Steaming and Heating Dipteryx panamensis Logs from Fast-Grown Plantations: Reduction of Growth Strain and Effects on Quality

Steaming and heating as pretreatments before log sawing reduce the negative effects of growth strain (GS). The object of this work was to study the reduction of GS in logs of Dipteryx panamensis from a fast-growth plantation using steaming and heating treatments and evaluate the effects on the lumber quality. According to the results, the maximum temperature in the center of the log was approximately 90°C after 24 hours for both treatments. GS decreased after heating and steaming. The average value of GS for three treatments was 2,085.61 microdeformation units (με) before the treatment, decreasing to average value to1,692.14 με after the treatments. This reduction in turn produced a reduction of crook due to sawing measured in logs and semilogs and a decrease in the values and incidence of crook, bow, twist, and split. Similarly, color parameters (L*, a*, and b*) were statistically affected by the treatment, except for parameter L* in sapwood. In general, wood darkening was observed. Lastly, both treatments applied to D. panamensis logs showed few differences in GS, in crook due to sawing measured in logs and semilogs, and in the values and incidence of crook, bow, twist, and split. Therefore, both treatments achieved GS reduction in D. panamensis lumber.

ESTIMASI HERITABILITAS DAN RESPONS SELEKSI IKAN NILA HITAM (Oreochromis niloticus) DI TAMBAK

Genetic improvement in the establishment of a rapid growth strain of Nile tilapia might be achieved through selective breeding program This research was aimed to estimate heritability and response selection of nile tilapia in brackishwater pond. Breeding activity was carried out in fresh water in hapa 2x1x1 m. Males and females were breeding in pairs with a ratio of 1: 1. The number of established families was 19 families of 50 broodstock pairs. Harvesting of larvae was done on day 14. Larvae were collected and then kept in net 2 x 2 x1 m with stocking density 125 fish/m2 for 60 days. The next stage was sexing by grouping the male and female populations in each family. Grow out was carried out in net cage (3 x 5 x1.5 m ) that were placed in brackiswater pond at salinity 25–30 g/L with density 10 fish/m2. Selection of broodstock in the male and female populations was done on weight of 250–300 g. Cut off selection was determined on weight from 316 to 382g (male) and 221–315 g (female). The results of this study showed that the estimation value for heritability of male and female were 0.42 ± 0.22 and 0.42 ± 0.23 and the estimation value for response selection were 10.66% (male) and 10.92% (female).

Beyond Shakedown-Ratcheting Boundary

The ASME Boiler and Pressure Vessel Code (Section III and Section VIII) provides requirements to avoid a ratcheting (accumulating permanent strain) condition under cyclic thermal load application. The ratchet check in this code is based on the solutions presented by Miller in 1959. One important focus in Miller’s work was to estimate the accumulated plastic strain under cyclic loading. The existing pressure vessels and piping codes have been adopting Miller’s ratchet boundary solution where there is no cyclic plastic accumulation of strain. However, some of these codes also provide limit on accumulated plastic strain under ratcheting conditions. Since the cyclic loading also causes fatigue damage in thee component, the question how to account for the interaction of ratchet deformation, which may contribute to damage in the material, and fatigue damage arises, since the fatigue curves are obtained from tests in the absence of ratcheting. This paper investigates the solutions to calculate growth strain (incremental plastic strain) and their application in design including taking into account the interaction with fatigue. Finite element analysis is presented to validate the analytical solutions.