Carbide Type Influence on Tribological Properties of Hard Faced Steel Layer Part II- Experimental Results

In this paper is presented a preceding procedure that should be conducted in order to successfully regenerate damaged forging dies by the hard facing process. After the tool damage types identification, as well as their causes, we have chosen the procedure and the parameters of hard facing that we further corrected by conducting the test hard facings on models. Thus, we were able to relate the experimental results outputs with the repair technology, taking as a criterion the quality of the surface layers wear resistance such as friction coefficient and width of hard faced zone, hardness and its distribution in cross section, then microstructure of characteristic of hard faced zones, etc. This research points out significancy of tribological properties of certain types of carbides and their effects on metal matrix, in which carbides are embedded. Our tribological investigations have shown that the working life of the hard faced tool can be longer than that of the new tool

Carbide Type Influence on Tribological Properties of Hard Faced Steel Layer - Part I - Theoretical Considerations

This paper gives a theoretical review of influence of the most important alloying elements on steel, and review of the most important carbide-forming elements and states the conditions which elements should fulfill in order to be considered as carbide-forming. It primarily involves alloying elements which in the iron-carbon system can form simple, complex or special carbides, i.e. phases of interstitial and substitutive type. It also gives a review of carbide types that are formed during either production or reparatory hard facing of steel parts with different types of filler materials

Multi-phonon scattering and Ti-induced hydrogen dynamics in sodium alanate

We use ab initio methods and neutron inelastic scattering (NIS) to study the structure, energetics, and dynamics of pure and Ti-doped sodium alanate (NaAlH_4), focusing on the possibility of substitutional Ti doping. The NIS spectrum is found to exhibit surprisingly strong and sharp two-phonon features. The calculations reveal that substitutional Ti doping is energetically possible. Ti prefers to substitute for Na and is a powerful hydrogen attractor that facilitates multiple Al--H bond breaking. Our results hint at new ways of improving the hydrogen dynamics and storage capacity of the alanates.Comment: 5 pages, with 4 postscript figures embedded. Uses REVTEX4 and graphicx macro

Les rapports du canal mandibulaire avec les faces externes du corps de la mandibule et risques qui en découlent de le léser

The investigations of relations and position of the mandibular canal (CM) were carried out on 80 mandibles (33 dentulous, 27 partly edentulous and 20 completely edentulous).The studies of relations of CM to the sides of mandibular body were accomplished by morphometric analysis of CM on consecutive transversal sections of mandibular body (54 preparations). The relation of the CM to be buccal or to the lingual side is expressed as the distance from the surface of the correspondent side of the mandibular body, which is shown in Table 1. According to these data, the position of the canal is at first proximate to the lingual side, and from the first molar tooth (M1) it approaches the buccal surface of the mandibular body.The position of the entire CM was determined by analysis of mandibular preparations (26) after removing the buccal osseous lamina. These investigations revealed that the position of the CM is predominantly buccal. Reconstruction of relations of the CM to the sides of mandibular body, according to the data obtained from transversal sections, and the real position of the CM are presented in Scheme I.The difference in direction lines of relations and of predominant position of the CM is a consequence of morphological characteristics of mandibular body.Le CM a été étudié sur 80 mandibules (dont 33 avec la denture conservée, 27 peu édentées et 20 totalement édentées). L’analyse morphométrique des rapports du CM a été faite sur les coupes frontales de la mandibule (54). La position du CM en entier a été examinée après la trépanation du corps mandibulaire (26 préparations). La reconstruction des rapports du CM d’après les données obtenues sur les coupes fait apparaître que le canal a d’abord une position linguale, ensuite il croise la M1 et se termine dans une position buccale. Dans la plupart des cas, le CM a, dans la majeure partie de son trajet, une position buccale à cause de la configuration caractéristique du corps mandibulaire

Electronic structure and optical properties of lightweight metal hydrides

We study the electronic structures and dielectric functions of the simple hydrides LiH, NaH, MgH2 and AlH3, and the complex hydrides Li3AlH6, Na3AlH6, LiAlH4, NaAlH4 and Mg(AlH4)2, using first principles density functional theory and GW calculations. All these compounds are large gap insulators with GW single particle band gaps varying from 3.5 eV in AlH3 to 6.5 eV in the MAlH4 compounds. The valence bands are dominated by the hydrogen atoms, whereas the conduction bands have mixed contributions from the hydrogens and the metal cations. The electronic structure of the aluminium compounds is determined mainly by aluminium hydride complexes and their mutual interactions. Despite considerable differences between the band structures and the band gaps of the various compounds, their optical responses are qualitatively similar. In most of the spectra the optical absorption rises sharply above 6 eV and has a strong peak around 8 eV. The quantitative differences in the optical spectra are interpreted in terms of the structure and the electronic structure of the compounds.Comment: 13 pages, 10 figure

La structure osseuse de la branche montante de la mandibule

Osseous structure of the ramus of mandible (RM) is of a practical clinical significance. Osteosynthesis of fractured segments and the success of the sagittal or the horizontal ramus split osteotomy depends on the cortical bone disposition and thickness.After morphometric investigations of the RM, conducted on 70 mandibles of adults, consecutive horizontal and frontal sections were made. On these sections, the cortical layer was studied and the cortical bone thickness was measured at four previously marked points.In the regard of morphometry, the significant datum is that nearly half of all the cases is grouped round the mean value of any parameter.Cortical bone is continuous and its two main sheets are the buccal and the lingual cortical plates. In its entirety, the buccal cortical plate is thicker than the lingual. The thickness of both cortical plates increases in the direction from the coronoid process to the angle of mandible.L’ostéosynthèse de la branche montante de la mandibule et le succès de l’ostéotomie sagittale ou horizontale de cette branche dépendent de la disposition et de l’épaisseur de sa couche osseuse compacte. Les examens morphométriques qui ont été faits sur 70 mandibules des sujets adultes montrent que presque la moitié de tous les cas se groupent autour de la valeur moyenne des paramètres mesurés (schéma 1 et tableau I).Sur les coupes horizontales et frontales, l’épaisseur des lames compactes buccale et linguale a été mesurée dans certains points prédéterminés et il a été établi que la lame buccale est toujours plus épaisse (schéma 2 et tableau II)

