Comparison of M. longissimus dorsi pigment concentration from implanted and control Angus and Limousin bulls and steers

M. longissimus dorsi total pigment concentration, visual color score and 24-h pH values were evaluated in a 2(3) factorial design that included bulls versus steers, Zeranol implants versus control and Angus versus Limousin comparisons. Bulls had greater total pigment concentration than steers (3.25 versus 2·90 mg/g; P < 0·01) and darker colored lean (P < 0·01). Twenty-four hour pH values did not differ between bulls and steers. Zeranol implanting and breed had no effect on total pigment concentration or visual color score; however, Limousin had higher (P < 0·05) 24-h pH values than Angus. The initial slaughter group (N = 10; average age = 256 days) had 34% less total pigment than the final slaughter group (N = 48; average age = 458 days). The correlation between visual color score and total pigment concentration was -0·65. These results indicate that the darker colored lean from bulls is due in part to an increase in pigment concentration.     

Experimental results of the erosion of molybdenum due to blistering by He+ bombardment

We report some preliminary measurement of the erosion rate of plasma dumps when bombarded with 100 keV He⁺ ions at high power density ( 1 MW/m²). The expected erosion rates, based on measurements of He blistering that were made at lower power density ( 0.3 MW/m²), indicate a potentially serious problem for fusion reactors. Our tests use a reactorlike power density and produce He blisters at a rate that is slower than predicted by 2 to 4 orders of magnitude, depending on the temperature of the molybdenum target.     

Determinants of off-road vehicle transmission 'shift quality'

This study was conducted to determine the relationship between factors associated with a tractor transmission shift and the tractor operator's judgement of the quality of the shift. The specific objective was to measure experienced tractor operators' ratings of shift 'acceptability' as peak acceleration, peak jerk and direction of initial acceleration were varied at two levels of background vibration. A six-degree-of-freedom vehicle motion simulator in the Deere & Company Technical Center's human factors laboratory was used to simulate the background vibration and to control the experimental variables. The key results are: (1) The most important factor influencing 'shift quality' is the peak acceleration experienced during the shift. (2) Background vehicle vibration experienced by the tractor operator affects his perception of 'shift quality'. Higher background vibration masks the acceleration experienced during a shift and makes the shift more acceptable than when experienced at a low level of background vibration. (3) Peak jerk experienced during a shift has a negligible effect on 'shift quality'. (4) Upshifts and downshifts of the same peak acceleration, peak jerk, and background vibration receive the same general rating of 'shift quality'.     

The behavior of small fatigue cracks at notches in corrosive environments

The behavior of small cracks growing out of the roots of blunt notches in compact type specimens of an austenitic steel was characterized under fatigue loading in wet H ₂ plus air environment. The growth rates of cracks in the size range of 0.125 mm to 0.75 mm were up to two orders of magnitude higher than the rates expected for conventional cracks at equal stress intensity range, K. It was also observed that the small cracks grew at these fast rates only in corrosive environments when the loading frequency was 0.02 Hz or less. At a frequency of 10 Hz, the behavior was in agreement with the trend predicted for conventional size cracks.The above observations are rationalized in terms of the breakdown of the concept of a single parameter representation of the crack tip stress and strain field by K or in terms of differences in crack tip environments between small and long cracks for the same bulk environment. A simple engineering model is proposed which adequately represents the observed small crack growth behavior.

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Résumé On a procédé à la caractérisation, sous charges de fatigue en atmosphère humide de H ₂ et d'air, de petites fissures se développant à partir des racines d'entailles arrondies dans des éprouvettes compactes.Les vitesses de croissance des fissures d'une taille allant de 0,125 à 0,750 mm se sont révélé être de deux ordres de grandeur plus grandes que les vitesses prévues dans le cas de fissures conventionnelle, soumises aux mêmes variations de l'intensité de contrainte K. On a également observé que de petites fissures croissaient à ces grandes vitesses seulement dans des atmosphères corrosives, lorsque la fréquence de sollicitation était de 0,02 Hz ou moins. A la fréquence de 10 Hz, le comportement observé s'est trouvé en accord avec les tendances prévues pour des fissures de taille conventionnelle.Les observations ci-dessus sont rationnalisées en un élargissement du concept de représentation monoparamétrique par le facteur K du champ de contraintes et de dilatation à l'extrémité de la fissure, ou en termes des différences rencontrées dans l'environnement local de l'extrémité d'une fissure, selon que celle-ci est longue ou courte, et ce dans un même environnement global.On propose un modèle simple utilisable en pratique, pour représenter de manière adéquate le comportement à la croissance observé pour des petites fissures.

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Metallurgy Department     

Recognition of moving objects using feature signatures

An important application of machine vision systems is the recognition of known three-dimensional objects. A major difficulty arises when two or more objects project the same or similar two-dimensional image, often resulting in misclassification and degradation of system performance. The changes in images which result from the motion of objects provide a source of three-dimensional information which can greatly aid the classification process, but this three-dimensional analysis is computationally complex and subject to many sources of error. This work develops a methodology which utilizes the information derived from the apparent changes in object features over time to facilitate the recognition task, without the need to actually recover the three-dimensional structure of the objects under view. The basic approach is to generate a ``feature signature' by combining the feature measurements of the individual regions in a long sequence of images. The static information in the individual frames is analyzed along with the temporal information from the entire sequence. These techniques are particularly applicable in situations where static image processing methods cannot discriminate between ambiguous objects. Two example implementations are presented to illustrate the application of the techniques of object recognition using motion information.     

Carbonitriding at 700°C with subsequent hardening of the surface layer

Conclusion Carbonitriding at 700°C in a mixture of 70–30% of ammonia and 30–70% of endogas (or natural gas) is recommended for the production of a diffusion layer with a good set of operational properties (for example, with high wear resistance).Moreover, the use of a gaseous atmosphere based on commercial nitrogen (50–90%) with ammonia, natural-gas, oxygen, or carbon dioxide additives is promising for carbonitriding at 700°C. Here, this medium should not contain more 0.5–1.0% of O₂ and 3% of CO₂. The nitrogen-based gaseous atmospheres ensure the attainment of quality diffusion layers with decreased risk of explosion and saving of energy resources.Moscow Automobile Traffic and Highway Construction Institute. Nongovernmental Production Union "All-Union Scientific-Research and Experimental Design Institute for Trade Machine Construction. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 5, pp. 32–36, May, 1987.