A general model of the equations of generalized thermo-microstretch for an infinite space weakened by a finite linear opening mode-I crack is solved. Considered material is the homogeneous isotropic elastic half space. The crack is subjected to a prescribed temperature and stress distribution. The formulation is applied to generalized thermoelasticity theories, using mathematical analysis with the purview of the Lord-Şhulman (involving one relaxation time) and Green-Lindsay (includes two relaxation times) theories with respect to the classical dynamical coupled theory (CD). The harmonic wave method has been used to obtain the exact expression for normal displacement, normal stress force, coupled stresses, microstress and temperature distribution. Variations of the considered fields with the horizontal distance are explained graphically. A comparison is also made between the three theories and for different depths for the case of copper crystal.
Maritime transport is facing a set of technical challenges due to implementation of ecological criterions on 1st Jan. 2020 and 2021 by the International Maritime Organization. The advantageous properties of natural gas (NG) as fuel in conjunction with dual-fuel (DF) internal combustion engines (ICE) potentially enables the fulfilment of all criterions. Moreover the 2020 global sulfur cap in combination with its low content in NG potentially enables to recover higher rates of waste heat and exergy of exhaust gas without the risk of low temperature corrosion. In this study the influence of sulfur content in NG and pilot fuel oil (PFO) on the sulfuric acid condensation temperature was investigated in order to determine the rate of waste heat (quantity) and exergy (quality) of four-stroke DF IC engine’s exhaust for 50%, 85% and 100% of engine load. Determined parameters were compared with two sets of reference values calculated for the same engine: a) fueled with NG and PFO with fixed minimum exhaust temperature set as 423.15 K, b) fueled with 3.5% sulfur mass fraction fuel oil only with variable minimum exhaust gas temperature. The results show that the assumption of case a) can lead to significant reduction of recovered rates of exhaust waste heat and exergy in the ranges of 10% to 24% and 43% to 57%, respectively. Higher values were obtained for case b) where the ranges of unrecovered rate of heat and exergy achieved 20% to 38% and 60% to 70%.
Changes in body mass and body reserves of Little Auks (Alle alle) were studied throughout the breeding season. Body mass loss after chick hatching was analyzed with respect to two hypotheses: (1) mass loss reflects the stress of reproduction, (2) mass loss is adaptive by reducing power consumption during flight. Body mass of both males and females increased during incubation, dropped abruptly after hatching, and remained stable until the end of the chick-rearing period. These changes were largely due to change in mass of fat reserves. Body mass, fat, and protein reserves, when corrected for body size, did not differ between sexes at the end of incubation. Female size-corrected body mass at that time was correlated with peak body mass of chicks. The estimated energy savings for flight due to the decline in adult body mass after chick hatching were small compared with the total energy expenditure of adults feedings chicks, which did not support hypothesis (2). The contribution to chick feeding was not equal; the ratio of females to males caught with food for chicks was 1.8. Size-corrected body mass during chick-rearing was lower in females, proportional to their higher chick feeding effort compared with males. Females, in contrast to males, lost protein reserves during chick-rearing. Digestive tract mass of adults increased by half throughout the breeding period. These findings supported elements of hypothesis (1). Despite high energy expenditure rates, both sexes had about 10 g of fat reserves at the end of chick feeding. Body mass of both sexes was constant during the greater part of the chick-feeding period. It was suggested therefore that mass loss is regulated with respect to lower fat reserves required during chick-rearing.