Deltagerdriven forskning – växtodlingsgruppen: Resultat och utvärdering av arbetet under 1998 till 2001

De ekologiska lantbrukarna i Sverige har under lång tid utfört olika typer av utvecklingsarbete på gårdsnivå (Wivstad, 1999). I den fortsatta utvecklingen av ekologiskt lantbruk är det viktigt att ta tillvara dessa erfarenheter och kunskaper. Deltagardriven forskning är en förändringsprocess (Ullmark, 1998) där aktiva lantbrukare, rådgivare och forskare arbetar i grupp utifrån gemensamma intresseområden. Syftet är att knyta ihop forskarnas, rådgivarnas och lantbrukarnas teoretiska och praktiska kunskaper och erfarenheter. Alla som medverkar i processen är lika viktiga och alla parter som berörs av resultaten har möjlighet att påverka gruppens arbete och utveckling (Ullmark, 1998). Tillsammans identifierar gruppen problem och använder/utvecklar för lantbrukaren relevanta försöks- och forskningsmetoder som kan bidra till att lösa de praktiska problem som lantbrukaren faktiskt ställs inför. Genom deltagardriven forskning kan lantbrukarna även få möjlighet till att påverka var och hur forskning bedrivs. Forskningsfrågorna kan hämtas från lantbrukssystemets olika delar samt göra gruppen medveten om hur olika delar påverkar helheten (Wivstad, 1999; Eksvärd et al, 2001). I förlängningen kan deltagarna bli informatörer och överföra idéer till andra lantbrukare (Ullmark, 1998). Centrum för uthålligt lantbruk, CUL, placerat vid SLU, har sedan 1998 ansvarat för det tvärvetenskapliga projektet ”Deltagardriven forskning” som ett verktyg för regional utveckling av det ekologiska lantbruket. Det övergripande målet har varit att öka kunskapen om hur man kan åstadkomma uthålliga lantbrukssystem. Projektet startade med sex delgrupper inriktade på följande områden: grönsaker – friland, grönsaker – växthus, höns, växtodling, biogas samt grisproduktion. Därefter har några tillkommit och några avslutats. För aktuell information se hemsidan: www.cul.slu.se. Ytterligare beskrivning kan fås i ”Deltagardriven forskning – forskningsinriktad aktörssamverkan för svenskt lantbruk” (Eksvärd, i tryck)

Human Hantavirus Infections, Sweden

The prevalent human hantavirus disease in Sweden is nephropathia epidemica, which is caused by Puumala virus and shed by infected bank voles (Clethrionomys glareolus). To evaluate temporal and spatial patterns of this disease, we studied 2,468 reported cases from a highly disease-endemic region in northern Sweden. We found that, in particular, middle-aged men living in rural dwellings near coastal areas were overrepresented. The case-patients were most often infected in late autumn, when engaged in activities near or within manmade rodent refuges. Of 862 case-patients confident about the site of virus exposure, 50% were concentrated within 5% of the study area. The incidence of nephropathia epidemica was significantly correlated with bank vole numbers within monitored rodent populations in part of the region. Understanding this relationship may help forestall future human hantavirus outbreaks

FÖR HJÄRTAT OCH SNILLET - om Kungl. Samhällets emblem

Emblem och sigill har förekommit i Kungl. Samhället från dess tillblivelse på 1770-talet. Minnespenningar och minnesmedaljer var ofta förekommande under akademiens tidigare år för att därefter bli alltmer ovanliga. Under de senaste årtiondena har emblem åter kommit i mer omfattande bruk, i samklang med det övriga samhällets tilltagande intresse av emblem och logotyper. I uppsatsen med tyngdpunkten på de senaste 25 åren beskrivs Kungl. Samhällets emblem, minnesmedalj, ledamotnål och ordförandekedja. De språkvarianter som här förekommer är svenska, latin och runor, men märkligt nog inte engelska

Influence of shot peening on fatigue durability of normalized steel subjected to variable amplitude loading

