Notch Sensitivity and Defect Sensitivity under Fatigue Loading: Two Sides of the Same Medal

Notch sensitivity and defect sensitivity are two different aspects of the fatigue behavior of materials. The paper extends the Kitagawa diagram to blunt cracks (U-shaped notches) and presents the simple expression (a*/a₀)^0.5 = K_t. In such an expression a₀ is the El-Haddad's length parameter and a* is a particular blunt crack depth corresponding to the intersection between the K_th and ₀/K_t curves. The new expression provides an explicit bridging between the notch sensitivity and the sensitivity to defects.     

Presentation‐Oriented Key‐Frames Coding Based on Fractals

This paper focuses on the problem of key‐frames coding and proposes a new promising approach based on the use of fractals. The summary, made of a set of key‐frames selected from a full‐length video sequence, is coded by using a 3D fractal scheme. This allows the video presentation tool to expand the video sequence in a “natural” way by using the property of the fractals to reproduce the signal at several resolutions. This feature represents an important novelty of this work with respect to the alternative approaches, which mainly focus on the compression ratio without taking into account the presentation aspect of the video summary. In devising the coding scheme, we have taken care of the computational complexity inherent in fractal coding. Accordingly, the key‐frames are first wavelet transformed, and the fractal coding is then applied to each subband to reduce the search range. Experimental results show the effectiveness of the proposed approach.     

Network capacity assignment for multicast services using genetic algorithms

This letter focuses on the problem of network capacity assignment to accommodate the introduction of additional multicast services in existing unicast networks. The problem is firstly formalized by defining a cost function to evaluate the goodness of a given capacity allocation configuration. Then, a novel approach based on the genetic algorithms is provided to find the near-optimal solution. Experimental results are compared with those of a heuristic algorithm that provides a lower bound for the optimization problem, showing that the proposed method allows for a strong reduction of the processing time.     

Dubowitz syndrome with keloidal lesions

Spontaneous fractures of the first rib are uncommon and are usually thought to be associated with a malignant process. However, fatigue fractures of the first rib are being encountered increasingly in association with various physical activities. Typically, the fractures occur at the subclavian groove, but in the 48-year-old woman described in this report the fracture was unexpectedly situated in the posterior portion of the rib and was the result of snow shovelling, which was a new activity for the patient.     

STRESS DISTRIBUTIONS FOR V-SHAPED NOTCHES UNDER TENSILE AND BENDING LOADS

Abstract— An analytical solution has been proposed recently by the authors to describe, with a unified approach, the stress fields in the neighbourhood of sharp cracks, V-shaped notches and re-entrant corners in plates subjected to remote tensile loading. In the present paper, the above solution is revised and extended, by also determining the relevant displacement fields and the degree of accuracy of the solution for both the longitudinal and transverse stress fields. Afterwards, since the stress field depends on the type of loading, the circumferential principal stress component is modified to account for bending in fatigue life predictions, while the radial principal stress is almost negligible in this case. The analytical results are compared with finite element values obtained for different geometries loaded under tensile or bending conditions, as well as with other closed-form solutions. The new expressions seem to give better stress estimates than the currently available approximate solutions, whether analytical or numerical, when the opening angle of the re-entrant corner is equal to or greater than π/2. Hence they should represent a good starting point to describe stress distributions induced by stress raisers with large and well defined opening angles such as shafts with shoulder fillets, gears and weldments.     

Short communication: In vitro rumen gas production and starch degradation of starch-based feeds depend on mean particle size

Our objective was to model the effect of mean particle size (mPS) on in vitro rumen starch degradation (IVSD) and the kinetics of gas production for different starch-based feeds. For each feed, 2 batches of the same grains were separately processed through 2 different mills (cutter or rotor speed mills), with or without different screens to achieve a wide range of mPS (0.32 to 3.31 mm for corn meals; 0.19 to 2.81 mm for barley meals; 0.16 to 2.13 mm for wheat meals; 0.28 to 2.32 mm for oat meals; 0.21 to 2.36 mm for rye meals; 0.40 to 1.79 for sorghum meals; 0.26 to 4.71 mm for pea meals; and 0.25 to 4.53 mm for faba meals). The IVSD data and gas production kinetics, obtained by fitting to a single-pool exponential model, were analyzed using a completely randomized design, in which the main tested effect was mPS (n = 6 for all tested meals, except n = 7 for corn meals and n = 5 for sorghum meals). Rumen inocula were collected from 2 fistulated Holstein dairy cows that were fed a total mixed ration consisting of 16.2% crude protein, 28.5% starch, and 35.0% neutral detergent fiber on a dry matter basis. The IVSD, evaluated after 7 h of rumen incubation, decreased linearly with increasing mPS for corn, barley, wheat, rye, pea, and faba meals, and decreased quadratically with increasing mPS for the other meals. The y-axis intercept for 7-h IVSD was below 90% starch for corn, barley, and rye feeds and greater than 90% for the other tested feeds. The mPS adjustment factors for the rate of rumen starch degradation varied widely among the different tested feeds. We found a linear decrease in starch degradation with increasing mPS for barley, wheat, rye, and pea meals, whereas we noted a quadratic decrease in starch degradation for the other tested meals. Further, we observed a linear decrease in the rate of gas production with increasing mPS in each tested feed, except for pea meal, which had a quadratic relationship. For each 1 mm increase in mPS, the gas production was adjusted by ?0.009 h^?1 for corn, ?0.011 h^?1 for barley, ?0.008 h^?1 for wheat, and ?0.006 h^?1 for faba, whereas numerically greater adjustments were needed for oat (?0.022 h^?1), rye (?0.017 h^?1), and sorghum (?0.014 h^?1). These mPS adjustment factors could be used to modify the starch-based feed energy values as a function of mean particle size, although in vivo validation is required.     

