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According to the Swedish Timber Measurement Act, measurements affecting payments for wood fuels to landowners must be accurate and precise. In this regard, moisture content is an important quality parameter for wood chips which influences the net calorific value as received and thus the economic value. As standard practice moisture content is determined with the oven-drying method, which is cumbersome to use for deliveries to facilities without drying-ovens, which in turn necessitates that samples are taken elsewhere for measurement. An alternative solution is to use a portable moisture meter. Our aim was to evaluate the precision of a handheld capacitance moisture meter. Accuracy and precision of a capacitance meter was determined in the lab and a calibration function was made. Thereafter, the calibrated moisture meter was compared with the standard method for moisture content determination of truckloads of chips. The capacitance meter showed a moderate accuracy by underestimating moisture content by 6.0 percentage points (pp), compared to the reference method, at a precision of ±3.8 pp (CI 95%). For chips with Mâ>â50%, both accuracy and precision decreased. Calibration increased the accuracy in the follow up study by 3 pp for chips with Mâ

Rut formation caused by logging operations has been recognised as a challenge for Swedish forestry. Frequent traffic with heavy machines on extraction roads, together with a warmer climate, is one of the factors that increases the risk of rut formation in forests. One possible way to control this impact of logging operations is to design and apply decision support tools that enable operators to take sensitive areas into account when planning extraction roads. In this study, 16 different logging sites in south-eastern Sweden were surveyed after clear-cut. Information was collected about extraction roads (i.e. traffic intensity, whether the roads had been reinforced with slash) and ruts. Digital maps such as cartographic depth-to-water (DTW) index and soil type were also examined for any connection to rut positions. Soil type and traffic intensity were found to be significant factors in rut formation, while DTW and slash reinforcement were not. However, the DTW map combined with other information, such as soil type, could contribute to decision support tools that improve planning of extraction roads.

The study compared the effect of chipper type on productivity, power demand, fuel consumption and product quality. Tests were conducted on two commercial chipper models, a disc and a drum chipper. Both chippers had the same diameter capacity, were applied to the same tractor and fed with the same feedstock types. Fifteen replications were conducted per machine and for each of four different feedstock types, reaching a total of 120 tests. The disc chipper had a higher energy efficiency and used 19% less fuel per unit product, possibly due to its simpler design, integrating comminuting and discharge system in one synergic device. In contrast, the drum chipper was 8% more productive, since it cut with the same energy all along the length of its knives. The drum chipper produced smaller chips, with a higher incidence of fines. Feedstock type had a strong effect on productivity, energy efficiency and product quality. The effect of feedstock type was mainly related to piece size, and may be stronger than the effect of chipper type. Further studies should determine the effect of blade wear on the relative performance of the two chipper types.

Cleaning (pre-commercial thinning) costs have increased relative to logging and regeneration costs, creating a desire for rationalisation. Cleaning with robots may be a solution, but automating stem selections requires a decision support system (DSS) capable of rendering acceptable results. The aims were to develop a DSS for automation of individual stem selections in practical cleaning, and to test, using simulations, if it renders acceptable results. Data on 17 young forest stands were used to develop a DSS that selects stems by species, position (including distance and density parameters), diameter, and damage. Six simulations were run, following the DSS, with different target settings for density, percentage of deciduous stems and minimum distance between stems. The results depend on the initial state of the stands, but generally met the requested targets in an acceptable way. On average, the density results deviated by â20% to +6% from the target values, the amount of deciduous stems shifted towards the target values, and the proportion of stems with defined damaged decreased from initially 14â90% to 4â13%. The mean diameter at breast height increased and the minimum allowed distance between stems was never violated. The simulation results indicate that the DSS is operational. However, for implementation in robotics a crucial problem is to automatically perceive the selected attributes, so additional simulations with erroneous data were run. Correct measurements of diameters are less crucial than to find the majority of the trees and the majority of trees with damages.

