The effect of cyclic twist angle on mechanical properties for AISI 1038 medium carbon steel

A group of 11 specimens AISI 1038 Medium carbon steel alloy fabricated according to ASTM standard D790-02 torsion test were twisted cyclically one in positive another to negative angle in range of angles (0o-50o), step 5 degrees for each specimen. The data from torsion test device help to get actual torques and shear stresses, later the specimens tested the tensile test to figure out the effects of cyclic angle of twist on mechanical properties for AISI 1038 Medium carbon steel. The results showed a good agreement between the theoretical and actual data (torque, shear stress) for specimens with positive angle of twist by the percentage: 98%, 91%, 96%, 93%, 91%, 89%, 88%, 85%, 82%, 81%, 80%. In other side the results for experimental tests showed a dangerous decrements in mechanical properties for cyclic or negative twist angles, the yield stress for reference specimen without twist angle is 490 Mpa, yield stress increased for angels (5o,10o,15o) by 1%, 3%, 6%, then decreased for angels (20o,25o,30o,35o,40o,45o) by 3%, 5%, 13%, 18%, 24% and 35% Respectively and the final specimen with 50o angle of twist had been broken torsional before tensile test as a result specimens groups consequent of the extrusion – intrusion defects concomitant from twisting load

Consequences de la manipulation des plants et de la variation des conditions de croissance sur le comportement d'une culture de pomme de terre, en zone mediterraneenne

In the Mediterranean area the growth vigour of seed tubers of potato can be kept at a high level by combining different storage techniques, even without or with only short cold storage. The effects of the different techniques investigated depended on the cultivar used and on the duration of the storage.Crops grown in the main season (planting in January - February) , yielded more than crops grown in the autumn season (planting in August or September). In the autumn season, soil cover reached higher values than in the main season. In the main season, however, the amounts of light intercepted and the harvest index were more favourable than in the autumn season. In both seasons, each delay of planting caused a reduction in yield, even though it increased the light-conversion efficiency and the rate of canopy development. Yields were highly correlated with the duration of the soil cover, especially for the early plantings in the main season.A late planting date during the main season was associated with a severe heat stress at the end of the growing season. In the autumn season, mainly the low temperatures and the short photoperiod were limiting the canopy development.Tubers produced during the main season had higher dry-matter contents than tubers produced during the autumn season. Autumn crops produced fewer tubers per unit area, but the size distribution was shifted towards the larger sizes.</TT

Phenology of Phlebotomus papatasi (Diptera : Psychodidae) relative to the seasonal prevalence of zoonotic cutaneous leishmaniasis in central Tunisia

International audienceThe population density of Phlebotomuspapatasi Scopoli (Diptera: Psychodidae), vector of Leishmania major Yakimoff & Schokhor (Kinetoplastida: Trypanosomatidae), the etiologic agent of zoonotic cutaneous leishmaniasis (ZCL), was assessed May-November 2005 in central Tunisia by using sticky traps. The densities of P. papatasi were found to peak in early spring and again in the autumn. The lowest densities were observed in August. Prevalence of ZCL in the governorate of Sidi Bouzid peaks in December, 3 to 3.5 mo after the fall sand fly population peak, suggesting a close temporal association with the abundance of P. papatasi