Effect of spot weld distribution characteristics on the fatigue strength of resistance welded joints

Abstract

Resistance spot-welded joints are often the Achilles heel of structures subject to fatigue stresses. Although many papers, applying both numerical and experimental techniques, have been published in the last few years, the problem of correlation between joint design and fatigue strength has not yet been satisfactorily resolved.

The aim of this article is to identify such a correlation for simple lap joints, to provide designers with a useful tool allowing them to evaluate easily and quickly the improved fatigue strength obtainable by changing the number of weld spots.     

Fatigue design of complex welded structures

This paper is concerned with the design of complex welded structures subjected to fatigue loadings. In the last years it has been developed a new approach for predicting the high cycle fatigue behaviour of welded joints, based on the Notch-Stress Intensity Factors of the uncracked geometries, which have been successfully applied to welded joints of different geometries using an analytical frame in combination with stress data obtained from Finite Element Analyses. The approach is based on the observation that the very small weld toe radius obtained by using traditional welding technologies is consistent with the assumption of a sharp V-notch geometry, characterised by an exponential stress field, which the fatigue strength depends on. Recently published Eurocodes suggest the use of a hot spot approach, both for steel and aluminium structures. Nevertheless the evaluation of fatigue strength of engineering complex structures remains a difficult and, in some way, controversial subject. We hope that this synthetic presentation of the N-SIF and hot spot approaches as compared to the European Standards could help to clarify the subject and to design better and more reliable structures.     

Metabolic and hormonal control of energy utilization and partitioning from early to mid lactation in Sarda ewes and Saanen goats

In a recent study, we observed that starch-rich diets used in mid lactation induced lower milk production persistency and higher body fat accumulation in dairy ewes compared with dairy goats. Because these species differences could be linked to hormonal mechanisms that drive energy partitioning, in the same experiment, we explored the evolution of metabolic and hormonal status during lactation to test this hypothesis. Twenty mature Sarda dairy ewes and 20 mature Saanen goats [15–134 ± 11 d in milk (DIM), mean ± SD] were compared simultaneously. In early lactation, each species was allocated to one dietary treatment: high-starch diet [HS: 20.4% starch, on dry matter (DM) basis], whereas from 92 ± 11 DIM, each species was allocated to 1 of 2 dietary treatments: HS (20.0% starch, on DM basis) and low-starch (LS: 7.8% starch, on DM basis) diets. Blood samples were collected in the morning to analyze glucose, nonesterified fatty acids (NEFA), growth hormone (GH), insulin, and insulin-like growth factor I (IGF-I). Data were analyzed using the PROC MIXED procedure of SAS with repeated measurements (SAS Version 9.0). The HS and LS diets applied in mid lactation did not affect metabolic status of the animal within species; thus, only a comparison between species was carried out. From early to mid lactation, plasma glucose concentration was higher in ewes than in goats (54.57 vs. 48.35 ± 1.18 mg/dL), whereas plasma NEFA concentration was greater in goats than in ewes (0.31 vs. 0.25 ± 0.03 mmol/L). Goats had higher plasma GH concentration and lower plasma insulin content than ewes (4.78 vs. 1.31 ng/mL ± 0.47; 0.11 vs. 0.26 μg/L ± 0.02). Plasma IGF-I concentration did not vary between species. The comparison of metabolic and hormonal status of lactating Sarda dairy ewes and Saanen goats, carried out by studying simultaneously the 2 species in the same stage of lactation and experimental conditions, suggests that the higher insulin and glucose concentration observed in Sarda ewes explains why they partitioned more energy toward body reserves than to the mammary gland, especially in mid lactation. This can justify the negative effect of high-starch diets in mid-lactating Sarda ewes. Conversely, the highest GH and NEFA concentration observed in Saanen goats explain why they partitioned more energy of starch diets toward the mammary gland than to body reserves and justify the positive effect of high-starch diet in mid lactation. Together, these different responses contribute to explain why specialized dairy goats, such as the Saanen breed, have a higher milk production persistency than specialized dairy sheep breeds, such as the Sarda.     

Participation of tachykinins in experimental models of lung damage

In the present investigation a possible involvement of tachykinins during sulfur dioxide-(SO2) and metabisulfite-(MBS) induced bronchoconstriction, and paraquat (PQ)-induced mortality was studied. SO2 (250ppm) inhalation and MBS (3mM) perfusion induced a marked decrease of compliance and conductance in the isolated and perfused lung. SO2-induced bronchoconstriction was associated with release of Calcitonin Gene Related Peptide, suggesting activation of capsaicin sensitive sensory nerves. Pretreatment of animals with capsaicin, in order to deplete the tachykinin content of sensory nerves, significantly reduced SO2- and MBS-induced bronchoconstriction. PQ (25mg/Kg) treatment induced high mortality (75%) after 3 weeks. Pretreatment with capsaicin significantly protected versus PQ induced mortality (25%). The results suggest that tachykinin content in the respiratory airways participate to SO2- and MBS-induced bronchoconstriction and PQ mortality.