Modeling the effect of length on yield of sawn timber grades in Norway spruce (Picea abies (L.) Karst.)

The aim of the study was to model and analyse the effect of length on grade yield of timber from different stem parts in Picea abies, and to use the models to simulate the cost of reduced grade yield due to increased length. The boards were simulated having lengths ranging from 20 to 60 dm starting at stump level, 4 m above stump level and 8 m above stump level, respectively. Logistic regression models showed that length had a significant effect on grade yield, and this length effect was stronger in strength grading according to INSTA 142 (IN) compared to appearance grading according to Nordic Timber (NT). The length effect was most pronounced in butt logs, and somewhat greater in middle logs compared to top logs. Also a smaller length effect in inner boards compared to boards farther from the pith was found for IN-grading. The cost of the decrease in grade yield with increasing length will depend on the assumptions about the price gap between the grades. Current market prices in both grading rules gave a decrease in value of the sawn timber in stock by about 6% with an increase in the log length from 45 to 60 dm. In addition, a decrease in yield of timber in longer logs will amplify this effect, while a higher efficiency in the production process will diminish it.     

SnO2-Based Gas (Methane) Anodes for Electrowinning of Aluminum

SnO₂-based and carbon-based gas anodes were studied in molten Na₃AlF₆-AlF₃-Al₂O₃ at 1123 K (850 °C) for aluminum electrolysis. Methane was introduced to the porous anodes to take part in a three-phase (anode/electrolyte/methane) boundary reaction. Carbon was used as the cathode. It was observed that the anode potential was reduced by 0.6 V and that the current was increased up to three times in galvanostatic and potentiostatic tests after the introduction of methane on SnO₂-based anodes. A measurable depolarization effect and lower consumption of carbon after the introduction of methane on carbon anodes were also demonstrated.     

Plasma etching of different polydimethylsiloxane elastomers, effects from process parameters and elastomer composition

Plasma etching of three different polydimethylsiloxane elastomers has been studied. One elastomer was a commercially available kit (Sylgard-184) and the other two were made by mixing individual components. The etching was done in a multi-wafer tool. The process gas used in the etching was a mixture of SF₆ and O₂. The etch rate was measured as a function of pressure for all three materials at the centre and the edge of the etched structures. It was found that fillers in the elastomer reduces the etch rate but has little effect on the shape of the etched surface. Second, it was found that excess of chain ends in the elastomer gives larger changes in the shape of the etched surface, as pressure changes. Third, it was found that loading (reduction of etch rate) is significant in the presence of dummy silicon wafers compared to glass wafers.     

A Compact 3V, 70mW, 12-bit Video-Speed CMOS ADC

A 12-bit video speed pipelined switched capacitor analog-to-digitalconverter (ADC) has been implemented in a 0.5 µmstandard CMOS process. It operates from a single 2.6–;3.3Vsupply, dissipates 23mA (independent of supply voltage) at 20MSPS and occupies only 1.1mm ². A 61dB SINAD (f_in = 4.5 MHz) and an effective resolution bandwidthof 9 MHz is achieved.     

Effects of different dietary fat levels in cage‐fed Atlantic mackerel (Scomber scombrus)

In wild Atlantic mackerel, Scomber scombrus, the lipid content of the lateral muscle varies according to the season from around 30% in autumn to less than 5% in spring. To be able to offer mackerel with optimal quality on the market during spring or early summer after overwintering, it is necessary that the muscle lipid content is close to 30%, which is favoured by the customers. Wild caught mackerel were kept in salmon cages fed a high energy (300 g fat kg^{– 1} ) salmon diet rich in n‐3 polyunsaturated fatty acids from October 1997 to April 1998. Fish were submerged at 20—40 m at a temperature above 5 °C from January until April. Then the fish were brought to the surface and randomly divided into three duplicate groups, i.e., non‐fed, 150 g fat kg ^{– 1}, and 300 g fat kg ^{– 1} and kept until August 1998. The mortality was very low and the body weight doubled concomitant with an increased muscle lipid content from 19.5% to 30.9% during the first six months. Both groups receiving feed further increased the body weight and muscle lipid content at the same magnitude towards the end of the experiment. During the first six months the cross sectional area (CSA) of red muscle fibres increased 3.3fold and this size was maintained throughout the experiment. In contrast, in non‐fed mackerel the increase in CSA of red muscle fibres was 1.5fold. White muscle fibres revealed a much weaker response in fed mackerel and were not affected in mackerel deprived of feed. In wild mackerel the fatty acid oxidation (β‐oxidation) capacity dominated in the red part of the lateral muscle. During the winter an increased β‐oxidation capacity was found in heart and liver, whereas both red and white part of the lateral muscle showed a low fatty acid catabolism. In contrast, during summer red and white part of the lateral muscle possessed high β‐oxidation capacities, particularly in high energy‐fed and non‐fed mackerel. It is concluded that it is possible to feed captive mackerel during the winter and produce mackerel with a high quality for the market in early spring.     

Status,plans and technologies for offshore wind turbines in Europe and North America

The worldwide demand for renewable energy is increasing rapidly because of the climate problem, and also because oil resources are limited. Wind energy appears as a clean and good solution to cope with a great part of this energy demand. In Denmark for example, 20% of the electricity is produced from wind, and plans are towards reaching 50%. As space is becoming scarce for the installation of onshore wind turbines, offshore wind energy, when possible, seems as a good alternative. This work describes, for Europe and North America, the potential for offshore wind energy, the current status of this technology, and existing plans for the development of offshore wind parks. It also presents existing as well as promising new solutions for offshore wind energy.     

The design of survivable directed networks

We study a survivable network design problem:the directed network design problem with connectivity constraints (DNCC). Some applications in telecommunications are presented. We discuss two integer linear programming models for DNCC, and relate these. The main body of the paper is a study of DNCC from a polyhedral point of view. We give several classes of nonredundant inequalities for polytopes associated with the problem. A cutting plane algorithm based on the polyhedral results is described and some computational results are given.     

The influence of storage and drying methods for Scots pine raw material on mechanical pellet properties and production parameters

Converting solid biomass into pellets through densification greatly improves logistical handling and combustion processes. Raw material properties can affect pellet quality. This study investigated how storage and drying methods for wood (Pinus sylvestris L.) used as a raw material for pellet production influenced pellet durability, bulk density and energy consumption. The pelletization experiments were performed using a Sprout Matador M30 press (nominal production capacity 3.5 tonnes/h). Results showed that pelletization of 11 months stored wood compared to fresh material and high drying temperature (450 °C) compared to 75 °C resulted in higher energy consumption, probably due to increased friction in the matrix caused by the loss of extractives. However, the pellets produced were of higher density than those made from fresh material dried at a low temperature. The latter had the highest durability. Increased energy consumption showed no correlation with pellet durability.