Volume 8, numéro 1, january 1997

EN :

The relation between the most productive scale size for particular input and output mixes and returns to scale for multiple-input multiple-output situations is explicitly developed. Data Envelopment Analysis (DEA) has been extensively applied in a range of empirical settings to identify relative inefficiencies, and provide targets for improvements. It accomplishes this by developing peer groups for each unit being operated (Decision Making Unit: DMU).

This paper introduces the technique and focuses on some of the key issues that arise in applying DEA in practice. Some illustrations of the practical applications of these results to the estimation of most productive scale sizes and returns to scale for Forest Owner's Associations (FOAs) at the local level in Japan are also provided to emphasize the advantage of this method in examining specific segments of the efficient production surface.

EN :

A farm tractor was modified to become a single-grip harvester. A forest crane was attached to the front. Time studies on 695 trees in a clear cut stand and 793 in a thinned stand indicated that productivity was similar that of Nordic specialized harvesters and of farm tractors with a rear-mounted crane. The ability to operate was good where terrain was easy and ground surface was first class. Rough terrain slowed down moving speeds considerably because of the rigid frame.

Ergonomic assessment according to a 13-point checklist appeared to be not at the same level as that of specialized Nordic forest machines, but some of the ergonomic factors could be improved rather easily and at low cost. This machine can also be used for other types of work such as cleaning verges from bushes and in conventional farming operations, which have different ergonomic demands.

The relatively low investment cost compared with that of specialized Nordic machines should contribute to reduced ownership costs.

EN :

A partly deductive time consumption model was constructed by using earlier knowledge about the importance of grapple size and pile size on the time consumption for loading shortwood. In order to estimate a complete model, only the function for the loading cycle time needs to be known.

The potential advantages of this model are an improved understanding of causal relations and the increased efficiency in producing time consumption models.

Comparison with conventionally estimated models based on large empirical studies indicated relatively good agreement, concerning both time consumption level and the influence of various loading conditions.

EN :

The static equilibrium of the Triangular Running Skyline (TRS) system was tested using a reduced scale model to see if and to what degree the carriage location and line tensions at the spars differed from the theoretically predicted ones. TRS is one of the promising environmentally sound methods for accessing the forest. The model has a span of three meters so that all conditions can be dealt with on a laboratory basis. In this test, line lengths of this model system were designed to have unstretched lengths derived from the theory of elastic catenary, to have the carriage set at a designated position. Then, the measured positions of the carriage and line tensions were compared with those derived from the theory. The results proved that the horizontal positioning error of the carriage is smaller than its vertical positioning error and that the carriage tends to be lower than its theoretical value. The greater theoretical line tension causes the error in line tension to be larger and the line tension tends to be lower than the theoretical value. In order to obtain more accurate positioning of the carriage, it is necessary to take loosening of lines, guy lines of spars, etc. into account.

EN :

The purpose of this study is to find out the effect of using the multiobjective simulation technique for logging technology and machinery optimal design. This topic was identified as important to support forest machinery designers in providing them with the necessary knowledge for carrying out the first drafts without a pilot machinery model. The method is applied to pines growing in the Russian North-West region.

EN :

The ergonomic benefits of mechanisation for the forest worker focus around the removal of the worker from the majority of the hazards and severe physical workloads inherent in the forest workplace. However, the characteristics of the current New Zealand forest industry workforce, the lack of trained operators, lack of appropriate training and selection programmes, and the high level of turnover in the New Zealand forest industry, are current obstacles to the full achievement of mechanisation's ergonomic benefits. In order for the New Zealand forest industry to maximise the economic and ergonomic benefits of mechanisation, some formal preparation of machine operators is essential.