In silvicultural tending operations like cleaning (pre-commercial thinning), the results are irreversible, so it is important for the decisions to be consistent with the aims for the stand. To enable operational automatic stem selections, a decision support system (DSS) is needed. A previously presented DSS seems to render acceptable cleaning results, but needs further analysis. The aims of the study were to compare the cleaning results of experienced cleaners and DSS simulations when âsimilarâ instructions were given, and to assess the usefulness and robustness of the DSS. Twelve experienced cleaners were engaged to âcleanâ (mark main stems) six areas; each cleaner âcleanedâ two areas. The DSS was used to generate two computer-based cleanings (simulations) of these areas. Four laymen also âcleanedâ one of the areas following the DSS. The density results were significantly affected by the areasâ location, whereas the proportions of deciduous stems and damaged stems were significantly affected by both the areasâ location and method, i.e. manual âcleaningâ and general or adjusted simulation. The study showed that the DSS can be adjusted so that the results are comparable with the cleanersâ results. Thus, the DSS seems to be useful and flexible. The laymenâs results were close to the results of the âgeneralâ simulation, implying that the DSS is robust and could be used as a training tool for inexperienced cleaners. The DSS was also acceptable on a single-tree level, as more than 80% of the main-stems selected in the simulations were also selected by at least one cleaner.

In Swedish forestry, final felling is usually done by a harvester and a forwarder. These machines are heavy and the risk for rutting and soil compaction can be considerable under unfavourable soil conditions. The aim of this study was to evaluate effects of forwarder tyre inflation pressure on rutting and soil compaction after final felling. Three levels of forwarder tyre pressure were studied, 300, 450 and 600 kPa, after 2 and 5 machine passages. The first passage was driven with a 19.7 Mg harvester, and the second to fifth passages with a fully loaded forwarder totalling 37.8 Mg. Rut depths were not significant affected by tyre pressures but increased significantly with the number of machine passages. Soil density was significantly increased by 0.075 Mg mâ3 by the harvester passage. Soil density increased significantly with increasing number of forwarder passages, and tyre pressure did not significantly influence this increase but the interaction between number of forwarder passages and tyre pressure was almost significant. Data suggest that density increases occur earlier in the 600 kPa treatment than in the other treatments. Only parts of an area harvested are trafficked in a normal harvesting operation. Outside the research area approximately 12.5 per cent of the area harvested was covered with ruts. On primary strip roads, which are heavily trafficked, soil compaction cannot be avoided by reducing the tyre pressure. On secondary strip roads, not passed more than once by the forwarder, a low forwarder tyre pressure may reduce soil compaction.

Selective pre-commercial thinning (PCT) is usually carried out by workers with a brush saw in order to increase the growth of the potential crop trees (main stems) through removal of competing trees. In the last decade relative PCT costs have increased, partly because stands are denser and have higher trees when treated, which has led to new interest for mechanised PCT. The objective was to compare mechanised and motor manual PCT regarding productivity and damage to remaining main stems. Time consumption for, and damage after, mechanised and motor manual PCT were studied on 50 plots per treatment in mixed pine birch stands with an initial stand density exceeding 4500 stems haâ1. In the present study productivity was influenced by stand density, stand height and the quota between height and diameter. Irrespectively of these factors, mechanised PCT was 0.74 hours haâ1 slower than motor manual PCT. Motor manual PCT of the average stand (average height 3.69 m, 10 816 stems haâ1) took 5.06 effective hours. In average 2475 and 2805 main stems haâ1 were left after the mechanised and motor manual treatments, respectively, whereof 1.3 and 2.1% were damaged by the treatments. The results show that efficiency in motor manual PCT has increased in dense and tall stands compared to older studies. Motor manual PCT was more time effective than mechanised PCT, and thereby also even more cost-effective. However, the potential for technical and methodological development of mechanised PCT is probably larger than for motor manual PCT.

