Comminution of Logging Residues with Evolution 910R chipper, MOHA chipper truck, and Morbark 1200 tub grinder

This study is part of the ongoing national Bioenergy Research Programme in Finland. The study looked into the quality of chips made of logging residues composed predominantly of spruce wood. In addition, the productivity of the Evolution 910R chipper, the MOHA chipper truck, and the Morbark 1200 tub grinder was studied. The three machines studied were capable of producing acceptable chips for heat generation plants. The particle-size distribution was good in all cases and the proportion of large particles and the fine fraction was small. The ash content of the chips was low due to carefulness in the handling of logging residues. The moisture content was typical for logging residues stored at the logging site for some months. The machine productivity values obtained were as follows: Evolution = 65 m3 loose/E15-h, MOHA = 23 m3 loose/E15-h, and Morbark = 5060 m3 loose/E15-h. These results are preliminary; a follow-up study is needed for more reliable results to be obtained concerning the productivities

Influence of Small Control Levers of Grapple Loader on Muscle Strain, Productivity and Control Errors

Small-sized mini-levers were compared to conventional levers in forwarder grapple loading of timber using a forest machine simulator in clear-cutting and thinning conditions. No effect on time consumption per burden was observed, but muscle constriction in the trapezius muscle measured using EMG was lower when the mini-lever option was used. Control errors were measured by counting the contacts between the remaining trees and the machine elements. These were interpreted to result in damage to the trees. The frequency of this kind of damages was significantly smaller when using the mini-lever option

Introductory students’ attitudes and approaches to physics problem solving: major, achievement level and gender differences

Students’ attitudes and approaches to problem solving are claimed to be related to their ways they learn physics and to their success in solving physics problems. In this study, the Attitudes and Approaches to Problem Solving (AAPS) survey was used to reveal Turkish introductory university students’ attitudes and approaches to physics problem solving. The data were collected from 175 students, in the spring semester of 2015-2016 academic year, from an introductory physics course at a university in the Black See Region of Turkey. The analysis of the data was conducted by grouping the data by major, achievement level, and gender. They were no statistically significant differences between the averages of civil engineering and molecular biology majors, and between male and female students. However, we obtained a small sample correlation between students’ attitudes and exam grades that suggests high achievers’ attitudes and approaches to physics problems are more expert-like than the attitudes and approaches of low achievers. Implications for problem solving strategies and directions for further research are discussedPeer Reviewe

Fractal geometry of critical Potts clusters

Numerical simulations on the total mass, the numbers of bonds on the hull, external perimeter, singly connected bonds and gates into large fjords of the Fortuin-Kasteleyn clusters for two-dimensional q-state Potts models at criticality are presented. The data are found consistent with the recently derived corrections-to-scaling theory. However, the approach to the asymptotic region is slow, and the present range of the data does not allow a unique identification of the exact correction exponentsComment: 7 pages, 8 figures, Late

Productivity of Stump Harvesting for Fuel

The productivity of harvesting stump and root wood was studied in Norway spruce (Picea abies) stands. The objective was to create productivity models (m3/E0h) for stump wood extraction, stump wood forwarding, and site preparation, in addition to identifying work phases and improvement opportunities in the extraction and forwarding chain. Productivity models were based on time studies with professional operators. The independent variables in stump wood extraction were stump diameter (cm) and the number of stumps per hectare. For forwarding, the independent variables were volume of stump wood removed (m3/ha) and forwarding distance (m). When removing 350 stumps per ha with an average diameter of 40 cm, productivity was estimated at 7.9 m3/E0h. Increasing the number of stumps removed from 350 to 800 stumps per ha, increased productivity to 10.8 m3/E0h. Forwarding productivity was 7.8 m3/E0hwithaforwardingdistanceof250mandaload size of 7.0 m3 when removing 60 m3 of stumps per ha

Roughness and Finite Size Effect in the NYSE Stock-Price Fluctuations

We consider the roughness properties of NYSE (New York Stock Exchange) stock-price fluctuations. The statistical properties of the data are relatively homogeneous within the same day but the large jumps between different days prevent the extension of the analysis to large times. This leads to intrinsic finite size effects which alter the apparent Hurst (H) exponent. We show, by analytical methods, that finite size effects always lead to an enhancement of H. We then consider the effect of fat tails on the analysis of the roughness and show that the finite size effects are strongly enhanced by the fat tails. The non stationarity of the stock price dynamics also enhances the finite size effects which, in principle, can become important even in the asymptotic regime. We then compute the Hurst exponent for a set of stocks of the NYSE and argue that the interpretation of the value of H is highly ambiguous in view of the above results. Finally we propose an alternative determination of the roughness in terms of the fluctuations from moving averages with variable characteristic times. This permits to eliminate most of the previous problems and to characterize the roughness in useful way. In particular this approach corresponds to the automatic elimination of trends at any scale.Comment: 13 pages, 11 fugure