in configuration space connecting different local minima, supporting the conjecture that the dynamics are controlled by the geometric properties of configuration space. Furthermore, we find an unexpected relation between the number of basins accessed in equilibrium and the connectivity between them.Comment: 5 pages, 4 figure