Search

AkuLite Report 8

AkuLite Report 8

AkuLite Report 8

Ej belagd 231017

Different methods for shelterwood cutting have been used in differ-ent parts of Europe since the middle ages. The use of shelter wood cutting in Norway spruce (Picea abies (L.) Karst.) forests in Sweden met a revival in the early 1990s as an alternative for the dominating clear-cutting system when silvicultural costs increased dramatically for the latter. Shelterwood cutting systems involve some possible problems but also a lot of positive effects. Among the problems are increased risk of wind throw and damage of the remaining shelter trees caused by the cutting operation. Positive effects are for example a valuable growth in the remaining trees and increased biological di-versity. This study is based on a total of 79 trees from 4 different treatments in a spruce shelterwood, cut in 1994, in the middle of Sweden (62,4º N). The treatments were the following; 2 shelterwood cuttings leav-ing a stand of 250 stems/ha with dominant trees respective co-dominant trees, 2 shelter wood cuttings leaving a stand of 400 stems/ha with dominant trees respective co dominant trees. From each tree 2 increment cores were taken at breast height and the an-nual year ring growth from 1984 to 2001 was calculated. The study compared the difference in growth response between dominant and co dominant trees. The response in growth caused by the release came earlier in the dominant trees than in the co-dominant. The level of reaction, measured as increase in basal area at breast height, was higher in the co dominant trees than in the dominant, after eight years 44% and 39% (co-dominant, 400 respective 250 stems/ha) respective 20% and 27% (dominant, 400 respective 250 stems/ha). There was also a difference in response between trees of different diameters. A tree that had a small diameter in 1994 when the shelter-wood cut was performed had a higher rate of reaction than thicker trees. This was evident in all treatments. The remaining shelter trees reacted to the liberating shelter cut in a good, Olika system för skärmskogsbruk har använts i Centraleuropa sedan medeltiden. När skogsvårdskostnaderna i det dominerande kalhyggesbruket under början av 1990-talet steg kraftigt fick metoden ett uppsving i det svenska skogsbruket. Det var främst på bördiga marker med gran (Picea abies (L.) Karst.) som metoden kom att användas. Att använda sig av skärmskogsbruk har vissa risker men även fördelar. Bland riskerna finns en ökad risk för vindfällning och risk för ökade skador i samband med drivningsarbetet. De fördelar som finns är bl.a. en värdefull tillväxt på de kvarvarande skärmträden och ökad biologisk mångfald. Denna studie baseras på totalt 79 träd från 4 olika behandlingar i ett bestånd med skärmställd gran i mellersta Sverige. Skärmen ställdes under 1994. De fyra olika behandlingarna var följande: två skärmar med 250 stammar/ha, den ena med härskande och den andra med medhärskande träd, samt två skärmar med 400 stammar/ha, en med härskande och en med medhärskande träd. Från varje träd togs två borrkärnor och årsringarnas tillväxt beräknades för åren 1984 till 2001. Studien har jämfört tillväxtreaktionerna i härskande och medhärskande skärmträd. Tillväxtreaktionen efter den friställning som skärmhuggningen innebär kom något tidigare i härskande träd än i medhärskande. Nivån på tillväxten, mätt som relativ ökning av grundytan var högre i de medhärskande än i de härskande träden, efter åtta år 44 % och 39 % respektive 20 % och 27 %. Det finns även en skillnad i tillväxtreaktion mellan träd med olika diameter. Ett träd med liten diameter 1994 när skärmhuggningen genomfördes har haft en högre procentuell tillväxt än ett grövre träd. Detta mönster finns i samtliga behandlingar. Effekten avtar med ökad diameter. De träd som har lämnats som skärmträd reagerar med bra tillväxt trots sin höga ålder. Ett träd som var medhärskande vid ingreppet 1994 var inte det på grund av dålig tillväxtförmåga utan snarare därför att det var utsatt för hårt konkurrenstryck från omkringli

Purpose: To establish the sufficiency of the ocular accommodation and to characterize accommodative problems and related symptoms among otherwise healthy young school children. Subjects and Methods: Children from a junior level school were invited to participate in an examination of the accommodative function which was then compared to expected age levels. The amplitude of accommodation was examined using Donders’ push-up method. A questionnaire containing four different questions linked to four different subjective symptoms (headache, asthenopia, floating text, facility problems) was also used. Results: The results showed lower amplitudes than expected in a large group of children and not equivalent to the expected age values. More than one third of the children reported subjective symptoms at near. The incidence of subjective symptoms emerged at the age of 7.5 years and there was significant relationship between low amplitude and subjective symptoms. Conclusions: Accommodation is not as sufficient in young children as expected. Subjective symptoms emerge at the age of 7.5 years and there is a clear relation between accommodative parameters and these subjective symptoms. Clear standards for diagnosing an accommodative dysfunction need to be further refined Because accommodative dysfunctions may result in subjective symptoms, it is of great importance to identify this dysfunction to prevent unnecessary near vision problems.

A method for recognizing inhalations in spontaneous speech is presented. It is similar to the template matching technique; a distance measure is calculated between a reference sound and an equally long portion of the same sound being tracked. A feature representation consisting of the standard Mel Frequency Cepstral Coefficients (MFCC), obtained by performing a discrete Cosine Transform of the mel-scaled filterbank spectrum is used. MFCC's are calculated every 5 ms. The comparison is then done by computing the euclidian distance between the cepstral coefficients of each frame of the two sounds. A low distance value means that the two compared inhalations are likely to be similar. The method can detect inhalations in both male and female spontaneous speech. The method is most suited for signals with low noise and high average intensity (studio recording) but can also be used on noisier recordings with lower average intensity, albeit with poorer results.