Altérations athéroscléreuses de l’artère dentaire inférieure en corrélation avec celles de la bifurcation carotidienne et de l’aorte abdominale

50 corpses from adults aged 20 to 75 have been used in order to study the atherosclerotic lesions occurring in typical regions (bifurcation of the common carotid artery and the abdominal aorta) and their relationship to atherosclerotic changes in the inferior alveolar artery. Histological analysis revealed that atherosclerotic alterations of the inferior alveolar artery may appear sometimes earlier than it would be expected on the ground of age. Intima cell proliferation and thickening of elastic elements in the middle layer of the arterial wall, the first signs of atherosclerosis, were found already at the beginning of the third decade of life when the signs of this process in the typical regions were not yet evident. Atherosclerosis affects essentially the functional capacity of the inferior alveolar artery. The development of atherosclerosis in the wall of this artery favours an hypovascularization of the mandible, which must be of certain importance in every operative procedure in oral surgery, especially in those inducing a severe and long traumatism in bone and soft tissues, such as dental implantations.Cette étude, faite sur 50 cadavres (de 20 à 75 ans) concerne les altérations athéroscléreuses de l’artère dentaire inférieure et leurs rapports avec les altérations athéroscléreuses dans les territoires typiques (bifurcation carotidienne et aorte abdominale). L’examen histologique a fait apparaître que les altérations athéroscléreuses de l’artère dentaire inférieure peuvent être relativement plus évidentes et précoces que l’on ne s’y attendrait compte tenu de l’âge. Une prolifération cellulaire de l’intima et un épaississement de la lame élastique moyenne dans la paroi artérielle, premiers signes de l’athérosclérose, peuvent apparaître dès30 ans, alors que l’on ne trouve pas encore d’altérations de ce type dans les territoires typiques. L’athérosclérose a une influence cruciale sur la capacité fonctionnelle de l’artère dentaire inférieure puisque celle-ci chemine dans le canal osseux, qui empêche sa dilatation. Le développement de l’athérosclérose dans la paroi de cette artère favorise une hypovascularisation de la mandibule, ce qui a une importance certaine lors de toute intervention en chirurgie orale, surtout lorsqu’elle entraîne un traumatisme grave et prolongée de l’os et des parties molles, comme c’est le cas lors de l’insertion d’implants dentaires

Anatomie chirurgicale de la glande sublinguale

Because of its position, the sublingual gland is clinically important especially in the events of injuries and infections in the anterior part of the sublingual region.The morphology and relationships of this gland were studied by dissection methods applied on 80 fresh or formaldehyde fixed preparations of the mouth floor and of the tongue, which were partly (31 preparations) taken out together with the mandible.As for the shape of the gland, three main types were found: 1° the cuneiform type which was the most frequent (71 %), 2° the pyramidal type which was less frequent (16%) and the fusiform type (13%) which comprised the cases of a very elongated gland (up to 65 mm).The space in which the gland lied had four walls. Its internal wall consisted of the mylohyoid muscle and it comprised the hyoglossus muscle as well when the gland was very elongated. The inferior wall consisted of the mylohyoid muscle and sometimes it comprised also a narrow part of the superior surface of the geniohyoglossus muscle. An osseous depression on the internal side of the mandible represented the external wall of the sublingual gland space. The superior wall is clinically the most significant. It consists of the sublingual mucosa and a sublingual fold. This wall represents a main surgical access to the gland. In edentulous mandibles this mucous fold may be at the level of the upper mandibular border which may hinder the use of the lower dental prosthesis.La morphologie et les rapports de la glande sublinguale ont été étudiés par 80 dissections du plancher de la bouche et de la langue.Trois types différents de glandes ont été définis du point de vue forme: le type cunéiforme (71%), le type pyramidal (16%) et le type fusiforme (13%).La loge de la glande sublinguale possède quatre parois: deux (parois inférieure et interne) de nature musculaire, une (paroi externe) de nature osseuse et une (paroi supérieure) de nature muqueuse

Changes in chemical attributes during ripening of traditional fermented sausage, "Pirot ironed"

"Pirot ironed" is a traditional Serbian dry-fermented sausage manufactured in the southeast of Serbia. The changes in the chemical attributes of Pirot ironed sausage were followed during ripening. Samples were taken on the processing days 0, 7, 14, 21 and 28. Pirot ironed sausage was produced from the most valuable cuts of beef and chevon, without addition of starter cultures or fat tissues. Sausages were manufactured in a traditional drying/ripening chamber, where they were pressed every two days to acquire the typical flat form and to speed up the drying. The final water activity was 0.839. The lowest pH value recorded was 5.30 on the processing day 28. During ripening, the water content decreased significantly from 74.72% to 40.32%, while the protein and the fat amounts increased significantly from 19.12% to 45.79% and from 1.22% to 6.21%, respectively. Up to now, the properties of Pirot ironed sausage have not been recognized or published in scientific literature in spite of the long tradition and popularity of this meat product in Serbia