The influence of shot peening on the fatigue durability of normalized carbon steels subjected to variable amplitude loading has been investigated. The relaxation of residual stresses was recorded during the fatigue life time. Strain amplitude spectra were extracted from real spectra recorded from components in service. The results were compared with data achieved from constant amplitude testing. In both types of tests parallel studies were made on both peened and unpeened specimens. Shot peening leads to pronounced increase in life time, especially for smaller amplitudes. For both variable and constant amplitude loading shot peened specimens exhibit longer life provided the residual stresses during fatigue loading do not relax more than to about 60% of their initial value. To get an improvement in life time of at least a factor two for peened specimens, the stress amplitude in constant amplitude loading or the maximum stress amplitude in variable amplitude history must not be more than 20% larger than the magnitude of the initial residual stresses. This limit corresponds to 1.2 times the yield strength of the unaffected material

Temperature and strain rate dependence of the dynamic strain ageing effect in an Al-Zn-Mg alloy

An AA7030 alloy (Al-5\ub74Zn-1\ub72Mg) was tested for evidence of dynamic strain aging in naturally aged and peak aged condition and under varying conditions in terms of strain rate and temperature. Clear evidence in terms of strain rate sensitivity, serrated yielding (Portevin-Le Chatelier effect) and propagative plastic instabilities was observed in the naturally aged temper while the peak aged temper only showed serrated yielding. Further evidence of dynamic strain aging was the temperature and strain dependence of the strain rate sensitivity, which can be explained by the additional dislocation activation energy resulting from solute pinning. Investigation of the specimen surfaces was carried out to reveal an orange peel structure with pronounced glide bands. Small cracks within individual grains rather than grain boundary cracking could be observed. \ua9 2006 Institute of Materials, Minerals and Mining

Influence of overloading on fatigue durability and stability of the residual stresses in shot peened normalized steel

The present investigation deals with the effect of overloads on the stress relaxation and fatigue life time of shot-peened near-pearlitic steels. Single cycles with a total strain amplitude of 0.6 % with start in tension or compression were exerted either at the very beginning or after 1000 cycles and superimposed on the constant total strain amplitude test at 0.3 %. The results were compared with the constant amplitude test data. It was shown that such overloading can reduce the fatigue life time by 25%-60% of the life time obtained in constant amplitude tests. Maximum amount of reduction was obtained in overloading histories started with straining in tension. The stress amplitudes and corresponding mean stress development after overloading were also recorded and used to interpret the effects of overloads on the fatigue life times. In addition the residual stress relaxation throughout the whole lifetime was followed

Development of the unloading stiffness during cyclic plastic deformation of a high-strength aluminium alloy in different tempers

The development of stiffness during unloading from peak stress during cyclic plastic deformation (low cycle fatigue) was studied in a high-strength Al-5.4Zn-1.2Mg alloy, both in naturally aged and peak aged conditions. A phenomenological model based on a 2nd order stress–strain relationship was developed using data from detailed recordings of the stress-strain hysteresis loops. Three stages of the parameter values were identified: an initial transition part of the fatigue life time, a major stationary stage shifting over to the final stage where failure modes become prominent. The nonlinear stiffness was found to be asymmetric with respect to tension and compression. Further, the naturally aged material generally shows larger stiffness for both positive and negative stresses than does the peak aged material. Finally, the stiffness for the naturally aged condition exhibits larger scatter compared to the peak aged materials, interpreted as inferior averaging in the dislocation structures

Effect of heat treatment on the strain hardening behaviour of an Al-Zn-Mg alloy

The strain hardening of the Al-5.2Zn-1.2Mg alloy AA7030 in different conditions has been investigated. The dislocation related strengthening was described by the Voce equation and the quantitative effects of different superposition laws have been studied. All tempers, except the over-aged, suffer from plastic instability before the geometric Consid\ue8re condition is reached. This was attributed primarily to the occurrence of shear failure due to dynamic strain ageing effects. For plastic strain levels below approximately 8 %, preceding the plastic instability, the results show that the saturation stress in the under and peak-aged tempers is independent of heat treatment, whereas the kinetics of structure formation differs. Using a linear superposition law in the under and peak aged tempers has negligible effects, whereas the use of Pythagorean addition for the over-aged temper significantly decreases the goodness-of-fit, although not to unacceptable levels. Furthermore, the naturally aged temper shows strong influence of dynamic precipitation