During the last ten years interest in the harwarder has increased, however, studies have concentrated on effects of technical improvements on machine productivity. It has been noted that there is a large potential to increase the productivity through development of suitable work methods. To find efficient work patterns for a harwarder with a turnable loading area, three different harvesting methods were studied in final felling. Three work methods were used. Method 1: the harwarder drove backwards into the stand making a strip road, strip road trees were felled and left on the ground, on the way out of the stand the harwarder cut and processed the trees on both sides of the machine directly into the loading area. Method 2: the harwarder drove forward along the edge of the cut, cutting and processing trees directly into the loading area. Method 3: the harwarder drove forward into the stand and cut and processed strip road trees and trees standing on both sides of the machine directly into the loading area. The most efficient work method was method 2 where the productivity was 13.0 m3 u.b. per E0h (cubic metre under bark per effective hour). The productivities for method 1 and 3 were 12.1 and 11.9 m3 u.b. per E0h, respectively. In addition to work method harwarder productivity was shown to be dependent on load volume, average tree size and hauling distance. The only work elements significantly affected by work methods were processing and movement during processing. The operator had only a few weeks to get used to the machine and even less time to practise on the work methods. Thus, it is probable that the productivity for the studied methods will increase with increasing work experience. Furthermore, as only three work methods were studied, there are still untested work methods. The potential to further improve harwarder work methods is considerable.

Delivery performance in wood supply chains is affected by carrying capacity on forest roads. Stochastic weather variations affect carrying capacity of roads and accessibility of harvested wood on landings. In Sweden, annual harvest scheduling is usually based on four seasons and road accessibility classes are set to match these seasons. In reality, road accessibility changes depend on weather variations not season. This causes a risk of poor delivery performance. Delivery performance is evaluated using two performance indicators, backorders (orders not delivered on time) and lead time (time from harvesting to delivery to mill). A data-analytic framework, combining optimization and simulation, is proposed to assess and evaluate these performance indicators for the wood supply chain under stochastic weather variations. An optimization model is used to generate a feasible harvest schedule for expected weather. This is thereafter evaluated given various weather scenarios using a discrete-event simulation model. The combination of optimization and discrete-event simulation is used to assess delivery performance over time, and changes in road accessibility caused by weather variation. An expected decrease in road accessibility implies a stable delivery performance, while an unexpected decrease causes a reduced delivery performance. [ABSTRACT FROM AUTHOR]

The Virtual Wood Supply Arena is an on-line training environment for managing roundwood purchase, production and transport in cut-to-length supply systems. The purpose of its development was accelerated training for coordination of these functions under realistic operating conditions. It offers 8- and 12-week scenarios for supplying five mills. Weekly planning is done for 10 harvesting teams and 10 trucks in a Swedish case geography while tracking mill delivery fulfillment under weekly trafficability restrictions. The purpose of this paper is to introduce the training environment and report the progression of student performance after 2 years of use in university-level training. Student teams reached full delivery fulfillment within three training runs. After familiarization during an introductory run, a complete 12-week scenario took four effective hours to complete. Delivery fulfillment increased from 82 to 95 and 100% between the first, second and third training runs. The progression of team performance included a 36% reduction of relocation distances for harvesting teams and 11% reduction of transport distances for hauling from forest to mill. By the third training run these performance levels were attained with less than 2 weeks of inventory for both the purchase bank and roadside stocks. [ABSTRACT FROM AUTHOR]

