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Due to fluctuating fossil fuel prices the use of forest biomass for energy is expected to increase considerably in the future. Today, the demand for high quality wood fuel products such as chopped firewood or pellets has increased price pressure on these products. In order to make the production more cost-effective new methods to optimize their production have to be found. Drying of raw material in the forest in order to improve the quality of the raw material and to reduce transportation costs can considerably improve the overall efficiency of the supply chain. It also enables longer storing periods and decreases GHG emissions and dry matter losses during storing. The purpose of the study was to test natural drying and the effect of different degrees of partial debarking and different methods of bark scarifying as well as covering on natural drying of energywood stems. The test included laboratory tests in Finland and field trials in Finland, Scotland and Italy, using local practices and forest species commonly used as a raw material for different forest energy products. In the laboratory test for birch, partial debarking and scarifying can be as effective drying accelerants as traditional splitting. It is important that scarifying is done all over the stem. During the test, untreated stems were drying from original 48% of moisture down to 35% during 6 months of drying between March and September. During the same period, split, partially debarked and scarified stems achieved more than 10%-units lover moisture. With pine, scarifying does not work as effectively with small percentages of removed or scarified bark.According to the results of the field trials, the debarking using a harvester head had a significant effect on moisture content decrease during the drying season especially when the stacks were covered. Covering is more vital in rainier circumstanses, but nevertheless there are also notable differences between tree species. The results show that the tested broad-leaved trees, (Petula pubescens), alder (Alnus incana) and sitka spruce (Picea sitchensis) dry faster than pine (Pinus sylvestris) and lodge pole pine (Pinus contorta).The results showed that debarking using, e.g. a harvester head, can be quite demanding due to different characteristics of tree species and diameters. The debarking device should be designed so that it could be switched on only when needed. This would ensure that the harvester head could be used to harvest normal timber and also energy wood. In conclusion, the drying season is essential to decrease the moisture content particularly in Finland and Scotland. The results show that the moisture content can be decreased by 15 20% in several months using only solar and wind power if more bark than normal is removed and the piles are covered.
Dimensional instability, more particularly its component hygroexpansivity, may cause problems in process or end-use situations in which paper or board is in contact with water or subject to changes in ambient relative humidity. Misregistration in printing, curl during copying and calender wrinkles are examples of such defects. In this paper, the in-plane hygroexpansivity of oriented laboratory sheets with different pulps and dried both freely and under restraint is studied. A linear relationship between the drying shrinkage and hygroexpansion coefficient of freely dried laboratory sheets having different fiber orientation anisotropies, was observed. Regardless of both the measurement direction (MD or CD) and the drying options (freely or restraint) all hygroexpansion coefficient values of each pulp type fell quite well on one single power curve as a function of the elastic modulus. Fiber orientation is considered via two different approaches: using fiber orientation anisotropy and using directional variable named as anisotropy index. When the anisotropy index is used, the MD and CD hygroexpansivity or the MD and CD drying shrinkage can be fit on a single curve, while the freely dried and restraint-dried sheets evidently need two different fitting curves. Between the hygroexpansion coefficient and the anisotropy index, a simple power law relationship, with two fitting parameters depending on pulp and drying restraints, is introduced.
Abstract Main research and development interest of 5G and beyond systems are focusing on solution for populated and hot spot areas, but public safety authorities need reliable communication solutions in rural and remote areas. Tactical bubbles—ad hoc-type nonpublic communications networks built with the 3rd Generation Partnership Project-based mobile technologies—offer mission critical communications services for public safety authorities in areas with bad mobile network coverage while also providing additional capacity in hot spot areas. In this experimental study, three interconnected bubbles acting on three different frequency bands—2.3 GHz (40), 2.6 GHz (7), and 3.5 GHz (n78)—are trialed. This article provides the analysis of different factors related to performance and user experience of tactical bubbles. Both ground-level and aerial trial measurements, as well as simulations, were utilized to verify our configuration for the tactical bubbles and their fulfillment of the quality requirements. The performance and coverage of the tactical bubbles are evaluated in a trial, which represents authorities’ search operations in a rural environment with hills, forests, and swamps. The achieved coverage range of the bubbles is more than 1000 m with the unmanned aerial system-based measurements, whereas by car, the coverage is less than 600 m. The effect of obstacles (ie, buildings and hills) on the coverage area and performance of bubbles is significant, especially on car-based measurements on the ground level.