Fuel consumption is an important factor affecting both costs and environmental impact of a logging operation. Traditionally, fuel consumption has been estimated through studies of individual machines, through follow-up studies based on company records or through questionnaires. Using automatically collected data from machine computers, in the form of standardized harvester production (hpr), forwarder production (fpr), and machine operational monitoring (mom) files, offers a new way to estimate fuel consumption. This study aims to estimate fuel consumption in cut-to-length logging operations based on automatically recorded data, and to evaluate whether this data is sufficient on its own or needs to be supplemented with additional data. Average fuel consumption per harvested m3 varied from 1.4 to 3.4 l, depending on machine size, tree size, and transport distance. The study shows that fuel consumption per machine type or logging team can largely be explained using the machine data. Classification of machines into size classes is a challenge, as machine configurations vary between individual machines, but such classification may not be needed. Forwarded volumes are a source of error, since this data is manually fed into the machine computer and, therefore, often deviates from the felled volume in a harvesting block. This will probably cause a slight overestimation of forwarder fuel consumption. [ABSTRACT FROM AUTHOR]

The aim of this study was to measure and model the fuel consumption of cut-to-length (CTL) logging machinery in cutting and forwarding under Nordic harvesting conditions, and to clarify which factors had the greatest effect on the fuel consumption. In addition, the total annual fuel consumption and CO2eq emissions were calculated for CTL logging operations in Finland in 2020. The data were collected during a long-term follow-up study on the fuel consumption of harvesters and forwarders conducted between March 2018 and April 2019. The fuel consumption data were obtained from a total of 16 harvesters and 13 forwarders equipped with digital flow metres featuring an accuracy of ± 1% of the fuel volume measured. The engine power of the forest machines explained most of the hour-based fuel consumption. Correspondingly, the harvesting conditions of the forest stand best explained the cubic-metre-based fuel consumption. The fuel consumption of CTL logging operations (cutting and forwarding) averaged 1.4 L m−3 in final felling, and 3.1 and 2.2 L m−3 in first and later thinning, respectively. There was a large variation in the cubic-metre-based fuel consumption between individual machines, both for harvesters and forwarders. The total calculated fuel consumption in Finnish CTL operations in 2020 was 126.6 million L, with the calculated CO2eq emissions totalling 334,209 t (i.e. 5.7 kg m−3). Several measures to accelerate fuel and energy efficiency and reduce CO2eq emissions in CTL logging operations are discussed in the paper. [ABSTRACT FROM AUTHOR]

The PicUp3D code is a prototype of simulation software dedicated to quantitative and accurate modeling of spacecraft plasma interactions developed in the context of a European scientific and industrial network Spacecraft Plasma Interaction Network in Europe. It is based on a full three-dimensional kinetic particle-in-cell description of the electrons and the ion dynamics. The use of unstructured schemes in the spacecraft geometrical description has allowed to model successfully realistic geometries. The code is organized around an open and versatile object-oriented library and is fully written in JAVA. This paper presents the basic features and the first validation tests of PicUp3D, which are now made publicly and freely available on the Web. Developed in an open-source approach, it is believed that this code will meet the requirements of the scientific community in terms of geometric and physics accuracy especially for instrument calibration and observation analysis. Index Terms--Charging, finite-differences, JAVA, object oriented, particle in cell (PIC), spacecraft plasma interaction.

Sieving of chipped forest fuels has recently been suggested as a way to reduce dry matter losses during storage. Sieving provides a more homogeneous acceptable material with better storage properties, which reduces the risk of energy and dry matter losses and spontaneous ignition. Screened chips can be priced higher due to better quality, and both acceptable and reject fractions are more homogeneous, which improves combustion control. Sieving is costly and the reject fraction is not suitable for storage. Five sieving operations were studied, three involving vibrating screens and two involving starscreens. On average, starscreens were more productive than vibrating screens. In all operations, the sieving machine limited productivity, and the loader feeding the machine was not fully utilized. Sieving costs were under two euro per MWh of chips, which may be recovered through higher values and lower storage losses in the acceptable fraction. If sieving operations were used to increase storage of chips, it could increase the annual utilization of chippers and chip trucks in the supply chain, thereby reducing supply costs. Profitable sieving operations require demand for the fine fraction at a price close to that of residue chips. [ABSTRACT FROM AUTHOR]